JP2010046669A - Laser beam machining apparatus and laser beam machining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining apparatus and a laser beam machining method, capable of continuing the laser beam machining without detachment of a focus servo even when an abnormal part is formed on a surface of an object OB to be machined and reducing losses of the object OB to be machined and waste of the machining time. <P>SOLUTION: Laser beam for inspection is applied to the forward position in the machining direction of a beam spot of laser beam for machining, and any abnormal part at the position immediately before the laser beam machining is detected based on the intensity of its reflected beam. When the intensity of the reflected beam of the laser beam for inspection is reduced, the mask signal is generated by a mask signal generation circuit 67. A delay circuit 68 prepares the hold signal taking into consideration the time delay before the laser beam for machining is applied to the abnormal part, and outputs it to a conduction circuit 68. When the hold signal is input, the conduction circuit 63 sets the focus error signal to be zero, and holds the focus servo. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus and a laser processing method for irradiating a processing target with laser light to form fine pits, continuous grooves, or reaction traces on the surface of the processing target.

2. Description of the Related Art Conventionally, there is known a laser processing apparatus that collects and irradiates a processing target with laser light with an objective lens to form fine pits, continuous grooves, or reaction traces on the surface of the processing target. In such a laser processing apparatus, for example, as shown in Patent Document 1, reflected light from the processing surface of the workpiece is guided to a light receiver, and based on a light reception signal output from the light receiver, for example, By detecting the amount of defocus by calculation using the astigmatism method, and driving the objective lens in the optical axis direction according to the defocus amount, the focus servo always keeps the focus of the laser beam on the surface of the workpiece. Control is in progress. By performing such focus servo control, even if the surface height of the object to be processed fluctuates, it becomes possible to always focus the laser beam on the surface of the object to be processed, and to perform laser processing with high accuracy.
Japanese Patent Laid-Open No. 11-203735

  However, when a foreign object adheres to the surface of the workpiece or a scratch is formed, focus servo control may be disabled. This is because the distance between the objective lens and the surface of the object to be processed (surface of the abnormal part) changes greatly when the irradiation position of the laser light enters the abnormal part of the surface of the object to be processed (foreign matter adhesion part, groove forming part). This is because the amount of change may exceed the controllable range of the focal position.

  Here, the controllable range of the focal position will be described. FIG. 16 shows a waveform of a focus error signal obtained by calculation by the astigmatism method when the distance x between the objective lens and the surface of the workpiece is changed in the optical axis direction of the laser beam. This focus error signal has an S-shaped waveform as shown. When the objective lens is moved in a direction away from the object to be processed from a state close to the surface of the object to be processed, the focus error signal once decreases from the zero level and then increases and crosses the zero level. The point where the zero-cross point P0 is detected is the point where the focal position of the laser beam coincides with the surface of the workpiece. When the objective lens is further moved away from the workpiece, the focus error signal increases and then decreases to zero level.

  In the focus servo control, the position of the objective lens is controlled so that the focus error signal maintains the zero cross point P0. The distance x between the objective lens and the surface of the workpiece is a positive / negative peak point in FIG. If it is outside the area between P1 and P2 (hereinafter, this area is called the S-shaped detection area, and the distance between the peak points is called the S-shaped detection distance), the focus servo control based on the focus error signal is performed. It becomes impossible. That is, the S-shaped detection area is a controllable range of the focal position.

  When performing focus servo control with good followability with respect to the displacement in the optical axis direction of the surface of the workpiece, the S-shaped detection area is set very narrow. Therefore, if there is an abnormal part having a predetermined height or more on the surface of the processing object, the surface position of the processing object deviates from the S-shaped detection area, and focus servo control based on the focus error signal becomes impossible. This phenomenon is called out of focus servo. Once the focus servo is removed in this way, the focus servo control cannot be resumed even if the irradiation position of the laser beam passes through the abnormal portion, and thereafter normal laser processing cannot be performed. For this reason, it is necessary to dispose of the processing object. In addition, the time required for laser processing up to that time is wasted.

  The present invention has been made in order to cope with the above problem, and even if an abnormal portion exists on the surface of the processing object, the laser processing can be continued without losing the focus servo, and the processing object can be lost or processed. The purpose is to reduce the waste of time.

  In order to achieve the above object, a feature of the present invention is that it includes a set unit for setting a workpiece, a rotating means for rotating the set unit, and a processing laser light source. The processing head for condensing the emitted processing laser light by an objective lens and irradiating the processing target, and the irradiation position of the processing laser light are rotated on the surface of the processing target. Controlling the operations of the feed means for changing the relative position between the set portion and the machining head, the rotating means and the feed means so as to move in a direction orthogonal to the irradiation movement locus formed by Meanwhile, laser processing control means for laser processing the surface of the processing object by outputting a driving signal to the processing laser light source and irradiating the surface of the processing object with the processing laser light; Based on the reflected light of the processing laser light from the processing object, the objective lens is placed on the optical axis of the processing laser light so that the focal position of the processing laser light coincides with the surface of the processing object. In a laser processing apparatus including a focus servo unit that performs focus servo control by driving in a direction, the processing head rotates in a rotation direction of the rotation unit relative to a position where the processing laser beam is irradiated onto the processing target An inspection laser light source for irradiating a position immediately before laser processing on the opposite side of the laser processing, and when performing laser processing by the laser processing control means, a drive signal is output to the inspection laser light source, and the processing Inspection laser light irradiation control means for emitting from the inspection laser light source the intensity of inspection laser light that does not cause laser processing of the surface of the object, and the surface of the object to be processed Based on the intensity of the reflected light detected by the light detecting means that detects the intensity of the reflected light of the irradiated inspection laser light, the state of the reflected light of the inspection laser light is out of the normal range. An abnormal period detecting means for detecting the abnormal period being detected, and a control mode switching period in which an end time later than the end time of the abnormal period is set based on the abnormal period detected by the abnormal period detecting means During the switching period setting unit and the control mode switching period set by the switching period setting unit, the control mode of the focus servo unit is switched from the normal mode to the abnormality detection mode, and the position of the objective lens is held. Alternatively, it is possible to perform a focus servo control in which the control range of the focal position of the processing laser beam is wider than that in the normal mode. It has a step.

  In the present invention, a processing head having a processing laser light source and an inspection laser light source is provided, and laser light is irradiated from the processing head onto the surface of the processing target set (fixed) in the set unit. The irradiation position of the laser beam is moved by the operation of the rotating means and the feeding means. The rotation means moves the irradiation position of the laser beam around the rotation axis of the set unit by rotating the set unit. The feeding means changes the relative position between the setting unit and the machining head and moves the irradiation position in a direction orthogonal to the irradiation movement locus formed by the rotation of the setting unit. In this case, the processing head may be moved while the set portion is fixed, the set portion may be moved while the processing head is fixed, or both may be moved. As the set unit, for example, a disk-shaped table for mounting and fixing a plate-like workpiece, or a drum-like fixture that rotates around a cylindrical axis by winding a film-like workpiece around a cylindrical outer peripheral surface Etc. can be used. The feed direction of the feed means (the relative movement direction between the set portion and the machining head) is the table radial direction in the case of a disk-shaped table, and the drum rotation axis direction in the case of a drum-shaped fixture.

  The laser processing control means outputs a drive signal to the processing laser light source while controlling the operations of the rotating means and the feeding means. Thereby, the surface of the workpiece is laser processed. For example, fine pits (intermittently formed grooves), continuous grooves, or reaction traces for forming them (parts that vary depending on the developer) are formed on the surface of the workpiece. During this laser processing, the inspection laser light irradiation control means outputs a drive signal to the inspection laser light source. This inspection laser light is irradiated to a position immediately before laser processing which is on the opposite side of the rotation direction of the rotating means from the position where the processing laser light is irradiated to the object to be processed. Further, the inspection laser light is set to have a lower intensity than the processing laser light so that the processing object does not change even if it is irradiated on the surface of the processing object.

  The light detection means detects the intensity of the reflected light of the inspection laser light irradiated on the surface of the workpiece. The abnormal period detecting means detects an abnormal period in which the state of the reflected light of the inspection laser light is out of the normal range based on the intensity of the reflected light detected by the light detecting means. For example, based on a comparison between the intensity of the reflected light detected by the light detection means and a reference intensity that serves as a threshold for determining a preset abnormality, the intensity of the reflected light deviates from the normal range with the reference intensity as a boundary. Detect an abnormal period. If there is an abnormal part (foreign matter adhering part, flaw forming part) on the surface of the workpiece, the intensity of the reflected light changes when the inspection laser light irradiates the abnormal part. For this reason, for example, a reference intensity is set in advance as a threshold for abnormality determination, and an abnormal portion of the workpiece can be detected by comparing the intensity of the reflected light of the inspection laser light with the reference intensity. . In addition, for example, by providing a light detection means that divides a light receiving region that receives reflected light of the inspection laser light into a plurality of calculation results obtained by an arithmetic expression using the intensity of the reflected light detected in each light receiving region, An abnormal period in which the state of the reflected light of the inspection laser light is out of the normal range may be detected by comparing with a reference value for determining abnormality. In addition, for example, the value of the reflected light of the inspection laser light detected by the light detection means is compared with the reference value for determining abnormality and the reflected light state of the inspection laser light is compared. An abnormal period in which is outside the normal range may be detected.

  When the irradiation position of the inspection laser light passes through the abnormal part, the state (for example, intensity) of the reflected light returns to the normal range. Accordingly, the abnormal period detection means is a period from when the irradiation position of the inspection laser light enters the abnormal portion to when it passes through the abnormal portion (period from when the inspection laser light starts to irradiate the abnormal portion to when irradiation ends). Detect as an abnormal period. Since the inspection laser light irradiates the position immediately before laser processing, the abnormal portion is irradiated earlier than the timing at which the processing laser light actually starts irradiating the abnormal portion. Therefore, it is possible to grasp in advance the timing at which the processing laser beam starts irradiating the abnormal portion and the timing at which the abnormal portion is completely irradiated, by the abnormal period detected by the abnormal period detecting means.

  Therefore, the switching period setting unit sets a control mode switching period in which an end time later than the end time of the abnormal period is set based on the abnormal period detected by the abnormal period detection unit. Then, the control mode switching means switches the control mode of the focus servo means from the normal mode to the abnormality detection mode during the control mode switching period set by the switching period setting means, and holds the position of the objective lens (objective The lens position does not fluctuate), or focus servo control with a wider control range of the focal position of the processing laser beam than in the normal mode is performed. Thereby, before the processing laser beam irradiates the abnormal portion, the control mode of the focus servo means can be switched to the abnormality detection mode, and the focus servo can be prevented from being lost. Moreover, since the abnormality detection mode can be maintained until the irradiation position of the processing laser light passes through the abnormal part, the control mode can be returned to the normal mode at an appropriate timing. As a result, normal laser processing can be continued, and it is possible to reduce the loss of the processing object and the waste of processing time.

  According to another feature of the present invention, the switching period setting unit determines the interval between the irradiation position of the processing laser beam and the irradiation position of the inspection laser beam by rotating the rotating unit. A value obtained by dividing the irradiation speed by the linear velocity is set as a theoretical delay time, and a control mode switching period in which an end time later than the theoretical delay time is set is set from the end time of the abnormal period.

  The timing at which the processing laser light irradiates the abnormal portion is delayed with respect to the timing at which the inspection laser light irradiates the abnormal portion. This delay time is obtained by dividing the interval between the irradiation position of the processing laser beam and the irradiation position of the inspection laser beam by the linear velocity at which the irradiation position of the processing laser beam moves by the rotation of the rotating means. Therefore, in the present invention, this delay time is set as a theoretical delay time, and the end time of the control mode switching period is set to be delayed by at least the theoretical delay time from the end time of the abnormal period. Thus, the abnormality detection mode can be reliably continued until the irradiation position of the processing laser light passes through the abnormal portion. For this reason, it is possible to reliably prevent the focus servo from coming off.

  Further, the present invention is characterized in that the switching period setting means delays the start timing of the control mode switching period by a first delay time shorter than the theoretical delay time with respect to the start timing of the abnormal period. And a second delay means for delaying the end time of the control mode switching period by a second delay time longer than the theoretical delay time with respect to the end time of the abnormal period.

  As described above, the timing at which the processing laser light irradiates the abnormal portion is delayed by a certain time (theoretical delay time) with respect to the timing at which the inspection laser light irradiates the abnormal portion. Therefore, if the control mode switching period is delayed as a whole with respect to the abnormal period by this theoretical delay time, it is possible to prevent the focus servo from being lost, but if an error such as a control response delay is considered, the control mode switching period It is possible to reliably prevent the focus servo from being released by delaying the start timing of the control mode earlier than the timing delayed by the theoretical delay time and further delaying the end timing of the control mode switching period than the timing delayed by the theoretical delay time. Therefore, in the present invention, the first delay means delays the start time of the control mode switching period by a first delay time shorter than the theoretical delay time with respect to the start time of the abnormal period, and the second delay means controls the control mode. The end time of the switching period is delayed by a second delay time longer than the theoretical delay time with respect to the end time of the abnormal period. As a result, according to the present invention, the control mode can be switched at an appropriate timing, and the focus servo can be reliably prevented from coming off.

  Another feature of the present invention is that the control mode switching means holds the position of the objective lens by holding the drive signal for driving the objective lens so as not to change during the control mode switching period. There is to do.

  In the present invention, only during the control mode switching period, the control mode switching means holds so as not to change the drive signal for driving the objective lens. For example, by giving a pseudo focus error signal with zero focus deviation to the focus servo means, the drive signal for driving the objective lens is held so as not to be changed so that the objective lens is not driven in the optical axis direction. Can be. Therefore, during this period, the position of the objective lens is maintained regardless of the distance between the surface of the workpiece and the objective lens. For this reason, even if an abnormal portion exists on the surface of the workpiece, the objective lens is not driven in response thereto. When the irradiation position of the processing laser light exits from the abnormal part and the control mode switching period ends, the control mode switching means releases the hold of the drive signal. Accordingly, thereafter, the objective lens is driven by the focus servo means so that the focal position of the processing laser light coincides with the surface of the processing object based on the reflected light of the processing laser light from the processing object. The Therefore, laser processing can be continued without losing the focus servo. In addition, since the position of the objective lens is maintained without changing the drive signal for driving the objective lens, it can be implemented with a very simple configuration.

  Another feature of the present invention is that the focus servo means receives reflected light from the processing object of the processing laser light by a first light receiving optical system, and shifts a focal position from the received light signal. A focus error signal is generated, and the objective lens is driven in the optical axis direction of the processing laser beam so that the focal position of the processing laser beam coincides with the surface of the processing object based on the focus error signal The first focus servo system that receives the reflected light from the object to be processed of the processing laser light is received by the second light receiving optical system, and a focus error signal that indicates a deviation from the focal position is generated from the received light signal. The objective lens is driven in the optical axis direction of the processing laser beam so that the focal position of the processing laser beam coincides with the surface of the processing object based on the focus error signal. And a second focus servo system having a wider focus position deviation detection range than the first first servo system, the control mode switching means for the focus servo means with respect to the focus servo means. An instruction to operate the second focus servo system instead of the first focus servo system is output during the control mode switching period.

  In the present invention, the focus servo means includes a first focus servo system and a second focus servo system having a wider focal position control range than the first focus servo system. For example, when a signal generated by calculation using the astigmatism method is used as the focus error signal, the focus position control range becomes wider as the S-shaped detection distance is longer. On the other hand, the longer the S-shaped detection distance, the lower the followability to the surface displacement of the workpiece. Therefore, the first focus servo system can perform focus servo control with a good tracking ability although the focus position control range is narrow, and the second focus servo system is a focus with a wide focus position control range although the tracking ability is inferior Servo control can be performed.

  When an abnormal part is detected on the surface of the workpiece based on the intensity of the reflected light of the inspection laser light, the control mode switching period is set based on the abnormal period in which the abnormal part is detected. When the control mode switching period is set, the control mode switching means outputs an instruction to operate the second focus servo system instead of the first focus servo system during the control mode switching period. Thus, the focus servo means starts focus servo control using the second focus servo system. In this case, since the control range of the focal position is widened, the focus servo is unlikely to come off even when the processing laser light irradiates the abnormal part. Then, when the irradiation position of the processing laser light exits from the abnormal part and the control mode switching period ends, the focus servo means uses the first focus servo system instead of the second focus servo system, and the focus servo with good followability Start control. Therefore, good laser processing can be continued without losing the focus servo.

  Another feature of the present invention is that the set portion has a plurality of plate-shaped fixing jigs formed with a plurality of fixing circular holes for inserting and fixing a disk-shaped workpiece in the thickness direction. The processing object is arranged and fixed on the same plane, and the focus servo means applies the reflected light from the irradiation surface even when the processing laser light is not irradiating the processing object. Based on this, the objective lens is driven in the optical axis direction of the processing laser beam so that the focal position of the processing laser beam coincides with the irradiation surface, and the processing is inserted and fixed in the fixed circular hole. Boundary detection means for detecting the boundary between the outer periphery of the object and the fixed circular hole, and the processing laser light irradiates the surface of the fixing jig including the boundary based on the boundary detected by the boundary detection means. When you Against Susabo means, in that a workpiece non-irradiation control mode changeover means for outputting an instruction to actuate the second focus servo system.

  In the present invention, a plurality of disk-shaped workpieces are inserted and fixed in the fixed circular holes of the fixing jig and arranged on the same plane in the set portion. Therefore, when the set unit is rotated, the irradiation target of the processing laser beam and the inspection laser beam is switched between the processing target and the fixing jig in accordance with the rotation angle of the set unit. The focus servo means continues the focus servo control even when the processing laser light is not irradiating the object to be processed, that is, when the surface of the fixing jig is irradiated. If the height of the surface of the workpiece and the surface of the fixing jig do not match, a step is produced at the boundary between the two. Therefore, there is a possibility that the focus servo may come off due to this step.

  Therefore, in the present invention, the boundary between the outer periphery of the workpiece inserted and fixed in the fixed circular hole and the fixed circular hole is detected by the boundary detection means. This boundary detection may be performed in advance before performing laser processing. When the processing object non-irradiation control mode switching means irradiates the surface of the fixture including the boundary with the processing laser light based on the boundary detected by the boundary detection means during laser processing, the focus servo An instruction to operate the second focus servo system is output to the means. Therefore, even if there is a step between the surface of the workpiece and the surface of the fixing jig, focus servo control is performed by the second focus servo system having a wide control range of the focus position, so that the focus servo can be prevented from being detached. . Further, when the processing laser light passes the next boundary and irradiates the surface of the object to be processed, the focus servo control is switched to the first focus servo system, so that accurate laser processing can be performed.

  In addition, when there is an abnormal part on the surface of the workpiece by using this focus servo system switching, the focus servo is disconnected by the abnormal part because the first focus servo system is switched to the second focus servo system. Can also be prevented. As a result, laser processing can be continued at the same time without losing the focus servo for a plurality of processing objects, and the production efficiency can be further improved.

  Another feature of the present invention is that a cut-off frequency for cutting a high-frequency component of the focus error signal in the second focus servo system is a cut-off frequency for cutting a high-frequency component of the focus error signal in the first focus servo system. This is because it is set lower than the off-frequency.

  If the outer diameter of the workpiece does not match the inner diameter of the fixed circular hole of the fixing jig, a gap is generated at the boundary. For this reason, when the laser beam for processing irradiates the boundary, the focus error signal may fluctuate rapidly in response to the gap and the focus servo may be lost. The focus servo means has a low-pass filter function for cutting a high frequency component of the focus error signal. Therefore, by setting the cut-off frequency of the second focus servo system to be low, the focus servo control is sensitive even if the focus error signal fluctuates rapidly when the irradiation position of the processing laser beam passes the boundary. Can be made to not react. As a result, even if there is a gap at the boundary, it is possible to prevent the focus servo from coming off.

  Furthermore, in carrying out the present invention, the invention is not limited to the invention of the laser processing apparatus, but can also be implemented as an invention of a laser processing method.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic system configuration diagram of a laser processing apparatus 1 according to the first embodiment. The laser processing apparatus 1 includes a table 21 as a support member that fixes and supports the workpiece OB, and a machining head 30 that irradiates the workpiece OB with laser light and laser-processes the workpiece OB. ing. The object to be processed OB is a disk-shaped thin plate, and is finally laser-processed to be used as a functional material such as an antireflection film or a polarizing plate. The table 21 is formed in a disk shape and is driven by a spindle motor 22 and a feed motor 23. The processing head 30 is fixed by a head support frame (not shown) fixed to the apparatus main body.

  The spindle motor 22 rotationally drives the table 21 through the rotation shaft 22b by the rotation. The spindle motor 22 incorporates an encoder 22a that detects the rotation of the motor 22, that is, the table 21, and outputs a rotation detection signal representing the rotation. This rotation detection signal includes an index signal generated every time the rotation position of the table 21 reaches one reference rotation position, and a voltage level that is high and low each time the table 21 rotates by a predetermined minute rotation angle. The pulse train signals are alternately switched to each other and consist of an A-phase signal and a B-phase signal that are shifted in phase by π / 2. In the first embodiment, only the pulse train signal is used as the rotation detection signal.

  The rotation detection signal is supplied to the spindle motor control circuit 53. The spindle motor control circuit 53 starts to operate in response to a rotational speed instruction from the controller 90, and the rotational speed of the spindle motor 22 is determined by the number of pulses per unit time of the pulse train signals (A phase signal and B phase signal) output from the encoder 22a. And the rotation of the spindle motor 22 is controlled so that the calculated rotation speed becomes equal to the rotation speed instructed by the controller 90.

  The feed motor 23 rotates the screw rod 24 to drive the table 21 in the radial direction. The screw rod 24 is connected to one end of the screw rod 24 so as to rotate integrally with the rotation shaft of the feed motor 23, and is screwed to a nut (not shown) fixed to the support member 25 at the other end. The support member 25 fixedly supports the spindle motor 22 and is only allowed to move in the radial direction of the table 21. Therefore, when the feed motor 23 rotates, the spindle motor 22, the table 21, and the support member 25 are displaced in the radial direction of the table 21 by the feed screw mechanism 20 including the screw rod 24 and the nut. The movement direction of the table 21 is set so that a straight line representing the movement locus of the rotation center of the table 21 passes through the irradiation area of the machining head 30.

  Also incorporated in the feed motor 23 is an encoder 23a that detects the rotation of the feed motor 23 and outputs a rotation detection signal (pulse train signal composed of an A-phase signal and a B-phase signal) similar to the encoder 22a. The pulse train signal output from the encoder 23 a is output to the feed motor control circuit 54 and the radial position detection circuit 52. The radial position detection circuit 52 counts up or down the number of pulses of the pulse train signal from the encoder 23a in accordance with the rotation direction of the feed motor 23, and feeds the table 21 irradiated with laser light from the count value in the radial direction. A position (hereinafter referred to as a radial position) is detected, and a digital signal representing the radial position is output to the controller 90. The initial setting of the count value in the radial position detection circuit 52 is performed by an instruction from the controller 90 when the power is turned on.

  The feed motor control circuit 54 drives and controls the feed motor 23 according to an instruction from the controller 90 to move the irradiation position of the laser beam to a designated radial position of the table 21 or move the table 21 in the radial direction at a designated speed. . Specifically, the feed motor control circuit 54 feeds using the radial position detected by the radial position detection circuit 52 when the movement of the laser beam irradiation position to the radial position specified by the controller 90 is specified. The rotation of the motor 23 is controlled, and the feed motor 23 is rotated until the detected radial position becomes equal to the radial position designated by the controller 90. When the feed motor control circuit 54 is instructed to move the laser light irradiation position in the radial direction of the table 21 at the moving speed designated by the controller 90, the radius of the table 21 is determined from the rotation detection signal from the encoder 23a. The movement speed in the direction is calculated, and the rotation of the feed motor 23 is controlled so that the calculated movement speed becomes equal to the movement speed designated by the controller 90.

  Next, the processing head 30 will be described. The processing head 30 includes a first laser light source 31 and a second laser light source 41. The processing head 30 irradiates laser light emitted from the light sources 31 and 41 toward the processing object OB and receives the reflected light separately. It is the composition to do. The laser light emitted from the first laser light source 31 is mainly used for laser processing the workpiece OB, and the laser light emitted from the second laser light source 41 is weak that the workpiece OB cannot be laser processed. The strength is adjusted and used to detect an abnormal portion on the surface of the workpiece OB. Hereinafter, the laser light emitted from the first laser light source 31 is referred to as processing laser light, and the laser light emitted from the second laser light source 41 is referred to as inspection laser light. Note that the first laser light source 31 has a weak intensity (hereinafter referred to as non-processing intensity) at which the workpiece OB cannot be laser processed by adjusting a drive signal from a first laser drive circuit 71 described later when focus servo is started. ) Laser light can also be emitted. Only when laser light having non-processing intensity is emitted from the first laser light source 31, the laser light is referred to as non-processing laser light.

  The processing head 30 includes a first laser light source 31, a first collimating lens 32, a first polarizing beam splitter 33, a dichroic mirror 34, a quarter wavelength plate 35, an objective lens 36, a first condenser lens 37, a cylindrical lens 38, A first photodetector 39, a focus actuator 40, a second laser light source 41, a second collimator lens 42, a second polarizing beam splitter 43, a second condenser lens 44, a second photodetector 45, and the like are provided. The processing laser light emitted from the first laser light source 31 passes through the first collimating lens 32, the first polarizing beam splitter 33, the dichroic mirror 34, and the quarter wavelength plate 35, and passes through the object lens OB by the objective lens 36. Condensed on the surface. Further, the processing laser light condensed on the surface of the processing object OB is reflected by the surface of the processing object OB. The reflected light reflected from the surface of the workpiece OB is converted into parallel light by the objective lens 36, passes through the quarter-wave plate 35 and the dichroic mirror 34 as it is, enters the first polarization beam splitter 33, and enters the first polarization. The light is reflected by the beam splitter 33 and enters the first condenser lens 37. The first condensing lens 37 condenses the light reflected by the first polarizing beam splitter 33 on the first photodetector 39 via the cylindrical lens 38.

  The second laser light source 41 emits laser light having a wavelength different from that of the first laser light source 31. The inspection laser light emitted from the second laser light source 41 enters the dichroic mirror 34 via the second collimating lens 42 and the second polarizing beam splitter 43. The dichroic mirror 34 transmits the processing laser light emitted from the first laser light source 31 and the reflected light as it is, but reflects the inspection laser light emitted from the second laser light source 41. . The inspection laser light reflected by the dichroic mirror 34 passes through the quarter-wave plate 35 and the objective lens 36 and is condensed on the surface of the processing object OB. That is, the inspection laser light is combined with the processing laser light, passes through the quarter-wave plate 35, and is condensed on the surface of the processing object OB by the objective lens 36.

  In this case, the optical axis of the inspection laser reflected from the dichroic mirror 34 is opposite to the rotation direction of the workpiece OB with respect to the optical axis of the processing laser emitted from the first laser light source 31 and transmitted through the dichroic mirror 34. Slightly tilted in the direction. Accordingly, the inspection laser light emitted from the second laser light source 41 is rotated in the rotation direction of the processing object OB with respect to the spot position irradiated on the processing object OB by the processing laser light emitted from the first laser light source 31. Condensed at a position slightly apart in the opposite direction. In the present embodiment, for example, the separation of the condensing positions on the surface of the object to be processed of the two laser beams is set to about 50 μm. Hereinafter, the interval between the irradiation position of the processing laser beam (the center position of the light spot) and the irradiation position of the inspection laser beam (the center position of the light spot) on the surface of the workpiece is referred to as an irradiation position interval DS.

  The reflected light from the processing object OB of the inspection laser light becomes parallel light by the objective lens 36, passes through the ¼ wavelength plate 35, and is reflected by the dichroic mirror 34. Accordingly, the reflected light of the inspection laser light is separated from the reflected light of the processing laser light by the dichroic mirror 34. The reflected light reflected by the dichroic mirror 34 is reflected by the second polarizing beam splitter 43 and enters the second condenser lens 44. The second condenser lens 44 condenses the light reflected by the second polarization beam splitter 43 on the second photodetector 45. The second photodetector 45 outputs a signal corresponding to the intensity of the inspection laser beam reflected by the second polarization beam splitter 43.

  The first laser light source 31 is driven by a first laser drive circuit 71 that is controlled by the controller 90. The second laser light source 41 is driven by a second laser driving circuit 72 that is controlled by the controller 90. In the first laser drive circuit 71, the output form of the drive signal to the first laser light source 31 is controlled by the light emission signal supply circuit 73.

  The light emission signal supply circuit 73 inputs data representing a machining pattern from the controller 90 and supplies a pulse train signal or a continuous signal corresponding to the data to the first laser driving circuit 71 during laser machining. When the light emission signal supply circuit 73 forms a plurality of fine pits in a line on the surface of the workpiece OB, the high level signal and the low level having a time width corresponding to the length of the pits and the pit formation interval. When a pulse train signal composed of a signal is output and a continuous groove is formed on the surface of the workpiece OB, a continuous high level signal is output.

  The first laser drive circuit 71 supplies a current and a voltage for emitting laser light having a specified intensity to the first laser light source 31 based on a command from the controller 90. When the first laser driving circuit 71 receives a command to start laser irradiation with non-processing intensity from the controller 90, the first laser driving circuit 71 generates a driving signal composed of a DC signal at a low level (that is, non-processing level) in response to the first laser driving circuit 71. Output to the light source 31. This non-machining level is low enough that the surface of the workpiece OB is not changed by the irradiation of the laser beam emitted from the first laser light source 31 onto the surface of the workpiece OB (not laser-machined), and will be described later. The level is set to enable focus servo control.

  When the first laser drive circuit 71 receives a command for starting the laser irradiation of the processing intensity from the controller 90, the first laser drive circuit 71 responds to a high-level (ie, processing level) pulse train signal or a DC signal as a drive signal. Output to the first laser light source 31. The waveform of the high-level drive signal is set according to the signal input from the light emission signal supply circuit 73. For example, if the signal input from the light emission signal supply circuit 73 is a pulse train signal, the waveform according to the pulse signal waveform. It becomes. This processing level is a level at which the surface of the processing object OB is laser processed by irradiating the surface of the processing object OB with the laser light emitted from the first laser light source 31 and focus servo control described later is possible. Is set to

  The reflected light from the surface of the processing object OB of the processing laser light is guided to the first photodetector 39 and received. The first photodetector 39 is composed of four divided light receiving elements composed of four identical square light receiving elements separated by a dividing line, and light incident on the light receiving areas A, B, C, and D arranged in the clockwise direction. A detection signal having a magnitude proportional to the intensity of the light is output as a light reception signal (a, b, c, d). The first photodetector 39 is fixed so that the reflected light is collected at the center where the four light receiving elements are arranged.

  The received light signals (a, b, c, d) output from the first photodetector 39 are input to the first signal amplifier circuit 61. The first signal amplifier circuit 61 amplifies the received light signals (a, b, c, d) and outputs the amplified signals to the focus error signal generation circuit 62. The focus error signal generation circuit 62 generates a focus error signal by calculation using the amplified light reception signals (a ′, b ′, c ′, d ′). In this embodiment, since the focus servo control by the astigmatism method is used, the calculation of (a ′ + c ′) − (b ′ + d ′) is performed, and the conduction circuit 63 is set using the calculation result as a focus error signal. To the focus servo circuit 64. As shown in FIG. 16, the focus error signal (a ′ + c ′) − (b ′ + d ′) becomes an S-shaped waveform signal when the distance between the objective lens and the surface of the workpiece is changed. When the focal position of the workpiece OB coincides with the surface of the workpiece OB, a value of zero is taken (zero cross point P0 in the figure). It takes a value according to it. In this case, the absolute value of the focus error signal increases as the shift amount increases at a point close to the focal position. However, if the shift amount becomes too large, the absolute value of the focus error signal decreases. Accordingly, the range in which focus servo control is possible is within the S-shaped detection area between the peak points P1 and P2 shown in FIG.

  The continuity circuit 63 is provided between the focus error signal generation circuit 62 and the focus servo circuit 64, and during the period when a high level signal is input from a delay circuit 68 described later, a focus error is generated with respect to the focus servo circuit 64. As a pseudo signal, a zero level signal (a signal indicating zero focal position shift amount) is output. On the other hand, during a period when no high level signal is input from the delay circuit 68, the focus error signal input from the focus error signal generation circuit 62 is output to the focus servo circuit 64 as it is.

  The focus servo circuit 64 is controlled by the controller 90, generates a focus servo signal based on the focus error signal, and outputs the focus servo signal to the drive circuit 65. The drive circuit 65 drives the focus actuator 40 according to the focus servo signal to displace the objective lens 36 in the optical axis direction of the laser light. When the objective lens 36 is displaced, the focus error signal (a ′ + c ′) − (b ′ + d ′) changes to an S shape in the vicinity where the focal position of the laser beam coincides with the surface of the workpiece OB. In the focus servo circuit 64, the value of the focus error signal (a ′ + c ′) − (b ′ + d ′) becomes a constant value (zero) at a timing near the middle of the range in which the focus servo signal changes in an S shape. Thus, by supplying the focus servo signal to the drive circuit 65, the laser beam can be continuously focused on the surface of the workpiece OB.

  The second laser drive circuit 72 outputs, to the second laser light source 41, a drive signal composed of a DC signal at the inspection level, with respect to the second laser light source 41, based on a command from the controller 90. This inspection level is so weak that the surface of the workpiece OB is not changed (not laser-processed) by irradiation of the laser beam (inspection laser beam) emitted from the second laser light source 41 onto the surface of the workpiece OB. It is set.

  The reflected light from the surface of the workpiece OB of the inspection laser light is guided to the second photodetector 45 and received. The second photodetector 45 outputs a detection signal having a magnitude proportional to the intensity of the incident light as a light reception signal. That is, a received light signal having a larger peak value is output as the intensity of received light increases. The light reception signal output from the second photodetector 45 is input to the second signal amplifier circuit 66. The second signal amplification circuit 66 amplifies the received light reception signal to an appropriate signal level and outputs it to the mask signal generation circuit 67. Hereinafter, the light reception signal amplified by the second signal amplification circuit 66 is simply referred to as a light reception signal.

  The mask signal generation circuit 67 starts to operate when receiving an instruction from the controller 90. The mask signal generation circuit 67 has two reference levels, a first reference level R1 for comparison with the signal level (peak value) of the received light reception signal and a second reference level R2 higher than the first reference level R1. It is a set comparator. These two reference levels R1 and R2 correspond to the reference intensity of the present invention, and the normal value that can be taken by the peak value of the received light signal obtained when the surface of the normal workpiece OB is irradiated with the inspection laser light. A range is set. Therefore, when the peak value of the received light signal is lower than the first reference level R1 or higher than the second reference level R2, foreign matter adheres to the surface of the processing object OB at the position where the inspection laser beam is irradiated. It can be considered that there is an abnormal part such as a scratch. If the surface of the workpiece OB is in a state where the peak value of the received light signal is within the normal range (a state in which no abnormal portion exists), the focus servo by the focus servo circuit 64 described above will not be lost.

  The mask signal generation circuit 67 outputs a low level signal to the delay circuit 68 when the peak value of the light reception signal takes a value in a normal range that is equal to or higher than the first reference level R1 and equal to or lower than the second reference level R2. When the peak value of the signal is lower than the first reference level R1 or when the value of the abnormal range is higher than the second reference level R2, a high level signal is output to the delay circuit 68. Hereinafter, a signal output from the mask signal generation circuit 67 is referred to as a mask signal. In general, when an abnormal part is present on the surface of the workpiece OB, the intensity of the reflected light is reduced, but in some rare cases, the intensity of the reflected light is increased. Therefore, in the present embodiment, the presence or absence of an abnormal portion is determined by providing two reference levels R1 and R2 that are high and low, but determination based on one reference level, that is, when the intensity of reflected light falls below the reference level R1. It may be configured to output a high level signal by determining that an abnormal portion exists only in

  Here, the transition of the peak value of the received light signal and the mask signal that changes along with this will be described with reference to FIG. As shown in FIG. 3, while the peak value of the received light signal is between the first reference level R1 and the second reference level R2, the mask signal maintains a low level. When the light spot of the inspection laser light enters the abnormal part of the object OB, the peak value of the received light signal decreases. When the peak value of the received light signal falls below the first reference level R1 (time t1), the mask signal switches from the low level to the high level. Thereafter, when the light spot of the inspection laser light exits from the abnormal portion, the peak value of the light reception signal increases. When the peak value of the received light signal becomes equal to or higher than the first reference level R1 (time t2), the mask signal is switched to the low level again and maintains that state.

As shown in FIG. 2, the delay circuit 68 includes a first delay circuit 681, a second delay circuit 682, and a flip-flop circuit 683. The first delay circuit 681 and the second delay circuit 682 receive the mask signal output from the mask signal generation circuit 67. The first delay circuit 681 receives a signal representing the delay amount d1 from the controller 90, and outputs a first delay signal obtained by delaying the mask signal by the delay amount d1. The second delay circuit 682 receives a signal representing the delay amount d2 (> d1) from the controller 90, and outputs a second delay signal obtained by delaying the mask signal by the delay amount d2. The delay amounts d1 and d2 are calculated by the controller 90 as follows.
d1 = (DS / v) −A (1)
d2 = (DS / v) + A (2)
Here, DS represents the interval (irradiation position interval) between the irradiation position of the processing laser beam and the irradiation position of the inspection laser beam on the surface of the processing object OB, and v represents the processing laser by the rotation of the table 21. The light irradiation position is a linear velocity at which the surface of the workpiece OB moves, and A is a positive fine value set in advance.

  The flip-flop circuit 683 receives the output signal of the first delay circuit 681 and the output signal of the second delay circuit 682, and uses the output signal as the rising edge of the first delay signal (when switching from low level to high level). Is switched from the low level to the high level, and switched from the high level to the low level at the fall of the second delay signal (when switching from the high level to the low level). The output signal of the flip-flop circuit 683 is output to the conduction circuit 63 and used as a signal for holding the focus servo.

  The continuity circuit 63 receives the output signal of the flip-flop circuit 683, and when the output signal is at a high level, the continuity circuit 63 outputs a zero level signal (focus position signal) as a pseudo error signal to the focus servo circuit 64. A signal indicating zero deviation) is output. Accordingly, during the period when the output signal of the flip-flop circuit 683 is at a high level, the focus error signal is maintained at a zero level signal, so that the focus servo circuit 64 has a constant intensity with respect to the drive circuit 65. A servo signal is output, and the drive circuit 65 outputs a drive signal having a constant strength to the focus actuator 40. Therefore, the objective lens 36 is held at the same position (position immediately before the output of the flip-flop circuit 683 becomes high level) and does not move. That is, the focus servo is held. As described above, since the output signal of the flip-flop circuit 683 is used for holding the focus servo, the output signal is hereinafter referred to as a hold signal.

  Here, the timing of holding the focus servo will be described with reference to FIG. When the light spot of the inspection laser beam enters the abnormal part of the workpiece OB, the peak value of the received light signal decreases and falls below the first reference level R1 (time t1). When exiting from the abnormal part, the peak value of the received light signal increases and returns to the first reference level R1 or higher (time t2). Therefore, the mask signal maintains a high level from time t1 to time t2. The first delay circuit 681 outputs a first delay signal obtained by delaying the mask signal by the delay amount d1. That is, a high level signal is output from time t3 (= t1 + d1) to time t5 (= t2 + d1). On the other hand, the second delay circuit 682 outputs a second delay signal obtained by delaying the mask signal by the delay amount d2. That is, a high level signal is output from time 4 (= t1 + d2) to time t6 (t2 + d2).

  The flip-flop circuit 683 outputs a high level signal during the period from the rising edge of the first delay signal to the falling edge of the second delay signal, that is, from time t3 to time t6. Accordingly, the focus servo is held only from time t3 to time t6.

  In the laser processing apparatus 1 according to the present embodiment, as will be described later, the table 21 on which the processing object OB is set is fed and moved in the radial direction while rotating from the first laser light source 31 of the processing head 30. The surface of the processing object OB is laser processed by irradiating the processing laser beam. At the same time, the inspection laser beam is irradiated to a position immediately before the processing laser beam is irradiated. During laser processing, when the intensity of the reflected light of the inspection laser beam is out of the normal range, a high level mask signal is output from the mask signal generation circuit 67. Therefore, when the mask signal is at a high level, the inspection laser light is irradiating the abnormal portion. The irradiation position of the inspection laser beam is a position shifted in the processing direction by the irradiation position interval DS with respect to the irradiation position of the processing laser beam. Therefore, before the processing laser beam irradiates the abnormal part, the presence of the abnormal part can be detected in advance and the focus servo can be held.

  A waveform indicated by a broken line in FIG. 3 represents a peak value when the intensity of the reflected light is detected at the irradiation position of the processing laser light. This example is an example in which a processing laser beam having a certain intensity is irradiated (groove processing is performed). The delay time of this waveform with respect to the received light signal waveform input to the mask signal generation circuit 67 can be expressed as DS / v. Therefore, if the focus servo is held before this delay time (DS / v) has elapsed from time t1, the focus servo will not be lost. Therefore, in the present embodiment, as shown in the above-described equation (1), the hold signal is at the high level first by a minute value (minute time) A before the time when the delay time (DS / v) elapses from time t1. Is set to switch to. Further, the focus servo hold needs to be continued until the light spot of the processing laser light comes out of the abnormal portion. Therefore, in the present embodiment, as shown in the above-described equation (2), the hold signal is set to a low level with a delay of a minute value (minor time) A further from the time when the delay time (DS / v) has elapsed from time t2. It is set to switch. Therefore, during the period when the peak value of the reflected light indicated by the broken line in FIG. 3 is lower than the first reference level R1, the hold signal is surely at the high level. As a result, the focus servo hold start and hold release timings can be set appropriately, and the focus servo can be prevented from coming off due to an abnormal portion.

  Next, the operation of the laser processing apparatus 1 will be described. The operator turns on a power switch (not shown) of the laser processing apparatus 1 to start operation of various circuits shown in FIG. When the power is turned on, the controller 90 instructs the radial position detection circuit 52 and the feed motor control circuit 54 to perform initial settings by executing a program (not shown). In response to this instruction, the feed motor control circuit 54 rotates the feed motor 23 to move the table 21 to the initial position which is the drive limit position. When the table 21 reaches the initial position and the rotation of the feed motor 23 stops, the radial position detection circuit 52 detects the stop of the input of the pulse train signal from the encoder 23a, resets the count value to “0”, and controls the feed motor. A signal for stopping output is output to the circuit 54 to complete the initial setting.

  Next, the controller 90 prompts the operator to input machining data necessary for machining the workpiece OB using the display device 92 by executing a program (not shown). The operator uses the input device 91 to specify the laser processing start radius position, the laser processing end radius position, the processing pitch in the radial direction, the rotational linear velocity of the laser spot with respect to the processing object OB, the designation of grooving or pit processing, and pits. In the case of machining, the pit interval in the rotation direction is input. The controller 90 stores the input machining data in an internal storage device. Note that this processing may be omitted when the machining data is stored in the controller 90.

  After execution of such initial processing, a laser processing routine is started. FIG. 4 is a flowchart showing a laser processing routine. This laser processing routine is stored as a control program in the ROM of the controller 90, and is started in step S10. First, in step S12, the controller 90 instructs the feed motor control circuit 54 to move to the input laser processing start radius position. The feed motor control circuit 54 controls the rotation of the feed motor 23 until the irradiation position of the laser beam coincides with the laser processing start radial position while inputting the radial position detected by the radial position detection circuit 52. To move.

  Subsequently, the controller 90 calculates the rotation speed of the spindle motor 22 using the input laser processing start radius position and rotation linear velocity in step S14, and sends the calculated rotation speed to the spindle motor control circuit 53. Outputs and instructs the spindle motor 22 to start rotating. The spindle motor control circuit 53 calculates the rotational speed of the spindle motor 22 using the A-phase signal and the B-phase signal from the encoder 22a, so that the calculated rotational speed becomes equal to the rotational speed input from the controller 90. The rotation control of the spindle motor 22 is started. After outputting the rotation start instruction, the controller 90 repeats the calculation of the rotation speed of the spindle motor 22 by an interrupt routine different from this routine, and the calculated rotation speed is sent to the spindle motor control circuit 53 each time. Output.

  Subsequently, the controller 90 instructs the first laser driving circuit 71 to start irradiation of non-processing laser light in step S16. As a result, the first laser drive circuit 71 starts to output a non-machining level drive signal to the first laser light source 31. The first laser light source 31 emits non-processing laser light by this drive signal. In this way, a light spot of non-machining laser light is formed on the surface of the processing object OB, and the reflected light of this light spot is detected by the first photodetector 39. In this case, the processing object OB is not processed by the irradiation of the non-processing laser beam.

  Subsequently, in step S18, the controller 90 instructs the second laser driving circuit 72 to start irradiation of the inspection laser light. As a result, the second laser driving circuit 72 starts to output a driving signal having a constant inspection level to the second laser light source 41. The second laser light source 41 emits an inspection laser beam by this drive signal. In this way, a light spot of the inspection laser light is formed on the surface of the processing object OB at a position separated from the light spot of the non-processing laser light by the irradiation position interval DS, and the reflected light of this light spot is reflected by the second photodetector 45. Detected by. In this case, the processing object OB is not processed by the irradiation of the inspection laser beam.

  Subsequently, the controller 90 instructs the mask signal generation circuit 67 and the delay circuit 68 to start operation in step S20. In this case, the controller 90 calculates the delay amounts d1 and d2 using the above-described equations (1) and (2), and outputs the calculated values to the first delay circuit 681 and the second delay circuit 682.

  Subsequently, in step S22, the controller 90 instructs the focus servo circuit 64, a circuit that drives the focus actuator 40 (not shown), and an S-shaped detection circuit to start operation. Accordingly, the focus servo circuit 64 starts to operate at a timing near the middle of the S-shaped signal waveform shown in FIG. 16, and the objective lens is set so that the focal position of the non-machining laser beam always coincides with the surface of the workpiece OB. Control for displacing the position 36 in the optical axis direction is started. Subsequently, in step S24, the controller 90 instructs the first laser driving circuit 71 to start irradiation of the processing laser light and instructs the light emission signal supply circuit 73 to output a signal. Thereby, the first laser driving circuit 71 switches the driving signal output to the first laser light source 31 from the non-processing level to the processing level, and a waveform corresponding to the waveform of the signal supplied from the light emission signal supply circuit 73. To. Thus, the first laser light source 31 emits the processing laser light corresponding to the processing level. Accordingly, the processing object OB is irradiated with the processing laser light, and laser processing of the processing object OB is started.

  Subsequently, in step S26, the controller 90 instructs the feed motor control circuit 54 to start moving in the radial direction. In this case, the controller 90 calculates the moving speed based on the input rotational linear speed and processing pitch, and the radial position taken in from the radial position detecting circuit 52, and instructs the moving speed to the feed motor control circuit 54. . The feed motor control circuit 54 calculates the moving speed in the radial direction of the feed motor 23 using the A phase signal and the B phase signal from the encoder 23a, and the calculated moving speed is equal to the moving speed instructed from the controller 90. Thus, the rotation of the feed motor 23 is controlled. As a result, the table 21 starts moving in the radial direction at the instructed moving speed. The controller 90 repeats the calculation of the moving speed of the table 21 by an interrupt routine different from this routine after instructing the start of moving in the radial direction, and each time the calculated moving speed is fed to the feed motor control circuit. To 54.

  Thus, the relative position between the processing object OB and the processing head 30 is changed by the rotation of the table 21 and the movement in the radial direction, and the irradiation position of the processing laser light and the inspection laser light is the surface of the processing object OB. Move in a spiral. Accordingly, laser processing is performed on the surface of the processing object OB along the irradiation path of the processing laser light, and at the same time, the surface of the processing object OB immediately before laser processing is irradiated with the inspection laser light.

  Subsequently, the controller 90 takes in the radial position data output from the radial position detection circuit 52 in step S28, and determines in step S30 whether or not the processing end radial position has been reached. The processing end radius position is a value input and set by the operator at the start of laser processing. The processes in steps S28 and S30 are repeated until the radius position detected by the radius position detection circuit 52 matches the machining end radius position. Therefore, during this time, laser processing of the processing object OB by the processing laser light irradiation is continued. At the same time, an abnormal portion is detected based on the reflected light intensity of the inspection laser beam at the position immediately before laser processing. When an abnormal portion is detected, the mask signal is output from the mask signal generation circuit 67 to the delay circuit 68 only during the detection period, and the delay circuit 68 creates a hold signal based on the mask signal. With this hold signal, the focus servo is held during the period in which the processing laser light is irradiating the abnormal portion.

  When the radius position detected by the radius position detection circuit 52 reaches the machining end radius position (S30: Yes), the controller 90 instructs the focus servo circuit 64 to stop the operation in step S32, and the focus servo circuit 64 Stop focus servo control. Next, in step S34, the controller 90 instructs the second laser drive circuit 72 to stop irradiating the inspection laser light, and in step S36, the first laser drive circuit 71 is irradiated with the processing laser light. Instruct to stop. Thereby, irradiation of the inspection laser beam and the processing laser beam is stopped. Subsequently, the controller 90 instructs the mask signal generation circuit 67 and the delay circuit 68 to stop the operation in step S38.

  Subsequently, the controller 90 instructs the spindle motor control circuit 53 to stop the rotation in step S40, and instructs the feed motor control circuit 54 to stop moving in the radial direction in step S42. Thereby, the spindle motor 22 and the feed motor 23 are stopped. When the rotation of the table 21 and the movement in the radial direction are stopped in this way, the laser processing routine is finished in step S44.

  According to the laser processing apparatus 1 of the first embodiment described above, the inspection laser light is irradiated to the front position in the processing direction of the light spot of the processing laser light, and the position immediately before the laser processing is based on the intensity of the reflected light. An abnormal part is detected. When an abnormal part is detected, a hold signal is created in consideration of a time delay until the processing laser light irradiates the abnormal part. That is, the hold signal is set to the high level immediately before the light spot of the processing laser light enters the abnormal portion, and the hold signal is returned to the low level immediately after the light spot exits the abnormal portion. As a result, during the period when the processing laser light is irradiating the abnormal portion, the hold signal is maintained at a high level, and the conduction circuit 63 outputs the focus error signal to the focus servo circuit 64 as zero. Accordingly, the focus servo is held during this period. When the light spot of the processing laser light exits from the abnormal part, the hold signal returns to the low level, and the conduction circuit 63 outputs the focus error signal generated by the focus error signal generation circuit 62 to the focus servo circuit 64 as it is. Then, the focus servo hold is released. As a result, normal laser processing can be continued even if there is an abnormal portion on the surface of the processing object OB, and loss of the processing object OB and waste of processing time can be reduced.

  The period during which the mask signal is at the high level corresponds to the abnormal period of the present invention, and the period during which the hold signal is at the high level corresponds to the control mode switching period of the present invention. The control mode in which the focus error signal is set to the zero level signal and the focus servo is held corresponds to the abnormality detection mode of the present invention, and the focus error signal generated by the focus error generation circuit 62 is output to the focus servo circuit 64. The control mode for performing the focus servo control corresponds to the normal mode of the present invention.

  Next, the laser processing apparatus of 2nd Embodiment is demonstrated. In the first embodiment described above, a configuration is adopted in which the focus servo is held when an abnormal portion is detected at a position immediately before laser processing. However, in the second embodiment, two focus points having different control ranges of the focus position are used. A servo system, that is, two focus servo systems having different S-shaped detection distances, and a configuration in which the focus servo system is switched during laser processing is adopted. Moreover, in 1st Embodiment, although the laser processing apparatus which sets the one process target OB to the table 21 and laser-processes was demonstrated, the laser processing apparatus of 2nd Embodiment has several process object in the table 21. FIG. A configuration in which an object OB is set and laser processing is simultaneously performed on a plurality of workpieces OB is employed. FIG. 5 is a schematic configuration diagram of the laser processing apparatus 2 as the second embodiment, FIG. 6 is an explanatory diagram showing a method of setting the processing object OB on the table 21, and FIG. It is a schematic perspective view showing the state set to. Hereinafter, configurations different from those of the first embodiment will be described, and the same configurations as those of the first embodiment will be denoted by the same reference numerals as those of the first embodiment and description thereof will be omitted.

  In the laser processing apparatus 2 of the second embodiment, a plurality of processing objects OB are set on the table 21 via the fixing jig 110. As shown in FIG. 6, the fixing jig 110 is thin with a fixed circular hole 110 h for fixing a plurality of workpieces OB around the rotation axis of the table 21 (four in this embodiment). It is a disk and is placed on the upper surface of the table 21. The fixed circular holes 110h are arranged at equal intervals (90 degrees) in the circumferential direction at positions where the centers (circular centers) are separated from the center of the fixing jig 110 by a radius rc. All the processing objects OB have the same shape, and are fixed to the fixing jig 110 on the same plane by being inserted into the fixing circular holes 110h in the thickness direction. The thickness of the fixing jig 110 is formed substantially the same as the thickness of the workpiece OB.

  A plurality of suction holes 21 a are formed on the upper surface of the table 21, and a negative pressure is generated in the suction holes 21 a by operating a suction device (not shown) so that the fixing jig 110 and the workpiece OB are placed on the upper surface of the table 21. Secure with suction. The fixing jig 110 is positioned with respect to the table 21 by a guide (not shown) so that the center of the fixing jig 110 coincides with the center of the table 21.

  The laser processing apparatus 2 according to the second embodiment includes a rotation angle detection circuit 55 for detecting the rotation angle of the table 21. The rotation angle detection circuit 55 starts operating in response to an instruction from the controller 90, counts the number of pulses of the pulse train signal output from the encoder 22a, and calculates the rotation angle of the table 21 from the count value. When calculating the rotation angle of the table 21, the rotation angle detection circuit 55 clears the count value of the number of pulses to zero when the index signal is input from the encoder 22a, that is, sets the rotation angle of the table 21 to 0 °. Then, the rotation angle (rotation angle position) of the table 21 based on the rotation angle of 0 ° is calculated from the count value of the pulse train signal after the index signal is input. The rotation angle detection circuit 55 repeats the calculation of the rotation angle at a predetermined short cycle, and outputs a digital signal representing the calculated rotation angle to the switching signal generation circuit 56 and the controller 90 described later each time.

  Next, the processing head 300 will be described. The machining head 300 in the second embodiment is obtained by adding a beam splitter 46, a third condenser lens 47, a second cylindrical lens 48, and a third photodetector 49 to the machining head 30 in the first embodiment. The beam splitter 46 is provided between the first polarizing beam splitter 33 and the dichroic mirror 34. Most of the processing laser light emitted from the first laser light source 31 and converted into parallel light by the first collimating lens 32 is transmitted through the first polarizing beam splitter 33, and approximately half is transmitted through the beam splitter 46. The processing laser light that has passed through the beam splitter 46 passes through the dichroic mirror 34, becomes circularly polarized light by the quarter-wave plate 35, and is condensed by the objective lens 36, and is processed by the object OB or the fixing jig 110. Is irradiated. The reflected light reflected from the surface of the workpiece OB or the fixing jig 110 is converted into parallel light by the objective lens 36, the polarization direction is changed by 90 degrees by the quarter wavelength plate 35, and the light is transmitted through the dichroic mirror 34 as it is. The light enters the splitter 46.

  About half of the reflected light incident on the beam splitter 46 is transmitted, and the remaining half is reflected. The laser light that has entered and passed through the beam splitter 46 is incident on the first polarizing beam splitter 33 and most of it is reflected. The reflected light reflected by the first polarizing beam splitter 33 is condensed on the first photodetector 39 via the first condenser lens 37 and the cylindrical lens 38. Hereinafter, the first condenser lens 37, the cylindrical lens 38, and the first photodetector 39 are collectively referred to as a first light receiving optical system.

  A third condenser lens 47, a second cylindrical lens 48, and a third photodetector 49 are provided in the reflection direction of the beam splitter 46. The reflected light reflected by the beam splitter 46 is reflected by the third condenser lens 47, The light is condensed on the third photodetector 49 through the two cylindrical lens 48. Similar to the first photodetector 39, the third photodetector 49 is composed of four divided light receiving elements composed of four light receiving elements of the same square shape separated by dividing lines, and the light receiving regions A, A detection signal having a magnitude proportional to the intensity of light incident on B, C, and D is output as a light reception signal (a, b, c, d). Hereinafter, the third condenser lens 47, the second cylindrical lens 48, and the third photodetector 49 are collectively referred to as a second light receiving optical system.

  The S-shaped detection distance in the first (second) light receiving optical system can be adjusted by the arrangement of the condenser lens 37 (47) and the cylindrical lens 38 (48). In the first light receiving optical system, an S-shaped detection distance as short as that of a general optical disc apparatus is set, and in the second light receiving optical system, an S-shaped detection distance longer than that in the first light receiving optical system is set. Has been. Therefore, the first light receiving optical system with a short S-shaped detection distance is suitable for performing focus servo with good followability and high accuracy, and the second light receiving optical system with a long S-shaped detection distance is suitable for following. Is inferior, but is suitable for focus servo within a controllable range of a wide focal position.

  By the way, the fixing jig 110 is formed so that the thickness thereof is the same as the thickness of the workpiece OB, but actually, as shown in FIG. 8, the processing surface of the workpiece OB and the fixing jig are fixed. A step Δt exists between the surface of the tool 110 (the surface that does not contact the table 21). If this step Δt is so large that it exceeds the controllable range of the focal position of the processing laser beam, the focus servo will be lost. At the time of laser processing, similarly to the first embodiment, the processing object OB is irradiated by irradiating the processing laser light from the first laser light source 31 while the table 21 is rotated and moved in the radial direction. Laser processing of the surface. Accordingly, the processing laser light is periodically irradiated to the surface of the fixing jig 110, and at the same time, focus servo control is performed.

  In order to perform laser processing of the processing object OB with high accuracy, it is necessary to perform focus servo control by shortening the S-shaped detection distance so that the focal position of the processing laser light follows the surface of the processing object OB satisfactorily. There is. In this case, the intermediate position of the peak points (P1, P2) of the S-shaped waveform signal obtained from the focus error signal is used as a reference, and the objective lens 36 is moved by an optical axis of the laser beam by the focus actuator 40 by a distance deviating from the intermediate position. Driven in the direction. Such focus servo control is possible in the range where the S-shaped waveform signal can be obtained from the focus error signal, that is, in the S-shaped detection area shown in FIG. Therefore, when the irradiation position of the processing laser light moves from the processing object OB to the fixing jig 110, the focus error signal may be outside the S-shaped detection area and the focus servo may be lost due to the influence of the step Δt.

  Therefore, the second embodiment includes a first focus servo system circuit 81 connected to the first light receiving optical system and a second focus servo system circuit 82 connected to the second light receiving optical system. By switching between the two focus servo system circuits 81 and 82, the focus servo is prevented from coming off. The first focus servo system circuit 81 is amplified by a signal amplification circuit 81a that amplifies a light reception signal (a, b, c, d) output from the first photodetector 39 of the first light reception optical system, and a signal amplification circuit 81a. The calculation (a ′ + c ′) − (b ′ + d ′), which is the calculation by the astigmatism method, is performed from the signals (a ′, b ′, c ′, d ′), and the calculation result is generated as a focus error signal. A focus error signal generation circuit 81b and a focus servo circuit 81c that generates a focus servo signal based on the focus error signal are provided. Hereinafter, the first focus servo system circuit 81 and the first light receiving optical system are collectively referred to as a first focus servo system.

  The second focus servo system circuit 82 includes a signal amplification circuit 82a that amplifies the light reception signals (a, b, c, d) output from the third photodetector 49 of the second light reception optical system, and a signal amplification circuit 82a. Calculation of the astigmatism method (a ′ + c ′) − (b ′ + d ′) is performed from the amplified signal (a ′, b ′, c ′, d ′), and the calculation result is used as a focus error signal. A focus error signal generation circuit 82b to be generated and a focus servo circuit 82c to generate a focus servo signal based on the focus error signal are provided. Hereinafter, the second focus servo system circuit 82 and the second light receiving optical system are collectively referred to as a second focus servo system.

  The focus servo circuits 81 c and 82 c each output a focus servo signal to the signal switching circuit 83. When the first signal is input from the switching signal generation circuit 56 or the error detection circuit 76 described later, the signal switching circuit 83 connects the focus servo circuit 81c of the first focus servo system and the drive circuit 65 to connect the focus servo. When the focus servo signal output from the circuit 81c is output to the drive circuit 65 and the second signal is input from the switching signal generation circuit 56 or the error detection circuit 76, the focus servo circuit 82c of the second focus servo system The drive circuit 65 is connected to a state where the focus servo signal output from the focus servo circuit 82 c is output to the drive circuit 65. The drive circuit 65 drives and controls the focus actuator 40 in accordance with the focus servo signal input via the signal switching circuit 83 to displace the objective lens 36 in the optical axis direction of the laser light. When the laser processing apparatus 2 is activated, the signal switching circuit 83 receives the second signal from the controller 90 and connects the focus servo circuit 82c of the second focus servo system and the drive circuit 65 to connect the focus servo circuit. The focus servo signal input from 82 c is set in a state of being output to the drive circuit 65.

  As described above, the S-shaped detection distance is set short in the first light receiving optical system, and the S-shaped detection distance is set long in the second light receiving optical system. Accordingly, when laser processing is performed by irradiating the surface of the processing object OB with the processing laser beam, the first focus servo system is used to perform focus servo control with good followability, and the processing laser beam is fixed to the fixture. When irradiating the surface of 110 and the boundary between the workpiece OB and the fixing jig 110, it is preferable to perform focus servo control using the second focus servo system so that the focus servo does not come off.

  Therefore, in the second embodiment, based on the rotation angle of the table 21, the case where the processing laser light irradiates the surface of the processing object OB, the surface of the fixing jig 110, and the processing object OB. And a switching signal generation circuit 56 for switching between two focus servo systems depending on whether the boundary between the fixing jig 110 and the fixing jig 110 is irradiated. The switching signal generation circuit 56 inputs the rotation angle of the table 21 output from the rotation angle detection circuit 55 and the radial position of the table 21 output from the radial position detection circuit during laser processing, and the fixing jig 110. This is an arithmetic circuit that switches the focus servo system based on the positional relationship between the processing object OB set on the laser beam and the irradiation position of the processing laser beam, and includes a microcomputer as a main part. The switching signal generation circuit 56 outputs a first signal after the irradiation position of the processing laser light has moved from the fixing jig 110 to the processing object OB, and the irradiation position of the processing laser light is fixed from the processing object OB. The second signal is output before moving to the tool 110. Details of the operation of the switching signal generation circuit 56 will be described later.

  The workpiece OB is inserted and fixed in the fixed circular hole 110h of the fixing jig 110. As shown in FIG. 8, the gap Δx is formed between the outer peripheral surface of the workpiece OB and the inner peripheral surface of the fixed circular hole 110h. May occur. When this gap Δx exists, the focus error signal is disturbed when the light spot of the processing laser beam passes through the boundary between the processing object OB and the fixing jig 110. For this reason, the focus position of the processing laser beam is controlled based on the disturbance of the focus error signal, and the focus servo may be lost. Each of the focus servo circuits 81b and 82b has a low-pass filter function that cuts high-frequency components of the input focus error signal, and is set so as not to react to disturbance by lowering the cutoff frequency of the low-pass filter. it can.

Therefore, in the second embodiment, the cutoff frequency of the focus servo circuit 82c in the second focus servo system is set lower than the cutoff frequency of the focus servo circuit 81c in the first focus servo system. For example, the cutoff frequency fc of the focus servo circuit 82c in the second focus servo system is set to be equivalent to 1/2 to 1/15 of the frequency of the signal component generated by the gap Δx. This relational expression (the expression when it is set to 1 / 2.5) is shown below.
fc = v [m / s] / (2.5 × Δx [μm]) × 10 ³ [kHz]
Here, v is a linear velocity at which the irradiation position of the processing laser light moves on the surface of the processing object OB by the rotation of the table 21.

  Thus, by lowering the cutoff frequency of the focus servo circuit 82c in the second focus servo system 82, the gap Δx exists between the workpiece OB and the fixed circular hole 110h, and the focus error signal is disturbed. However, since the focus servo circuit 82c generates a servo signal ignoring the disturbance, the focus servo cannot be removed.

  Next, a detection circuit for the reflected light of the inspection laser light will be described. The reflected light from the processing object OB or the surface of the fixing jig 110 of the inspection laser light is guided to the second photodetector 45 and received. The second photodetector 45 outputs a received light signal that has a higher peak value as the intensity of the incident light increases. The light reception signal output from the second photodetector 45 is input to the second signal amplifier circuit 66 and amplified to an appropriate signal level. The light reception signal amplified by the second signal amplification circuit 66 (simply referred to as a light reception signal) is input to the edge detection circuit 75 and the error detection circuit 76, respectively.

  The edge detection circuit 75 receives the light reception signal output from the second signal amplification circuit 66, and outputs an edge detection signal to the controller 90 when the peak value of the light reception signal crosses a preset value for edge detection. To do. That is, the edge detection circuit 75 compares the peak value of the received light signal with the edge detection setting value, and increases from the state where the peak value of the received light signal is lower than the edge detection setting value, and sets the edge detection setting value. When the value exceeds the set value for edge detection when the peak value of the received light signal exceeds the set value for edge detection and falls below the set value for edge detection, one pulse signal having a predetermined width is used as the edge detection signal. Output to the controller 90.

  The light reflectance of the surface of the processing object OB and the surface of the fixing jig 110 are different, and in this embodiment, the surface of the fixing jig 110 has a higher light reflectance than the surface of the processing object OB. . For this reason, when the table 21 is rotated in a state where the inspection laser beam is emitted from the second laser light source 41, the peak value of the received light signal output from the second signal amplification circuit 66 is changed to the edge portion of the workpiece OB. It changes at (outer periphery). Therefore, an inspection laser is set by previously setting an intermediate value between the peak value of the reflected light on the surface of the fixing jig 110 and the peak value of the reflected light on the surface of the workpiece OB as an edge detection setting value. When the light spot of light passes through the edge of the workpiece OB, the edge detection signal can be reliably output. This edge detection is also detection of the boundary between the outer periphery of the workpiece OB and the fixed circular hole 110h.

  In order for the switching signal generation circuit 56 described above to switch between the two focus servo systems, it is necessary to know in advance the set position of the workpiece OB with respect to the table 21. Therefore, by detecting the edge of the processing object OB by the edge detection circuit 75, the set position of the processing object OB can be grasped. FIG. 9 shows an arrangement of the processing object OB set on the fixing jig 110. Each processing object OB is disposed on the same circumference around the rotation axis of the table 21 (center of the fixing jig 110). In this embodiment, in order to set the four workpieces OB on the fixing jig 110, when the table 21 is rotated once, eight edges A (1), A (2) at the position of the radius r1 from the center. , A (3), A (4), A (5), A (6), A (7), A (8) can be detected. Therefore, the set position of the workpiece OB with respect to the table 21 can be calculated based on the edges A (1) to A (8). This set position calculation procedure will be described later.

  The light reception signal output from the second signal amplification circuit 66 is also input to the error detection circuit 76. The error detection circuit 76 is a circuit that detects an abnormal portion formed on the surface of the workpiece OB, and starts operation when receiving an instruction from the controller 90. As shown in FIG. 10, the error detection circuit 76 includes a non-setting level detection circuit 761, an in-setting level detection circuit 762, a delay circuit 763, and a switch circuit 764. The non-setting level detection circuit 761 has a normal range (first value) between the first reference level R1 and the second reference level R2 in which the signal level (crest value) of the received light reception signal is higher than the first reference level R1. (Corresponding to the normal range set by the mask signal generation circuit 67 in the embodiment), that is, when the signal level of the received light signal falls below the first reference level R1, or exceeds the second reference level R2. The second signal is output to the switch circuit 764.

On the other hand, the in-setting level detection circuit 762, when the signal level (peak value) of the received light reception signal enters the normal range from the state outside the normal range, that is, the signal level of the light reception signal is the first. A first signal is output when the reference level R1 increases from the state below the first reference level R1 to the first reference level R1, or when the reference level R2 decreases from the state above the second reference level R2 to the second reference level R2. . The delay circuit 763 receives the first signal output from the in-setting level detection circuit 762, delays the first signal by the delay amount d3, and outputs the delayed signal to the switch circuit 764. This delay amount d3 is instructed to the delay circuit 763 by the controller 90 in advance. The controller 90 calculates this delay amount d3 by the following equation.
d3 = (DS / v) + A
DS represents the interval (irradiation position interval) between the irradiation position of the processing laser beam and the irradiation position of the inspection laser beam on the surface of the processing object OB, and v represents the irradiation of the processing laser beam by the rotation of the table 21. The position is a linear velocity at which the position moves on the surface of the workpiece OB, and A is a positive fine value set in advance.

  Here, the transition of the peak value of the received light signal and the output timing of the first signal and the second signal will be described with reference to FIG. While the peak value of the received light signal falls between the first reference level R1 and the second reference level R2, no signal is output from the out-of-setting level detection circuit 761 and the in-setting level detection circuit 762. When the irradiation position (light spot) of the inspection laser beam enters the abnormal part of the workpiece OB, the peak value of the received light signal decreases and falls below the first reference level R1 (time t1). A second signal (a pulse signal having a predetermined width) is output from the detection circuit 761. Thereafter, when the irradiation position of the inspection laser beam exits from the abnormal part, the peak value of the received light signal increases. Output pulse signal). The delay circuit 763 outputs the first signal at the timing when the first signal is delayed by the delay amount d3, that is, at time t3 (= t2 + d3).

  The switch circuit 764 is a switch for switching output / interruption of the second signal output from the non-setting level detection circuit 761 and the first signal output from the delay circuit 763 to the signal switching circuit 83. The switch circuit 764 is configured to switch the open / close state of the switch in accordance with a signal from the switching signal generation circuit 56. When the second signal is input from the switching signal generation circuit 56, the switch circuit 764 turns off the switch and blocks the signal path from the unset level detection circuit 761 and the delay circuit 763 to the signal switching circuit 83. The signal output from the switching signal generation circuit 56 is also input to the signal switching circuit 83. Therefore, in this case, the signal switching circuit 83 connects the second focus servo system circuit 82 and the drive circuit 65 by the second signal from the switching signal generation circuit 56. That is, the focus servo system is switched to the second focus servo system.

  On the other hand, when the first signal is input from the switching signal generation circuit 56, the switch circuit 764 turns on the switch and connects the signal path from the unset level detection circuit 761 and the delay circuit 763 to the signal switching circuit 83. To do. Therefore, the second signal output from the non-setting level detection circuit 761 or the first signal output from the delay circuit 763 is output to the signal switching circuit 83.

  The switching signal generation circuit 56 outputs the first signal or the second signal according to the irradiation position of the processing laser light. For this purpose, the switching signal generation circuit 56 generates the switching signal at the position where the processing object OB is set on the table 21. It is necessary to grasp in advance on the circuit 56 side. Therefore, before performing laser processing, the operator operates the input device 91 to cause the controller 90 to execute a set position acquisition routine, and stores the set position of the processing object OB in the switching signal generation circuit 56. Hereinafter, a set position acquisition routine performed by the controller 90 will be described. FIG. 11 is a flowchart showing a set position acquisition routine. This set position acquisition routine is stored as a control program in the ROM of the controller 90, and is started in step S100. Prior to the execution of the set position acquisition routine, the same initial settings are made for the radial position detection circuit 52 and the feed motor control circuit 54 as when the laser processing routine of the first embodiment is started.

  First, in step S102, the controller 90 instructs the feed motor control circuit 54 to move to a preset set position detection radius position. As a result, the feed motor control circuit 54 inputs the radius position detected by the radius position detection circuit 52 until the irradiation position of the laser light coincides with the set position detection radius position having the radius r1 from the center of the table. The table 21 is moved by controlling the rotation of the feed motor 23. When the table 21 moves to the set position detection radius position in this way, the controller 90 instructs the spindle motor control circuit 53 to start the rotation of the spindle motor 22 at a low rotation speed in step S104. The spindle motor control circuit 53 calculates the rotation speed of the spindle motor 22 by using the A-phase signal and the B-phase signal from the encoder 22a, and the calculated rotation speed becomes equal to the low rotation speed input from the controller 90. Then, the rotation control of the spindle motor 22 is started.

  Subsequently, in step S106, the controller 90 instructs the first laser driving circuit 71 to start non-processing laser light irradiation, and then in step S108, the focus servo circuit 82c of the second focus servo system and An operation start is instructed to a circuit for driving a focus actuator 40 (not shown) and an S-shaped detection circuit. In this case, the controller 90 outputs a second signal to the signal switching circuit 83 to enable focus servo by the second focus servo system. As a result, the surface of the object OB is irradiated with the non-machining laser beam, and the optical axis direction of the objective lens 36 is adjusted so that the focal position coincides with the surface of the object OB or the fixing jig 110. Position control is started. In the second focus servo system, since the S-shaped detection distance of the second light receiving optical system is set to be long and the cut-off frequency of the focus servo circuit 82c is also set to be low, the focus servo cannot be removed. Next, the controller 90 instructs the second laser driving circuit 72 to start the inspection laser light irradiation in step S110. Thereby, the 2nd laser light source 41 is driven, and the laser beam for a test | inspection is irradiated to the surface of the workpiece OB.

  Subsequently, in step S112, the controller 90 instructs the edge detection circuit 75 and the rotation angle detection circuit 55 to start operation. Next, in step S114, the process waits for the rotation angle detected by the rotation angle detection circuit 55 to be equal to or smaller than the minimum value θa (the rotation angle becomes 0). When the rotation angle of the table 21 becomes equal to or smaller than the minimum value θa (S114: Yes), the controller 90 sets the value of the variable n to “1” in step S116, and the edge detection circuit 75 sends an edge in step S118. It is determined whether a detection signal is input. The controller 90 repeats the determination until the edge detection signal is input. When the edge detection signal is input (S118: Yes), the rotation angle A (n) output from the rotation angle detection circuit 55 in step S120. ) Is obtained and temporarily stored in a memory such as a RAM.

  Subsequently, in step S122, the controller 90 determines whether or not the value of the variable n is “8”. If n = 8 is not satisfied, the controller 90 increments the value of the variable n by “1” in step S124. Then, the process returns to step S118. Therefore, every time the edge detection signal output from the edge detection circuit 75 is input, the controller 90 sequentially stores digital data representing the rotation angle A (n) of the table 21 at that time. When eight pieces of data representing the rotation angle A (n) are stored in this way, the value of the variable n is 8, and the determination in step S122 is “Yes”.

  When the radial position r1 of the table 21 is set so that the light spot of the laser beam crosses the surface of each workpiece OB when the table 21 is rotated, the light spot is changed by rotating the table 21 once. An edge detection signal is output from the edge detection circuit 75 every time it passes through the edge of the workpiece OB. This edge detection signal is output twice when the light spot passes through one workpiece OB. Therefore, by detecting the edge detection signal eight times, the edges of all the processing objects OB are detected.

  If the controller 90 determines “Yes” in step S122, it advances the process to step S126, and instructs the focus servo circuit 82c to stop focus servo control. Subsequently, in step S128, the second laser driving circuit 72 is instructed to stop irradiation of the inspection laser light, and in step S130, the first laser driving circuit 71 is instructed to stop irradiation of the non-processing laser light. To do. Thereby, the irradiation of the inspection laser beam and the non-processing laser beam to the workpiece OB are stopped. Subsequently, the controller 90 instructs the spindle motor control circuit 53 to stop the rotation in step S132. Thereby, the rotation of the table 21 is stopped. In step S134, the edge detection circuit 75 and the rotation angle detection circuit 55 are instructed to stop operation.

Subsequently, in step S136, the controller 90 calculates the set position of the workpiece OB based on the eight rotation angles A (1) to A (8). As shown in FIG. 9, the set position of the processing object OB is represented by a rotation angle at which the processing object OB is arranged with respect to the table 21. The rotation angle at which the workpiece OB is arranged is that the laser beam irradiates a line connecting the origin that is the center of the table 21 (center of the fixing jig 110) and the center of each workpiece OB. Rotation angle C (1) to C (4) of the table 21 at the time. The rotation angles C (1) to C (4) are calculated as follows.
C (1) = (A (1) + A (2)) / 2
C (2) = (A (3) + A (4)) / 2
C (3) = (A (5) + A (6)) / 2
C (4) = (A (7) + A (8)) / 2

  Subsequently, the controller 90 writes data representing the rotation angles C (1) to C (4) in the memory in the switching signal generation circuit 56 in step S138. Thus, data representing the rotation angles C (1) to C (4) is stored in the memory of the switching signal generation circuit 56. When the controller 90 performs the process of step S138, the controller 90 ends the set position acquisition routine at step S140. When this set position acquisition routine is completed, laser processing is then started.

  FIG. 13 is a flowchart showing a laser processing routine in the second embodiment. This laser processing routine is stored in the ROM of the controller 90 as a control program. When carrying out laser processing, the operator inputs processing conditions and the like using the input device 91 and stores them in the controller 90 as in the first embodiment. Hereinafter, the laser processing routine will be described, but the same processing as in the first embodiment will be described briefly.

  When the laser processing routine is started in step S200, the controller 90 instructs the feed motor control circuit 54 to move to the input laser processing start radius position in step S202. Accordingly, the feed motor control circuit 54 drives and controls the feed motor 23 to move the table 21 to the laser processing start radius position. Subsequently, in step S204, the controller 90 calculates the rotation speed of the spindle motor 22 by using the input laser processing start radius position and rotation linear velocity, and sends the calculated rotation speed to the spindle motor control circuit 53. Outputs and instructs the spindle motor 22 to start rotating. As a result, the spindle motor 22 starts to rotate at the instructed rotational speed. After outputting the rotation start instruction, the controller 90 repeats the calculation of the rotation speed of the spindle motor 22 by an interrupt routine different from this routine, and the calculated rotation speed is sent to the spindle motor control circuit 53 each time. Output.

  Subsequently, the controller 90 outputs a second signal to the signal switching circuit 83 in step S206. As a result, the second focus servo system circuit 82 is connected to the drive circuit 65. Subsequently, in step S208, the controller 90 instructs the first laser drive circuit 71 to start irradiating non-processing laser light. As a result, the first laser drive circuit 71 starts outputting a non-machining level drive signal to the first laser light source 31, and the non-machining laser light is applied to the surface of the workpiece OB or the fixing jig 110. Irradiated. Subsequently, in step S210, the controller 90 instructs the focus servo circuits 81c and 82c, the circuit that drives the focus actuator 40 (not shown), and the S-shaped detection circuit to start operation. As a result, control for displacing the position of the objective lens 36 in the optical axis direction is started so that the focal position of the non-processing laser light always coincides with the surface of the processing object OB or the fixing jig 110. In this case, since the signal switching circuit 83 connects the second focus servo system circuit 82 and the drive circuit 65, focus servo control by the second focus servo system is started.

  Subsequently, in step S212, the controller 90 instructs the second laser driving circuit 72 to start irradiation of the inspection laser light. As a result, the second laser drive circuit 72 starts to output a drive signal having a constant inspection level to the second laser light source 41. Thus, a light spot of the inspection laser beam is formed on the surface of the workpiece OB or the fixing jig 110 at a position separated from the light spot of the non-processing laser beam by the irradiation position interval DS, and the reflected light of this light spot is formed. Is detected by the second photodetector 45.

  Subsequently, in step S214, the controller 90 instructs the feed motor control circuit 54 to start moving in the radial direction. In this case, the controller 90 calculates the moving speed based on the input rotational linear speed and processing pitch, and the radial position taken in from the radial position detecting circuit 52, and instructs the moving speed to the feed motor control circuit 54. . Thereby, the table 21 starts moving in the radial direction at the instructed moving speed. The controller 90 repeats the calculation of the moving speed of the table 21 by an interrupt routine different from this routine after instructing the start of moving in the radial direction, and each time the calculated moving speed is fed to the feed motor control circuit. To 54.

  Subsequently, the controller 90 instructs the rotation angle detection circuit 55, the switching signal generation circuit 56, and the error detection circuit 76 to start operation in step S216. Accordingly, the rotation angle detection circuit 55 starts to output a digital signal representing the rotation angle of the table 21 to the switching signal generation circuit 56. The switching signal generation circuit 56 starts to input the rotation angle of the table 21 detected by the rotation angle detection circuit 55, and outputs a first signal or a second signal to the signal switching circuit 83 based on the rotation angle. Starts output processing. The processing of the switching signal generation circuit 56 will be described in detail later, but the second focus servo system is selected when the processing laser light irradiates the boundary between the fixing jig 110 and the fixing jig 110 and the workpiece OB. The first signal or the second signal is output according to the rotation angle of the table 21 so that the first focus servo system is selected when the processing laser light irradiates the processing object OB. Further, when the controller 90 instructs the error detection circuit 76 to start operation, the controller 90 calculates the delay amount d3 (= (DS / v) + A) described above and outputs it to the delay circuit 763.

  Subsequently, in step S218, the controller 90 instructs the first laser driving circuit 71 to start irradiation of the processing laser light and instructs the light emission signal supply circuit 73 to output a signal. In response to this instruction, the first laser driving circuit 71 switches the driving signal output to the first laser light source 31 from the non-processing level to the processing level, and according to the waveform of the signal supplied from the light emission signal supply circuit 73. Make a waveform. Accordingly, the processing object OB is irradiated with the processing laser light instead of the non-processing laser light, and laser processing of the processing object OB is started.

  Subsequently, in step S220, the controller 90 takes in data representing the radial position output from the radial position detection circuit 52, and determines in step S222 whether or not the machining end radial position has been reached. The processing end radius position is a value input and set when the operator starts laser processing. The processes in steps S220 and S222 are repeated until the radius position detected by the radius position detection circuit 52 matches the machining end radius position. Accordingly, during this time, laser processing of the processing object OB is continued by irradiation of the processing laser light. At the same time, the error detection circuit 76 detects an abnormal portion based on the reflected light intensity of the inspection laser beam at the position immediately before laser processing and outputs a focus servo system switching signal (first signal or second signal). . The switching signal generation circuit 56 also performs output processing of a focus servo system switching signal (first signal or second signal) according to the rotation angle of the table 21.

  Here, the focus servo system switching signal output processing performed by the switching signal generation circuit 56 will be described. FIG. 14 is a flowchart showing a focus servo system switching signal output routine performed by the switching signal generation circuit 56. This focus servo system switching signal output routine is stored in the ROM of the switching signal generation circuit 56 as a control program. In response to an operation start instruction from the controller 90 (FIG. 13: step S216), the switching signal generation circuit 56 starts a focus servo system switching signal output routine in step S300.

  The switching signal generation circuit 56 first takes in a signal representing the rotation angle of the table 21 from the rotation angle detection circuit 55 in step S302. Subsequently, in step S304, the process waits for the rotation angle detected by the rotation angle detection circuit 55 to be equal to or smaller than a preset minute value θa (the rotation angle becomes 0). In step S306, the value of the variable n is set. Set to “1”. In step S308, a signal representing the radial position output from the radial position detection circuit 52 is captured.

Subsequently, the switching signal generation circuit 56 calculates the signal output angles D (1) to D (8) in step S310. As shown in FIG. 9, the signal output angles D (1) to D (8) are such that the irradiation position of the processing laser beam is slightly from the boundary between the processing object OB and the fixing jig 110. This is the rotation angle of the table 21 when passing through the side point, and is specifically calculated as the following equation.
D (1) = C (1) -Θ + ΔΘ
D (2) = C (1) + Θ−ΔΘ
D (3) = C (2) -Θ + ΔΘ
D (4) = C (2) + Θ−ΔΘ
D (5) = C (3) -Θ + ΔΘ
D (6) = C (3) + Θ−ΔΘ
D (7) = C (4) -Θ + ΔΘ
D (8) = C (4) + Θ−ΔΘ

Here, Θ is a line connecting the point where the movement locus (circle of radius a) of the optical spot of the processing laser beam on the processing object OB intersects the boundary of the processing object OB and the rotation center of the table 21; This is the angle formed by the line connecting the center of the workpiece OB and the rotation center of the table 21. The memory of the switching signal generation circuit 56 stores a distance rc from the center of rotation of the table 21 to the center of the workpiece OB and a radius value rk of the workpiece OB. Further, the distance a from the rotation center of the table 21 to the irradiation position of the processing laser light is taken in as a radial position in step S308. Therefore, Θ can be calculated from the relationship rk ² = a ² + rc ² −2 · a · rc · cos Θ since the distance rc, the radius value rk, and the distance a are known. ΔΘ is a minute angle set in advance corresponding to the radial position (distance a) in order to specify a point near the boundary on the surface of the workpiece OB. Is remembered.

  Subsequently, the switching signal generation circuit 56 takes in a signal representing the rotation angle of the table 21 from the rotation angle detection circuit 55 in step S312. Subsequently, in step S314, it is determined whether the rotation angle is equal to or greater than the signal output angle D (n). If the rotation angle has not reached the signal output angle D (n) (S314: No), it is determined in step S316 whether an operation stop command has been received from the controller 90, and no operation stop command has been received. If so, the process returns to step S312. The switching signal generation circuit 56 repeats the processing of steps S312 to S316 while receiving no operation stop command from the controller 90, and when the rotation angle of the table 21 reaches D (n) (S314: Yes), the processing is performed. Moving to step S318, it is determined whether or not the value of the variable n is an even number. If the value of the variable n is an even number, the second signal is output to the signal switching circuit 83 in step S320, and if the value of the variable n is an odd number, the first signal is output to the signal switching circuit 83 in step S322.

  When the switching signal generating circuit 56 outputs the first signal or the second signal in step S320 or S322, next, in step S324, it is determined whether or not the value of the variable n has reached “8”. If the value of variable n has not reached “8”, the value of variable n is incremented by “1” in step S326, and the process returns to step S312. Therefore, every time the rotation angle of the table 21 reaches the signal output angle D (n), the switching signal generation circuit 56 outputs the second signal if the value of the variable n is an even number, and sets the variable n to an odd number. For example, the first signal is output to the signal switching circuit 83.

  When such processing is repeated and the value of the variable n reaches “8”, the switching signal generation circuit 56 returns the processing to step S306, and the signal output angles D (1) to D (D) corresponding to the new radial positions. 8) is calculated (S308 to S310), and the first signal or the second signal is output to the signal switching circuit 83 every time the rotation angle of the table 21 reaches the signal output angle D (n) (S312 to S326). When an operation stop command is input from the controller 90, the focus servo system switching signal output routine ends in step S328.

  According to this focus servo system switching signal output routine, from the state in which the processing laser light irradiates the fixing jig 110 (for example, the rotation angle 0 in FIG. 9), the irradiation position of the processing laser light is the processing object. When a point (for example, D (1) shown in FIG. 9) that passes the boundary between the OB and the fixing jig 110 and passes the edge of the workpiece OB by a predetermined distance is reached, the first signal is output from the switching signal generation circuit 56. Is output. Accordingly, the focus servo signal of the first focus servo system circuit 81 is output to the drive circuit 65 after the processing laser light starts irradiating the processing object OB. Thereby, focus servo control with good followability using the first light receiving optical system is performed.

  When the irradiation position of the processing laser light reaches a point (for example, D (2) in FIG. 9) that is a predetermined distance before the edge on the opposite side of the processing object OB, the second signal is output from the switching signal generation circuit 56. Is done. Accordingly, the focus servo signal of the second focus servo system circuit 82 is replaced by the drive circuit 65 before the processing laser light irradiates the boundary between the processing object OB and the fixing jig 110 instead of the first focus servo system circuit 81. Is output. As a result, focus servo control with a wide focus position control range and strong noise resistance is performed.

Note that the calculation of the focus servo system switching signal output routine and the signal output angle D (n) described above is performed on the line of the rotation angle 0 (the rotation angle of the table 21 when the index signal is input) as shown in FIG. This is an explanation for a case where the processing object OB is not arranged. Whether or not the workpiece OB is arranged on the line with the rotation angle 0 can be determined by calculation as follows. For example, in the set position acquisition routine, when the angles C (1) to C (4) at which the workpiece OB is arranged are calculated, B (1) is calculated by the following equation.
B (1) = C (1) −sin ⁻¹ (rk / rc)
If the calculated value B (1) is a negative value, a line having a rotation angle of 0 is arranged on the workpiece OB.

When the line with the rotation angle 0 is arranged on the workpiece OB, B (8) is calculated by the following equation.
B (8) = C (4) + sin ⁻¹ (rk / rc)
Then, the angle Θc from the intermediate line between the calculated values B (1) and B (8) to the line with the rotation angle 0 is calculated, and the calculated value Θc is stored in the memory of the switching signal generating circuit 56.

  In this case, in the focus servo system switching signal output routine of FIG. 14, the switching signal generation circuit 56 newly adds a value obtained by adding the angle Θc to the calculated values of the signal output angles D (1) to D (8) in step S310. The signal output angles D (1) to D (8) are set, and the angle Θc is added to the rotation angle obtained from the rotation angle detection circuit 55 also in the rotation angle taken in step S312. At that time, when the angle becomes equal to or greater than 360 ° (pulse count value corresponding to 360 °), 360 ° may be subtracted from the angle. Thereby, it can process as a line of the rotation angle 0 being located in the middle between the workpieces OB.

  Returning to the explanation of the laser processing routine of FIG. As described above, laser processing is started in step S218, and processing end timing is determined based on the radial position of the table 21 in steps S220 and S222. During such laser processing, the switching signal generation circuit 56 operates as described above, and outputs a switching signal (first signal or second signal) corresponding to the rotation angle of the table 21 to switch the focus servo system. This switching signal is also output to the switch circuit 764 of the error detection circuit 76 as shown in FIG.

  When the second signal is input from the switching signal generation circuit 56, the switch circuit 764 turns off the switch and blocks the signal path from the unset level detection circuit 761 and the delay circuit 763 to the signal switching circuit 83. Accordingly, the switch circuit 764 turns off the switch when the processing laser light is irradiating the fixing jig 110 and the boundary between the processing object OB and the fixing jig 110. The inspection laser light irradiates a position away from the irradiation position of the processing laser light in the processing direction (the direction opposite to the rotation direction of the table 21). It can be ignored compared to the corresponding irradiation trajectory distance. Therefore, when the inspection laser light is radiating the fixing jig 110 and the boundary between the workpiece OB and the fixing jig 110, the error detection circuit 76 sends a switching signal (first signal) to the signal switching circuit 83. Or the second signal) is not output.

  In addition, when the first signal is input from the switching signal generation circuit 56, the switch circuit 764 turns on the switch and connects the signal path from the unset level detection circuit 761 and the delay circuit 763 to the signal switching circuit 83. To do. Accordingly, when the inspection laser light is irradiating the surface of the workpiece OB, the switch circuit 764 outputs a switching signal corresponding to the inspection result of the surface of the workpiece OB inspected by the error detection circuit 76 to the signal switching circuit. Output to 83. For example, when the inspection laser light is irradiating the surface of the workpiece OB, if the irradiation position of the inspection laser light enters an abnormal part, the peak value of the received light signal is reduced to a normal range (first reference level). R2 and the second reference level R2), and the second signal is output from the non-setting level detection circuit 761 (FIG. 12: time t1). The second signal is output to the signal switching circuit 83 via the switch circuit 764. For this reason, the first focus servo system is switched to the second focus servo system.

  On the other hand, the light spot of the processing laser light enters the abnormal portion with a delay of the time obtained by dividing the irradiation position interval DS by the linear velocity v. For this reason, the intensity of the reflected light of the processing laser light changes with a delay by that time, as shown by the broken line in FIG. At this time, since it has been switched to the second focus servo system using the second light receiving optical system having a long S-shaped detection distance, the focus servo even if the distance between the objective lens 36 and the irradiation surface varies greatly due to the abnormal part. Does not come off.

  When the irradiation position of the inspection laser light passes through the abnormal part, the peak value of the received light signal returns to the normal range, and the first signal is output from the setting level detection circuit 762 to the delay circuit 763 (FIG. 12: time t2). The delay circuit 763 delays the first signal by the delay amount d3 and outputs it to the signal switching circuit 83 (FIG. 12: time t3). When the first signal is input, the signal switching circuit 83 switches the output signal from the signal by the second focus servo system to the signal by the first focus servo system. The timing at which the focus servo system is switched is after the irradiation position of the processing laser light passes through the abnormal portion. Accordingly, even if the first focus servo system using the first light receiving optical system having a short S-shaped detection distance is switched, the focus servo is not deviated and laser processing can be performed with high accuracy.

  When such processing is repeated and it is determined in step S222 that the radial position of the table 21 has reached the machining end radial position, the controller 90 instructs the focus servo circuits 81c and 82c to stop operating in step S224. To stop focus servo control. Next, in step S226, the controller 90 instructs the second laser drive circuit 72 to stop irradiating the inspection laser light, and in step S228, the controller 90 irradiates the first laser drive circuit 71 with the processing laser light. Instruct to stop. Thereby, irradiation of the inspection laser beam and the processing laser beam is stopped. Subsequently, in step S230, the controller 90 instructs the rotation angle detection circuit 55, the switching signal generation circuit 56, and the error detection circuit 76 to stop operating.

  Subsequently, the controller 90 instructs the spindle motor control circuit 53 to stop rotation in step S232, and instructs the feed motor control circuit 54 to stop moving in the radial direction in step S234. Thereby, the spindle motor 22 and the feed motor 23 are stopped. When the rotation of the table 21 and the movement in the radial direction are stopped in this manner, the laser processing routine is ended in step S236.

  According to the laser processing apparatus 2 of the second embodiment described above, since a plurality of workpieces OB are laser processed simultaneously, production efficiency can be improved. Moreover, the focus servo control mode is different depending on the case where the processing laser light irradiates the fixing jig 110 and the boundary between the processing object OB and the fixing jig 110 and the case where the processing object OB is irradiated. In the former case, since the focus servo control is performed by the second focus servo system having a wide focal position control range and a low cut-off frequency, the focus servo does not deviate from disturbances such as the step Δt and the gap Δx. In the latter case, since the focus servo control is performed by the first focus servo system having good followability with respect to the displacement of the irradiated surface, the processing accuracy of the laser processing can be maintained well. Further, even when the processing object OB is irradiated with the processing laser beam and the laser processing is performed, the second focus is detected when the abnormal portion is detected from the reflected light of the inspection laser beam at the position immediately before the laser processing. Since the focus servo control is maintained until the processing laser light is switched to focus servo control and the irradiation position of the processing laser light passes through the abnormal portion, the focus servo is not deviated by the abnormal portion. Accordingly, normal laser processing can be continued, and loss of the processing object OB and waste of processing time can be reduced. As a result, production efficiency can be further improved.

  The control mode in which the focus servo control is performed in the first focus servo system corresponds to the normal mode of the present invention, and the control mode in which the focus servo control is performed in the second focus servo system when an abnormal portion is detected is the abnormality of the present invention. This corresponds to the detection mode. In the error detection circuit 76, a period from when the first signal is output from the non-setting level detection circuit 761 to when the second signal is output from the setting level detection circuit 762 corresponds to the abnormal period of the present invention. The period from when the first signal is output by the non-setting level detection circuit 761 to when the second signal is output by the delay circuit 763 corresponds to the control mode switching period of the present invention.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the object of the present invention.

  For example, in the first embodiment, while the hold signal is at a high level, the focus servo is held by outputting the focus error signal as zero to the focus servo circuit 64, but for example, the focus servo circuit 46 or the drive In the circuit 50, the focus servo may be held by continuing the output signal immediately before the hold signal becomes high level. Also by this, the same effect as the first embodiment can be obtained.

  In the first embodiment, after detecting the abnormal part of the workpiece OB, the hold signal is output after being delayed by the delay amount d1, but the abnormal part is detected from the reflected light of the inspection laser light. The hold signal is set to the high level from the time point (time t1 in FIG. 3), and a minute time is added to the time obtained by dividing the irradiation position interval DS by the linear velocity v from the time point (time t2 in FIG. 3) when the abnormal part is not detected. When the added time (for example, the delay amount d2 in FIG. 3) elapses, the hold signal may be lowered to a low level to release the hold. According to this, the circuit configuration is simplified and the cost can be reduced.

  In this embodiment, the disk-shaped table 21 is used as a set part for setting the workpiece OB. However, as shown in FIG. 15, a laser provided with a drum-shaped fixing jig 121 as a set part. The processing device 3 may be used. This laser processing apparatus 3 includes a moving stage 140 that is rotatably provided with a fixing jig 121, a spindle motor 122 that is fixed to the moving stage 140 and rotates the fixing jig 121, and the axis of the fixing jig 121. A stage guide 141 that is movably supported in the direction, a screw feed mechanism 142 provided on the stage guide 141, a feed motor 123 that moves the moving stage 140 via the screw feed mechanism 142, and a stage guide 141. And a machining head 130 fixed to the head support frame 143. The spindle motor 122, the feed motor 123, and the machining head 130 correspond to the spindle motor 22, the feed motor 23, and the machining head 30 of the first embodiment. In the laser processing apparatus 3, a sheet-like workpiece OB ′ is wound and set on the fixing jig 121, and is sent in the axial direction while rotating the fixing jig 121 around the central axis. A configuration is adopted in which the irradiation position of the irradiated laser light (processing laser light and inspection laser light) is moved over the entire surface of the processing object OB ′.

  Further, in the second embodiment, the laser processing apparatus has been described in which a plurality of processing objects OB are arranged on the same circumference on the table 21 and simultaneously perform laser processing. However, one disk-shaped processing object OB has been described. A laser processing apparatus that performs laser processing by setting the center of the table 21 or a laser processing apparatus that performs laser processing by setting a single sheet-like object OB ′ on a drum-shaped fixing jig 121. It can also be applied. In this case, since the processing laser light does not irradiate the surface of the fixing jig, the focus servo system may be switched based only on the detection of the abnormal part.

  In this embodiment, when changing the relative position between the machining head 30 and the table 21, a configuration is adopted in which the table 21 is moved in the radial direction. However, the machining head 30 is moved in the radial direction of the table 21. It may be configured to be moved. Further, both the table 21 and the processing head 30 can be moved in association with each other. In the case of the laser processing apparatus 3 shown in FIG. 15 provided with the drum-shaped fixing jig 121, the processing head 130 is moved in the axial direction of the fixing jig 121 without moving the fixing jig 121 in the axial direction. It may be configured to be moved. Also by this, the same effect as the above-described embodiment can be obtained.

  In this embodiment, the surface of the workpiece OB is laser-processed by irradiating the processing laser beam. This laser processing is a process of directly forming pits or continuous grooves on the workpiece OB. In addition, a reaction trace in which pits and continuous grooves are formed by the action of a developing solution in a subsequent process may be used.

  Further, in the present embodiment, the amplification factor of the second signal amplification circuit 66 is constant. However, when the reflectance of the processing object OB varies greatly from one individual to another, according to the reflectance of the processing object OB. The level of the signal output from the second signal amplifier circuit 66 may be constant by changing the amplification factor. In this case, a signal obtained by removing the high frequency component of the signal output from the second signal amplification circuit 66 by the low-pass filter is fed back to the second signal amplification circuit 66, and the amplification factor is changed so that the intensity of the signal becomes constant. What should I do? Alternatively, the amplitude of a portion excluding the abnormal portion of the signal output from the second signal amplifier circuit 66 may be detected, and the amplification factor may be changed so that the amplitude becomes constant. According to this, even if the reflectance of the processing object OB varies from individual to individual, the level of the signal output from the second signal amplification circuit 66 is constant, so that an abnormality is detected regardless of the reflectance of the processing object OB. Can be made constant.

  In the present embodiment, the reflected light intensity of the inspection laser beam is detected by the second photodetector 45. Instead of this, the reflected light is reflected for each light receiving area using a photodetector divided into a plurality of light receiving areas. The intensity may be detected, and abnormality detection may be performed based on a calculation result obtained by an arithmetic expression using the detected reflected light intensity. For example, as a photodetector that receives the reflected light of the inspection laser beam, a photodetector configured by a four-divided light receiving element similar to the first photodetector 39 of the present embodiment is used. Then, (a + d) − (b + c) is calculated using the intensities (a, b, c, d) of the reflected light incident on the four light receiving regions (A, B, C, D) arranged clockwise. Then, the abnormal period can be detected by comparing the calculated value which is the calculation result with a preset reference value (or reference range). In this case, the signal changes in an S shape at an abnormal location. Therefore, it is preferable to set the abnormal period from the time when the calculated value crosses the reference value provided above and below from the reference range to the outside of the reference range until it crosses from the outside of the reference range to the inside of the reference range. . This also has the same effect as the above-described embodiment.

  In addition, a cylindrical lens is disposed in front of the quadrant photodetector, and (a + c) − (b + d) is calculated, that is, a focus error signal is generated, and the calculated value as a result of this calculation and a preset reference value (or The abnormal period can also be detected by comparing with the reference range. This also has the same effect as the above-described embodiment.

  Also, an abnormal period can be detected by providing a differentiating circuit and comparing a value obtained by differentiating the intensity of reflected light of the inspection laser light with time and a reference value (or reference range). Also in this case, at the abnormal location, the differential value obtained by differentiating the reflected light signal changes in an S shape, so that the differential value crosses the reference value provided above and below from the reference range toward the outside of the reference range. It is preferable to set the abnormal period from the outside of the reference range to the time of crossing into the reference range. This also has the same effect as the above-described embodiment.

  Further, even when the abnormal period is detected based on the calculation result obtained by the calculation formula using the intensity of the reflected light of the inspection laser beam as described above, according to the reflectance of the workpiece OB as described above. If the amplification factor of the second signal amplification circuit 66 is changed, the accuracy of abnormality detection can be made constant regardless of the reflectance of the workpiece OB. Further, if a signal obtained by dividing the calculation result of (a + d) − (b + c), (a + c) − (b + d) by (a + b + c + d), which is the total signal of the four-divided photodetectors, is used, the reflection of the workpiece OB is reflected. Regardless of the rate, the level of the calculated signal is constant, so that the accuracy of abnormality detection can be made constant.

  The table 21 in the present embodiment corresponds to the set unit of the present invention, the spindle motor 22 and the spindle motor control circuit 53 in the present embodiment correspond to the rotating means of the present invention, and the machining heads 30 and 300 in the present embodiment. Corresponds to the machining head of the present invention, and the feed motor 23 and the feed motor control circuit 54 in the present embodiment correspond to the feeding means of the present invention. The functional units of the first laser drive circuit 71 and the controller 90 that executes the laser processing routine in the present embodiment correspond to the laser processing control means of the present invention, and the first light receiving optical system, the first signal amplification in the present embodiment. The circuit 61, the focus error signal generation circuit 62, the focus servo circuit 64, the drive circuit 65, the focus actuator 40, the second light receiving optical system, the first focus servo system circuit 81, and the second focus servo system circuit 82 are the focus servo of the present invention. Corresponds to means. The first laser light source 31 in the present embodiment corresponds to the processing laser light source of the present invention, and the second laser light source 41 in the present embodiment corresponds to the inspection laser light source of the present invention. In addition, the functional unit of the controller 90 that performs the process of irradiating the inspection laser light (S18, S212) in the second laser driving circuit 72 and the laser processing routine in this embodiment corresponds to the inspection laser light irradiation control means of the present invention. The second photodetector 45 in the present embodiment corresponds to the light detection means of the present invention, and the mask signal generation circuit 67 and the error detection circuit 76 in the present embodiment correspond to the abnormal period detection means of the present invention. The delay circuit 68 and the error detection circuit 76 in FIG. 6 correspond to the switching period setting means of the present invention, and the conduction circuit 63 and the signal switching circuit 83 in the present embodiment correspond to the control mode switching means of the present invention. The first delay circuit 681 in the present embodiment corresponds to the first delay means of the present invention, and the second delay circuit 682 in the present embodiment corresponds to the second delay means of the present invention. In addition, the function units of the controller 90 that executes the edge detection circuit 75 and the set position acquisition routine in the present embodiment correspond to the boundary detection means of the present invention. Further, the switching signal generation circuit 56 in the present embodiment corresponds to the non-irradiation control mode switching means of the present invention.

  Further, the laser processing routine in the present embodiment corresponds to the irradiation step of the present invention, and the processing started in step S22 or S210 in the laser processing routine in the present embodiment corresponds to the focus servo control step of the present invention. In the laser processing routine of the embodiment, the processing of the mask signal generation circuit 67 or the processing of the error detection circuit 76 started in step S20 or S216 corresponds to the abnormal period detection step of the present invention. The processing of the delay circuit 68 started in step S20 or S216 or the processing of switching the signal switching circuit 83 by the error detection circuit 76 corresponds to the control mode switching step of the present invention.

1 is a system configuration diagram of a laser processing apparatus according to a first embodiment. It is a block diagram of the delay circuit which concerns on 1st Embodiment. It is a signal waveform diagram concerning a 1st embodiment. It is a flowchart showing the laser processing control routine which concerns on 1st Embodiment. It is a system block diagram of the laser processing apparatus which concerns on 2nd Embodiment. It is explanatory drawing explaining the setting method of the processing target object which concerns on 2nd Embodiment. It is a schematic perspective view showing the set state of the processing target object concerning 2nd Embodiment. It is sectional drawing showing the boundary of the workpiece and fixing jig which concern on 2nd Embodiment. It is explanatory drawing showing the set position of the processing target object which concerns on 2nd Embodiment. It is a block diagram of the error detection circuit which concerns on 2nd Embodiment. It is a flowchart showing the set position acquisition routine which concerns on 2nd Embodiment. It is a signal waveform diagram concerning a 2nd embodiment. It is a flowchart showing the laser processing control routine which concerns on 2nd Embodiment. It is a flowchart showing the focus servo system switching signal output routine which concerns on 2nd Embodiment. It is a schematic perspective view of the laser processing apparatus which has a drum-shaped fixing jig as a modification. It is a graph showing an S-shaped waveform signal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 2, 3 ... Laser processing apparatus, 21 ... Table, 22, 122 ... Spindle motor, 22a ... Encoder, 23, 123 ... Feed motor, 23a ... Encoder, 30, 130, 300 ... Processing head, 31 ... 1st laser Light source, 39 ... first photo detector, 36 ... objective lens, 40 ... focus actuator, 41 ... second laser light source, 45 ... second photo detector, 49 ... third photo detector, 52 ... radial position detection circuit, 53 ... spindle motor control circuit 54 ... feed motor control circuit, 55 ... rotation angle detection circuit, 62, 81b, 82b ... focus error signal generation circuit, 63 ... conduction circuit, 64, 81c, 82c ... focus servo circuit, 65 ... drive circuit, 67 ... mask Signal generating circuit, 68 ... delay circuit, 681 ... first delay circuit, 6 DESCRIPTION OF SYMBOLS 2 ... 2nd delay circuit, 683 ... Flip-flop circuit, 71 ... 1st laser drive circuit, 72 ... 2nd laser drive circuit, 75 ... Edge detection circuit, 76 ... Error determination circuit, 81 ... 1st focus servo system circuit, 82 ... second focus servo system circuit, 83 ... signal switching circuit, 90 ... controller, 91 ... input device, 92 ... display device, 110, 121 ... fixing jig, 110h ... fixed circular hole, 140 ... moving stage, 141 ... Stage guide, OB, OB '... work object.

Claims (10)

A set part for setting a workpiece;
Rotating means for rotating the set unit;
A processing head having a processing laser light source, condensing the processing laser light emitted from the processing laser light source by an objective lens and irradiating the processing object;
The set unit and the processing head so that the irradiation position of the processing laser light moves on the surface of the processing object in a direction orthogonal to an irradiation movement locus formed by rotation of the set unit. A feeding means for changing the relative position with
While controlling the operation of the rotating means and the feeding means, by outputting a drive signal to the processing laser light source and irradiating the processing laser light on the surface of the processing object, Laser processing control means for laser processing the surface;
Based on the reflected light of the machining laser beam from the workpiece, the objective lens is placed on the optical axis of the machining laser beam so that the focal position of the machining laser beam coincides with the surface of the workpiece. In a laser processing apparatus equipped with a focus servo means that performs focus servo control by driving in a direction,
The processing head includes an inspection laser light source that irradiates a position immediately before laser processing that is opposite to the rotation direction of the rotating unit with respect to the processing object irradiated with the processing laser light.
When laser processing is performed by the laser processing control means, a driving signal is output to the inspection laser light source, and an inspection laser light having an intensity that does not cause laser processing on the surface of the processing object is generated. Laser light irradiation control means for inspection to be emitted from,
A light detection means for detecting the intensity of reflected light of the inspection laser light irradiated on the surface of the workpiece;
Based on the intensity of the reflected light detected by the light detecting means, an abnormal period detecting means for detecting an abnormal period in which the state of the reflected light of the inspection laser light is out of a normal range;
A switching period setting unit that sets a control mode switching period in which an end time later than the end time of the abnormal period is set based on the abnormal period detected by the abnormal period detection unit;
During the control mode switching period set by the switching period setting means, the control mode of the focus servo means is switched from the normal mode to the abnormality detection mode, and the position of the objective lens is maintained, or more than in the normal mode. A laser processing apparatus, comprising: control mode switching means for performing focus servo control with a wide control range of a focal position of the processing laser beam.   The switching period setting unit divides an interval between the irradiation position of the processing laser beam and the irradiation position of the inspection laser beam by a linear velocity at which the irradiation position of the processing laser beam moves by the rotation of the rotating unit. 2. The laser processing apparatus according to claim 1, wherein a value is set as a theoretical delay time, and a control mode switching period in which an end time that is later than the theoretical delay time is set from the end time of the abnormal period is set. The switching period setting means includes
First delay means for delaying the start time of the control mode switching period by a first delay time shorter than the theoretical delay time with respect to the start time of the abnormal period;
3. The second delay means for delaying the end time of the control mode switching period by a second delay time longer than the theoretical delay time with respect to the end time of the abnormal period. Laser processing equipment.   2. The control mode switching means holds the position of the objective lens by holding so as not to change a drive signal for driving the objective lens only during the control mode switching period. The laser processing apparatus according to claim 3. The focus servo means includes
Reflected light of the processing laser beam from the object to be processed is received by a first light receiving optical system, and a focus error signal indicating a focus position deviation is generated from the received light signal. Based on the focus error signal A first focus servo system for driving the objective lens in the optical axis direction of the processing laser beam so that a focal position of the processing laser beam coincides with a surface of the processing target;
Reflected light of the laser beam for processing from the object to be processed is received by a second light receiving optical system, and a focus error signal indicating a focus position shift is generated from the received light signal. Based on the focus error signal A focus servo system for driving the objective lens in the optical axis direction of the processing laser beam so that a focal position of the processing laser beam coincides with a surface of the processing target; from the first first servo system; Can be selected with the second focus servo system with a wide focal position control range,
The control mode switching means outputs an instruction to operate the second focus servo system instead of the first focus servo system during the control mode switching period to the focus servo means. The laser processing apparatus according to any one of claims 1 to 3. The set unit arranges a plurality of workpieces on the same plane via a plate-like fixing jig in which a plurality of fixing circular holes for inserting and fixing a disk-like workpiece in the thickness direction are formed. Are fixed,
The focus servo means is configured such that, even when the processing laser beam is not irradiating the workpiece, the focus position of the processing laser beam coincides with the irradiation surface based on the reflected light from the irradiation surface. The objective lens is driven in the optical axis direction of the laser beam for processing so as to
Boundary detection means for detecting a boundary between the outer periphery of the workpiece inserted and fixed in the fixed circular hole and the fixed circular hole;
Based on the boundary detected by the boundary detection means, when the processing laser light irradiates the surface of the fixing jig including the boundary, the second servo servo system is operated with respect to the focus servo means. The laser processing apparatus according to claim 5, further comprising: a control mode switching unit that outputs an instruction when the workpiece is not irradiated.   The cutoff frequency for cutting the high frequency component of the focus error signal in the second focus servo system is set lower than the cutoff frequency for cutting the high frequency component of the focus error signal in the first focus servo system. The laser processing apparatus according to claim 6. A set part for setting a workpiece;
Rotating means for rotating the set unit;
A processing head for condensing and irradiating the processing object with a processing laser beam by an objective lens;
The set unit and the processing head so that the irradiation position of the processing laser light moves on the surface of the processing object in a direction orthogonal to an irradiation movement locus formed by rotation of the set unit. A feeding means for changing the relative position with
Based on the reflected light of the machining laser beam from the workpiece, the objective lens is placed on the optical axis of the machining laser beam so that the focal position of the machining laser beam coincides with the surface of the workpiece. In a laser processing method applied to a laser processing apparatus provided with a focus servo means that performs focus servo control by driving in a direction,
While controlling the operation of the rotating means and the feeding means, the processing head irradiates the processing laser light onto the surface of the processing object from the processing head to laser-process the surface of the processing object, and the processing laser Irradiation step of irradiating an inspection laser beam having a strength at which the surface of the object to be processed is not laser-processed at a position immediately before laser processing that is opposite to the rotation direction of the rotating means from the position at which the object is irradiated with light When,
When performing the irradiation step, the focus servo means moves the objective lens in the optical axis direction of the processing laser light so that the focal position of the processing laser light coincides with the surface of the processing object. A focus servo control step to drive,
When performing the irradiation step, the intensity of the reflected light of the inspection laser light irradiated on the surface of the workpiece is detected, and the reflection of the inspection laser light is based on the detected intensity of the reflected light. An abnormal period detection step for detecting an abnormal period in which the light state is out of the normal range;
Based on the abnormal period detected by the abnormal period detection step, a control mode switching period in which an end time later than the end time of the abnormal period is set is set, and the focus servo control is performed during the control mode switching period. The control mode in the step is switched from the normal mode to the abnormality detection mode to hold the position of the objective lens, or to perform focus servo control with a wider control range of the focus position of the processing laser light than in the normal mode And a control mode switching step.   9. The position of the objective lens is held in the control mode switching step by holding the driving signal for driving the objective lens so as not to change only during the control mode switching period. Laser processing method. The focus servo means includes
Reflected light of the processing laser beam from the object to be processed is received by a first light receiving optical system, and a focus error signal indicating a focus position deviation is generated from the received light signal. Based on the focus error signal A first focus servo system for driving the objective lens in the optical axis direction of the processing laser beam so that a focal position of the processing laser beam coincides with a surface of the processing target;
Reflected light of the laser beam for processing from the object to be processed is received by a second light receiving optical system, and a focus error signal indicating a focus position shift is generated from the received light signal. Based on the focus error signal A focus servo system for driving the objective lens in the optical axis direction of the processing laser beam so that a focal position of the processing laser beam coincides with a surface of the processing target; from the first first servo system; Can be selected with the second focus servo system with a wide focal position control range,
The control mode switching step outputs an instruction to operate the second focus servo system instead of the first focus servo system during the control mode switching period to the focus servo means. Item 9. A laser processing method according to Item 8.

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