Abstract:
An object is to provide a laser processing device and a laser processing system capable of measuring a distance between a work and a processing head accurately and simply and capable of checking the quality of processing in real time during the processing. Provided are: a photodetector that detects the intensity of a processing laser beam split by optical path splitting means, and outputs a detection signal having a signal intensity responsive to the detected intensity together with a time of detection of the intensity; a signal intensity comparing unit that compares the signal intensities of multiple detection signals received from the photodetector; and a detection time comparing unit that compares times of detection of multiple intensities. The signal intensity comparing unit measures a processing quality by comparing the signal intensity of a detection signal received from the photodetector responsive to an incident beam on a work and the signal intensity of a detection signal received from the photodetector responsive to a reflected beam from the work. The detection time comparing unit measures a distance between a laser processing device and the work by comparing times of detection of the intensities.

Description:
[0001]    This application is based on and claims the benefit of priority from Japanese Patent Application No. 2016-138626, filed on 13 Jul. 2016, the content of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The present invention relates to a laser processing device and a laser processing system for processing of a work using a processing laser beam. 
       Related Art 
       [0003]    For laser processing using a laser processing head, a distance between a work and the processing head has been required to be controlled so as to place a focal position of an optical system on the work. A distance between the processing head and the work has not been maintained constantly, particularly in the application of the processing head to remote laser welding performed with a galvanometer scanner gripped by a robot, for example. Hence, for proper processing, the aforementioned distance has been required to be measured and the focal position has been required to be controlled to conform to the measured distance. Further, ability to check the quality of processing in real time during the processing has been required in terms of reducing takt time and quality management. 
         [0004]    The above-described problem may be solved by a method disclosed by patent document  1 , for example. According to this method, the position of a galvanometer scanner gripped by a robot is measured based on the position of the tip of a hand of the robot. Patent document  2  discloses a method of measuring a distance between a work and a processing head by installing a laser for measurement inside the processing head. There has been a different method of measuring a distance between a work and a processing head by installing a measuring instrument outside the processing head. 
         [0005]    Patent Document 1: Japanese Patent No. 4792901 Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2016-000421 
       SUMMARY OF THE INVENTION 
       [0006]    However, the method of patent document 1 finds it difficult to measure a distance between a work and a processing head accurately in consideration of absolute position accuracy of the robot or repeatability. The method of patent document 2 necessitates installation of a light source for distance measurement inside the processing head separately from a light source for processing. This involves a problem of cost increase and a problem relating to space in the processing head. Regarding the method of installing the measuring instrument outside the processing head, simply measuring a distance between the work and the processing head is made difficult by the necessity to provide the measuring instrument separately. Further, the methods described above have not been devised on condition that the quality of processing be checked in real time during the processing. 
         [0007]    It is therefore an object of the present invention to provide a laser processing device and a laser processing system capable of measuring a distance between a work and a processing head accurately and simply and capable of checking the quality of processing in real time during the processing. 
         [0008]    (1) A laser processing device according to the present invention is a laser processing device (laser processing device  100  described later, for example) for processing of a work using a processing laser beam. The laser processing device comprises: at least one optical path splitting means (optical path splitting means  110 - 1 ,  110 - 2 ,  110 - 3 ,  110 - 4  described later, for example) that splits the processing laser beam; a photodetector (photodetector  130  described later, for example) that detects the intensity of the processing laser beam split by the optical path splitting means, and outputs a detection signal having a signal intensity responsive to the detected intensity together with a time of detection of the intensity; a signal intensity comparing unit (signal intensity comparing unit  140  described later, for example) that compares the signal intensities of multiple detection signals each being the detection signal received from the photodetector; and a detection time comparing unit (detection time comparing unit  150  described later, for example) that compares times of detection of multiple intensities each being the intensity received from the photodetector. The signal intensity comparing unit measures a processing quality by comparing the signal intensity of a detection signal received from the photodetector responsive to an incident beam on the work resulting from splitting by the optical path splitting means and the signal intensity of a detection signal received from the photodetector responsive to a reflected beam from the work resulting from splitting by the optical path splitting means. The detection time comparing unit measures a distance between the laser processing device and the work by comparing a time of detection of an intensity received from the photodetector responsive to the incident beam and a time of detection of an intensity received from the photodetector responsive to the reflected beam. 
         [0009]    (2) In the laser processing device according to (1), the photodetector (photodetector  330 - 1 ,  330 - 2  described later, for example) of the laser processing device (laser processing device  300  described later, for example) may include two or more photodetectors, at least one of the photodetectors may detect the intensity of the incident beam, and at least one of the photodetectors may detect the intensity of the reflected beam. 
         [0010]    (3) In the laser processing device according to (1) or (2), the signal intensity comparing unit (signal intensity comparing unit  140 ,  340  described later, for example) may measure a difference or a ratio between the signal intensity of the detection signal responsive to the incident beam and the signal intensity of the detection signal responsive to the reflected beam. 
         [0011]    (4) A first laser processing system according to the present invention (laser processing system  200  described later, for example) comprises a laser oscillator (laser oscillator  220  described later, for example), an oscillator controller (oscillator controller  210  described later, for example) that controls the laser oscillator, and a laser processing device (laser processing device  230  described later, for example) for processing of a work using a processing laser beam oscillated by the laser oscillator. The laser processing device comprises: at least one optical path splitting means (optical path splitting means  240 - 1 ,  240 - 2 ,  240 - 3 ,  240 - 4  described later, for example) that splits the processing laser beam; and a photodetector (photodetector  260  described later, for example) that detects the intensity of the processing laser beam split by the optical path splitting means, and outputs a detection signal having a signal intensity responsive to the detected intensity together with a time of detection of the intensity. The laser processing system further comprises a signal intensity comparing device (signal intensity comparing device  270  described later, for example) and a detection time comparing device (detection time comparing device  280  described later, for example). The signal intensity comparing device compares the signal intensities of multiple detection signals each being the detection signal received from the photodetector. The detection time comparing device compares times of detection of multiple intensities each being the intensity received from the photodetector. The signal intensity comparing device measures a processing quality by comparing the signal intensity of a detection signal received from the photodetector responsive to an incident beam on the work resulting from splitting by the optical path splitting means and the signal intensity of a detection signal received from the photodetector responsive to a reflected beam from the work resulting from splitting by the optical path splitting means. The detection time comparing device measures a distance between the laser processing device and the work by comparing a time of detection of an intensity received from the photodetector responsive to the incident beam and a time of detection of an intensity received from the photodetector responsive to the reflected beam. 
         [0012]    (5) In the laser processing system according to (4), the photodetector of the laser processing device may include two or more photodetectors, at least one of the photodetectors may detect the intensity of the incident beam, and at least one of the photodetectors may detect the intensity of the reflected beam. 
         [0013]    (6) A second laser processing system according to the present invention (laser processing system  400  described later, for example) comprises a laser oscillator (laser oscillator  420  described later, for example), an oscillator controller (oscillator controller  410  described later, for example) that controls the laser oscillator, and a laser processing device (laser processing device  430  described later, for example) for processing of a work using a processing laser beam oscillated by the laser oscillator. The laser processing device comprises: at least one optical path splitting means (optical path splitting means  440  described later, for example) that splits the processing laser beam; and a photodetector (photodetector  460  described later, for example) that detects the intensity of the processing laser beam split by the optical path splitting means, and outputs a detection signal having a signal intensity responsive to the detected intensity together with a time of detection of the intensity. The laser processing system further comprises a signal intensity comparing device (signal intensity comparing device  470  described later, for example) and a detection time comparing device (detection time comparing device  480  described later, for example). The signal intensity comparing device compares the signal intensity of the detection signal received from the photodetector with an intensity command value transmitted from the oscillator controller to the laser oscillator. The detection time comparing device compares the time of detection of the intensity received from the photodetector with an oscillation command time transmitted from the oscillator controller to the laser oscillator. The signal intensity comparing device measures a processing quality by comparing the signal intensity of the detection signal received from the photodetector responsive to a reflected beam from the work resulting from splitting by the optical path splitting means with the intensity command value. The detection time comparing device measures a distance between the laser processing device and the work by comparing the time of detection of the intensity received from the photodetector responsive to the reflected beam with the oscillation command time. 
         [0014]    (7) In the laser processing system described in (4) to (6), the signal intensity comparing device may measure a difference or a ratio between the signal intensity of the detection signal responsive to the incident beam or the intensity command value and the signal intensity of the detection signal responsive to the reflected beam. 
         [0015]    According to the present invention, by using a light source for processing as a light source for measurement, a distance between a work and a processing head can be measured and a processing quality can be checked at the same time. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  shows the configuration of a laser processing device entirely according to a first embodiment; 
           [0017]      FIG. 2  shows the configuration of a laser processing system entirely according to a second embodiment; 
           [0018]      FIG. 3  shows the configuration of a laser processing device entirely according to a third embodiment; and 
           [0019]      FIG. 4  shows the configuration of a laser processing system entirely according to a fourth embodiment. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First Embodiment 
       [0020]    A first embodiment of the present invention will be described in detail by referring to  FIG. 1 . 
         [0021]    For laser processing using a laser processing device, grasping the position of the laser processing device and that of a work relative to each other is important for obtaining a favorable processing quality. According to the present invention, to calculate a distance between the laser processing device and the work, a time of flight (TOF) method is employed by using a processing light source. More specifically, this method is to measure time of flight of a processing beam from projection of the processing beam to a subject to receipt of a reflected beam, and to multiply the measured time of flight by the speed of flight of the processing beam. Optical path splitting means such as a beam splitter is installed for measurement of the time of flight. According to the first embodiment, an incident beam on a work and a reflected beam from the work both resulting from splitting by the optical path splitting means are measured, and a distance is measured based on a difference between times of detection of these beams. A photodetector capable of detecting a light intensity is used for measurement of the incident beam on the work and the reflected beam from the work. A time difference between incidence of the incident beam on the photodetector and incidence of the reflected beam on the photodetector is determined using times of detection of these beams. Further, by comparing a detected intensity of the incident beam on the work and that of the reflected beam from the work, change in the intensity of the reflected beam relative to the incident beam can be measured, so that a processing quality can be measured based on the state of the reflected beam. 
         [0022]      FIG. 1  shows an example of the configuration of a laser processing device  100  according to the first embodiment. The laser processing device  100  includes four optical path splitting means including  110 - 1 ,  110 - 2 ,  110 - 3 , and  110 - 4  (these means are collectively called “optical path splitting means  110 ”), a focusing lens  120 , a photodetector  130 , a signal intensity comparing unit  140 , and a detection time comparing unit  150 . 
         [0023]    The optical path splitting means  110  is an optical element that splits a beam in a constant ratio into a transmitted beam and a reflected beam. As described above, a beam splitter is usable as the optical path splitting means  110 , for example. The center of each of the four optical path splitting means  110 - 1  to  110 - 4  forms a rectangle. Each of the four optical path splitting means  110 - 1  to  110 - 4  is arranged in such a manner that a normal to each of the front surface and the back surface of each optical path splitting means, viewed from an incident beam or from a reflected beam, forms an angle of 45 degrees or 135 degrees with a side of the above-described rectangle. The photodetector  130  includes a photo-detecting unit not shown in the drawings arranged on a straight light passing through the center of the optical path splitting means  110 - 1  and that of the optical path splitting means  110 - 2  and on an opposite side of the optical path splitting means  110 - 1  across the optical path splitting means  110 - 2 . The center of the focusing lens  120  is arranged on a straight line passing through the center of the optical path splitting means  110 - 1  and that of the optical path splitting means  110 - 3  and on an opposite side of the optical path splitting means  110 - 1  across the optical path splitting means  110 - 3 . 
         [0024]    A laser oscillator and an oscillator controller that controls the laser oscillator, both of which are not shown in the drawings, are provided outside the laser processing device  100 . A laser beam emitted from the laser oscillator and incident on the laser processing device  100  first reaches the optical path splitting means  110 - 1 . Then, the laser beam is partially transmitted through the optical path splitting means  110 - 1  and the other of the laser beam is reflected. The incident beam reflected from the optical path splitting means  110 - 1  is transmitted through the optical path splitting means  110 - 2  to enter the photodetector  130 . The incident beam transmitted through the optical path splitting means  110 - 1  passes through the optical path splitting means  110 - 3  and the focusing lens  120  to collide with a work  500 . A beam reflected from the work  500  passes through the focusing lens  120 . Then, the reflected beam is reflected from each of the optical path splitting means  110 - 3 , the optical path splitting means  110 - 4 , and the optical path splitting means  110 - 2  to reach the photodetector  130 . By following the above-described routes, both the incident beam on the work  500  and the reflected beam from the work  500  enter the photodetector  130 . 
         [0025]    The photodetector  130  detects the intensities of both of the following beams having entered the photodetector  130 : the incident beam on the work  500  and the reflected beam from the work  500 . The photodetector  130  outputs a detection signal having a signal intensity responsive to the intensity of the incident beam on the work  500  together with a time of detection of this intensity. Further, the photodetector  130  outputs a detection signal having a signal intensity responsive to the intensity of the reflected beam from the work  500  together with a time of detection of this intensity. For example, a photodiode is usable as the photodetector  130 . 
         [0026]    The signal intensity comparing unit  140  compares the following signal intensities received from the photodetector  130 : the signal intensity of the detection signal responsive to the incident beam on the work  500  and the signal intensity of the detection signal responsive to the reflected beam from the work  500 . Based on a result of this comparison, the signal intensity comparing unit  140  measures the processing quality of laser processing. More specifically, the signal intensity comparing unit  140  makes this comparison by calculating a difference or a ratio between the signal intensity of the detection signal responsive to the incident beam and the signal intensity of the detection signal responsive to the reflected beam. 
         [0027]    The detection time comparing unit  150  compares the following detection times received from the photodetector  130 : the time of detection of the intensity of the incident beam on the work  500  and the time of detection of the intensity of the reflected beam from the work  500 . Based on a result of this comparison, the detection time comparing unit  150  calculates a distance between the laser processing device  100  and the work  500 . More specifically, the detection time comparing unit  150  can calculate this distance by determining a time difference between the time of detection of the intensity of the incident beam on the work  500  and the time of detection of the intensity of the reflected beam from the work  500 , and using a result of multiplication of the determined time difference by the speed of a processing laser beam. 
         [0028]    The operation of the laser processing device  100  as a whole is as follows. If a processing laser beam emitted from the laser oscillator provided outside the laser processing device  100  enters the laser processing device  100 , the multiple optical path splitting means  110  split the incident processing laser beam into a beam to be incident on the work  500  and a beam to be reflected from the work  500 . Both of these processing laser beams enter the photodetector  130 . The signal intensity comparing unit  140  compares the signal intensities of the detection signals responsive to the following beams having entered the photodetector  130 : the incident beam on the work  500  and the reflected beam from the work  500 . A processing quality can be checked based on a result of this comparison. The detection time comparing unit  150  compares the time of detection of the intensity of the incident beam on the work  500  and the time of detection of the intensity of the reflected beam from the work  500 . A distance between the laser processing device  100  and the work  500  can be measured based on a result of this comparison. 
         [0029]    According to the above-described first embodiment, a distance between the laser processing device  100  and the work  500  can be calculated without the need of preparing a light source for distance measurement separately from a light source for processing or a device for distance measurement separately from the laser processing device. Further, a processing quality can be evaluated together with distance measurement. 
       Second Embodiment 
       [0030]    A second embodiment of the present invention will be described in detail by referring to  FIG. 2 . 
         [0031]    According to the first embodiment, the laser processing device  100  includes the signal intensity comparing unit  140  and the detection time comparing unit  150  as its constituting elements. By contrast, according to the second embodiment, instead of providing a signal intensity comparing unit and a detection time comparing unit to the laser processing device  100 , a signal intensity comparing device  270  and a detection time comparing device  280  separately from the laser processing device  100  are provided. 
         [0032]    More specifically, a laser processing system  200  with a laser processing device  230  according to the second embodiment includes a laser oscillator  220 , an oscillator controller  210  that controls the laser oscillator  220 , the signal intensity comparing device  270 , and the detection time comparing device  280  in addition to the laser processing device  230 . 
         [0033]    Like the laser processing device  100  according to the first embodiment, the laser processing device  230  includes four optical path splitting means including  240 - 1 ,  240 - 2 ,  240 - 3 , and  240 - 4  (these means are collectively called “optical path splitting means  240 ”), a focusing lens  250 , and a photodetector  260 . These constituting elements are arranged in the same positions as those of the corresponding constituting elements of the laser processing device  100 . 
         [0034]    A route of a processing laser beam, the function and the operation of the optical path splitting means  240 , those of the focusing lens  250 , and those of the photodetector  260  are the same as those of the first embodiment, so that they will not be described here. The function and the operation of the signal intensity comparing device  270  and those of the detection time comparing device  280  are the same as those of the signal intensity comparing unit  140  and those of the detection time comparing unit  150  respectively, so that they will not be described here. 
         [0035]    The operation of the laser processing system  200  as a whole is as follows. If a processing laser beam emitted from the laser oscillator  220  provided outside the laser processing device  230  enters the laser processing device  230 , the multiple optical path splitting means  240  split the incident processing laser beam into a beam to be incident on the work  500  and a beam to be reflected from the work  500 . Both of these processing laser beams enter the photodetector  260 . The signal intensity comparing device  270  provided outside the laser processing device  230  compares the signal intensities of detection signals responsive to the following beams having entered the photodetector  260 : the incident beam on the work  500  and the reflected beam from the work  500 . A processing quality can be checked based on a result of this comparison. The detection time comparing device  280  provided outside the laser processing device  230  compares a time of detection of the intensity of the incident beam on the work  500  and a time of detection of the intensity of the reflected beam from the work  500 . A distance between the laser processing device  230  and the work  500  can be measured based on a result of this comparison. 
         [0036]    According to the second embodiment, like in the first embodiment, a distance between the laser processing device  230  and the work  500  can be calculated without the need of preparing a light source for distance measurement separately from a light source for processing. Further, a processing quality can be evaluated together with distance measurement. 
       Third Embodiment 
       [0037]    A third embodiment of the present invention will be described in detail by referring to  FIG. 3 . 
         [0038]    The laser processing device according to each of the first and second embodiments includes the multiple optical path splitting means. By contrast, a laser processing device according to the third embodiment includes only one optical path splitting means and includes multiple photodetectors. 
         [0039]      FIG. 3  shows an example of the configuration of a laser processing device  300  according to the third embodiment. The laser processing device  300  includes optical path splitting means  310 , a focusing lens  320 , a photodetector  330 - 1 , a photodetector  330 - 2 , a signal intensity comparing unit  340 , and a detection time comparing unit  350 . 
         [0040]    Only one optical path splitting means  310  is provided in the laser processing device  300 . Both the front surface and the back surface of the optical path splitting means  310 , viewed from an incident beam or from a reflected beam, function as reflection surfaces. The optical path splitting means  310  is arranged in such a manner that a normal to each of the front surface and the back surface of the optical path splitting means  310  forms an angle of  45  degrees with the incident beam or the reflected beam. Referring to  FIG. 3 , on the assumption that a processing laser beam is to enter the laser processing device  300  from above as viewed from the optical path splitting means  310 , the photodetector  330 - 1 , the photodetector  330 - 2 , and the focusing lens  320  are arranged to the left and to the right of the optical path splitting means  310 , and below the optical path splitting means  310  respectively. 
         [0041]    A laser oscillator and an oscillator controller that controls the laser oscillator, both of which are not shown in the drawings, are provided outside the laser processing device  300 . A laser beam emitted from the laser oscillator and incident on the laser processing device  300  first reaches the optical path splitting means  310 . Then, the laser beam is partially transmitted through the optical path splitting means  310  and the other of the laser beam is reflected. The incident beam reflected from the optical path splitting means  310  enters the photodetector  330 - 1 . The incident beam transmitted through the optical path splitting means  310  passes through the focusing lens  320  to collide with the work  500 . A beam reflected from the work  500  passes through the focusing lens  320 . Then, the reflected beam is reflected from the optical path splitting means  310  to reach the photodetector  330 - 2 . 
         [0042]    The photodetector  330 - 1  detects the intensity of the incident beam on the work  500  having entered the photodetector  330 - 1 . The photodetector  330 - 1  outputs a detection signal having a signal intensity responsive to the intensity of the incident beam on the work  500  together with a time of detection of this intensity. The photodetector  330 - 2  detects the intensity of the reflected beam from the work  500  having entered the photodetector  330 - 2 . The photodetector  330 - 2  outputs a detection signal having a signal intensity responsive to the intensity of the reflected beam from the work  500  together with a time of detection of this intensity. 
         [0043]    The signal intensity comparing unit  340  compares the signal intensity of the detection signal responsive to the incident beam on the work  500  received from the photodetector  330 - 1  and the signal intensity of the detection signal responsive to the reflected beam from the work  500  received from the photodetector  330 - 2 . Based on a result of this comparison, the signal intensity comparing unit  340  measures the processing quality of laser processing. More specifically, the signal intensity comparing unit  340  makes this comparison by calculating a difference or a ratio between the signal intensity of the detection signal responsive to the incident beam and the signal intensity of the detection signal responsive to the reflected beam. 
         [0044]    The detection time comparing unit  350  compares the time of detection of the intensity of the incident beam on the work  500  received from the photodetector  330 - 1  and the time of detection of the intensity of the reflected beam from the work  500  received from the photodetector  330 - 2 . Based on a result of this comparison, the detection time comparing unit  350  calculates a distance between the laser processing device  300  and the work  500 . More specifically, the detection time comparing unit  350  can calculate this distance by determining a time difference between the time of detection of the intensity of the incident beam on the work  500  and the time of detection of the intensity of the reflected beam from the work  500 , and using a result of multiplication of the determined time difference by the speed of a processing laser beam. 
         [0045]    The operation of the laser processing device  300  as a whole is as follows. If a processing laser beam emitted from the laser oscillator provided outside the laser processing device  300  enters the laser processing device  300 , the single optical path splitting means  310  splits the incident processing laser beam into a beam to be incident on the work  500  and a beam to be reflected from the work  500 . The incident beam on the work  500  enters the photodetector  330 - 1 . The reflected beam from the work  500  enters the photodetector  330 - 2 . The signal intensity comparing unit  340  compares the signal intensity of the detection signal responsive to the incident beam on the work  500  having entered the photodetector  330 - 1  and the signal intensity of the detection signal responsive to the reflected beam from the work  500  having entered the photodetector  330 - 2 . A processing quality can be checked based on a result of this comparison. The detection time comparing unit  350  compares the time of detection of the intensity of the incident beam on the work  500  having entered the photodetector  330 - 1  and the time of detection of the intensity of the reflected beam from the work  500  having entered the photodetector  330 - 2 . A distance between the laser processing device  300  and the work  500  can be measured based on a result of this comparison. 
         [0046]    According to the above-described third embodiment, a distance between the laser processing device  300  and the work  500  can also be calculated without the need of preparing a light source for distance measurement separately from a light source for processing or a device for distance measurement separately from the laser processing device. Further, a processing quality can be evaluated together with distance measurement. Additionally, unlike in the first and second embodiments, the intensity and the time of receipt of the incident beam and those of the reflected beam can be acquired by using only one optical path splitting means. 
       Fourth Embodiment 
       [0047]    A fourth embodiment of the present invention will be described in detail by referring to  FIG. 4 . 
         [0048]    According to the first to third embodiments, both the intensity of an incident beam on the work  500  and that of a reflected beam from the work  500  are detected. Based on results of the detection about these beams, a processing quality and a distance between a laser processing device and a work are measured. According to the fourth embodiment, instead of using a result of detection about the intensity of an incident beam, an intensity command value and an oscillation command time of an incident beam contained in oscillation command information transmitted from an oscillator controller to a laser oscillator are acquired. Each of the acquired intensity command value and oscillation command time is compared with a result of detection about the intensity of a reflected beam to measure a processing quality and a distance between a laser processing device and a work. 
         [0049]      FIG. 4  shows an example of the configuration of a laser processing system  400  with a laser processing device  430  according to the fourth embodiment. The laser processing system  400  includes a laser oscillator  420 , an oscillator controller  410  that controls the laser oscillator  420 , a signal intensity comparing device  470 , and a detection time comparing device  480  in addition to the laser processing device  430 . 
         [0050]    Like the laser processing device  300  according to the third embodiment, the laser processing device  430  according to the fourth embodiment includes single optical path splitting means  440 . The optical path splitting means  440  is arranged in such a manner that a normal to each of the front surface and the back surface of the optical path splitting means  440  forms an angle of 45 degrees with an incident beam or a reflected beam. Unlike the laser processing device  300  according to the third embodiment, the laser processing device  430  according to the fourth embodiment does not include a photodetector that detects an incident beam on the work  500  but only a photodetector  460  that detects a reflected beam from the work  500  is provided. Specifically, referring to  FIG. 4 , on the assumption that a processing laser beam is to enter the laser processing device  430  from above as viewed from the optical path splitting means  440 , constituting elements include only the photodetector  460  arranged to the right of the optical path splitting means  440  and a focusing lens  450  arranged below the optical path splitting means  440  in addition to the optical path splitting means  440 . The photodetector  460  detects the intensity of the reflected beam from the work  500  having entered the photodetector  460 . The photodetector  460  outputs a detection signal having a signal intensity responsive to the intensity of the reflected beam from the work  500  together with a time of detection of this intensity. 
         [0051]    Unlike in the laser processing system  200  according to the second embodiment, in the laser processing system  400  according to the fourth embodiment, the oscillator controller  410  transmits an oscillation command containing information about an intensity command value and an oscillation command time of an incident beam to each of the signal intensity comparing device  470  and the detection time comparing device  480  as well as to the laser oscillator  420 . 
         [0052]    The signal intensity comparing device  470  compares the signal intensity of the detection signal responsive to the reflected beam from the work  500  received from the photodetector  460  and the intensity command value of the incident beam on the work  500  received from the oscillator controller  410 . Based on a result of this comparison, the signal intensity comparing device  470  measures the processing quality of laser processing. 
         [0053]    The detection time comparing device  480  compares the time of detection of the intensity of the reflected beam from the work  500  received from the photodetector  460  and the oscillation command time of the incident beam on the work  500  received from the oscillator controller  410 . Based on a result of this comparison, the detection time comparing device  480  calculates a distance between the laser processing device  430  and the work  500 . More specifically, the detection time comparing device  480  can calculate this distance by determining a time difference between the oscillation command time of the incident beam on the work  500  and the time of detection of the intensity of the reflected beam from the work  500 , and using a result of multiplication of the determined time difference by the speed of a processing laser beam. 
         [0054]    The operation of the laser processing system  400  as a whole is as follows. If a processing laser beam emitted from the laser oscillator  420  provided outside the laser processing device  430  enters the laser processing device  430 , the single optical path splitting means  440  splits the incident processing laser beam into a beam to be incident on the work  500  and a beam to be reflected from the work  500 . The reflected beam from the work  500  enters the photodetector  460 . The signal intensity comparing device  470  compares the signal intensity of the detection signal responsive to the reflected beam from the work  500  having entered the photodetector  460  and the intensity command value of the incident beam on the work  500  received from the oscillator controller  410 . A processing quality can be checked based on a result of this comparison. The detection time comparing device  480  compares the time of detection of the intensity of the reflected beam from the work  500  having entered the photodetector  460  and the oscillation command time of the incident beam on the work  500  received from the oscillator controller  410 . A distance between the laser processing device  430  and the work  500  can be measured based on a result of this comparison. 
         [0055]    According to the above-described fourth embodiment, a distance between the laser processing device  430  and the work  500  can also be calculated without the need of preparing a light source for distance measurement separately from a light source for processing or a device for distance measurement separately from the laser processing device. Further, a processing quality can be evaluated together with distance measurement. Additionally, the intensity and the time of receipt of the incident beam and those of the reflected beam can be acquired by using only one optical path splitting means unlike in the first and second embodiments, and by using only one photodetector unlike in the third embodiment. 
         [0056]    The present invention is not limited to the embodiments described above. The effects described in the present embodiments are merely given to list most preferable effects achieved by the present invention. Effects achieved by the present invention are not to be limited to those described in the present embodiments. 
         [0057]    A method of processing using the laser processing devices  100 ,  230 ,  300 , and  430 , and the laser processing systems  200  and  400  is realized by software. If this method is to be realized by software, programs for configuring this software are installed on a computer (laser processing device  100 ,  230 ,  300 , or  430 ). These programs may be recorded on a removable medium and then distributed to a user. Alternatively, these programs may be distributed to the user by being downloaded to a computer of the user through a network. Still alternatively, these programs may be provided to the computer of the user (laser processing device  100 ,  230 ,  300 , or  430 ) in the form of web service offered through a network without being downloaded on the computer. 
       EXPLANATION OF REFERENCE NUMERALS 
       [0058]      100 ,  230 ,  300 ,  430  Laser processing device 
         [0059]      110 - 1 ,  110 - 2 ,  110 - 3 ,  110 - 4 ,  240 - 1 ,  240 - 2 ,  240 - 3 ,  240 - 4 ,  310 ,  440  Optical path splitting means 
         [0060]      120 ,  250 ,  320 ,  450  Focusing lens 
         [0061]      130 ,  260 ,  330 - 1 ,  330 - 2 ,  460  Photodetector 
         [0062]      140 ,  340  Signal intensity comparing unit 
         [0063]      150 ,  350  Detection time comparing unit 
         [0064]      200 ,  400  Laser processing system 
         [0065]      210 ,  410  Oscillator controller 
         [0066]      220 ,  420  Laser oscillator 
         [0067]      270 ,  470  Signal intensity comparing device 
         [0068]      280 ,  480  Detection time comparing device 
         [0069]      500  Work