JP2006289443A - Laser beam machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam machining device capable of securing stability of the optical axis of a laser beam and dealing with machining accuracy not more than a nanometer unit by arranging a position detector for monitoring the position of the optical axis of a laser beam and by correcting deviation of the optical axis of a laser beam to be emitted to a workpiece. <P>SOLUTION: This laser beam machining device 1 is equipped with: a light source 2 for outputting a laser beam; an optical path adjusting part 4 for adjusting the optical path of the laser beam; a first spectroscope 8 for separating the laser beam into spectral components; a movable base 6 having a prescribed movable area and a place for putting on a workpiece 11; a movable base position detector 12 for detecting the position of the movable base; a first optical axis position detector 10 for detecting the optical axis of the spectral laser beam; a stage 7 on which the movable base, the movable base position detector and the first optical axis position detector are placed; and an optical axis controller 5 which receives an output from the first optical axis position detector to control the optical path adjusting part and to adjust the optical axis of the spectral laser beam. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laser processing apparatus, and more particularly to a laser processing apparatus having an accuracy of nanometer order or more.

  In general, a laser processing apparatus includes a laser light source that irradiates a workpiece, and a precision table having an earthquake resistance provided with a movable table on which the workpiece is placed, and a laser output from the laser light source. A step of processing a workpiece by fixing a reference point of light and moving the movable table on an XY plane on a precision table; In this processing step, errors in the position detector that detects the position of the movable table on the precision table and errors in the optical axis of the laser beam caused by the light guide from the laser light source to the workpiece can be considered. The accuracy of the position detector is 10 nm or less, and the stability accuracy of the optical axis of the laser beam output from the laser light source is realized to the microradian level.

  Patent Document 1 discloses a condensing position detection device for a condensing optical system in a laser processing apparatus that enables measurement of an irradiation position of laser light. The condensing position detection device includes a plurality of light receiving elements arranged in a matrix, a position sensor that is detachably disposed at a predetermined position of an XY table, and a laser beam emitted toward the position sensor. A discriminating device for detecting the output of each light receiving element constituting the position sensor and discriminating the condensing position of the laser beam; An arithmetic unit for calculation is provided.

  In this apparatus, the position sensor is attached to the XY table so that the XY coordinate axis of the XY table matches the coordinate axis of the position sensor in the XY direction, and the XY table is moved to a predetermined position. Then, the position sensor is focused and irradiated with laser light. Then, the output of each light receiving element constituting the position sensor is detected, it is determined which light receiving element is receiving the laser light, and the coordinate position from the origin of the position sensor of the light receiving element is obtained, thereby collecting the laser light. The light position can be determined.

JP-A-6-23577

The laser beam position detection device of Patent Document 1 is arranged on a detachable movable table, and if the processing technology has an accuracy of micrometer unit, the stability of the optical axis of the laser beam is at the microradian level. Since it is allowable, the position of the movable table can be controlled appropriately.
However, if the machining accuracy is nanometers or less, the error of the laser processing device can be tolerated by the position detector of the movable table, but the fluctuation of the optical axis of the laser beam is not allowed, and the laser beam irradiation point Errors due to the stability of the problem become a problem.
The present invention provides an optical axis position detector for monitoring the position of the optical axis of the laser beam, and corrects the deviation of the optical axis of the laser beam irradiated to the workpiece, thereby processing the nanometer unit or less. It aims at providing the laser processing apparatus which can respond to a precision.

(1) In order to achieve the above object, a laser processing apparatus according to the present invention includes:
A light source that outputs laser light;
An optical path adjustment unit for adjusting the optical path of the laser beam;
A first spectroscope for splitting laser light;
A movable table having a predetermined range of motion on which a workpiece is placed;
A movable table position detector for detecting the position of the movable table;
A first optical axis position detector for detecting the position of the optical axis of the split laser beam;
A stage on which the movable table, the movable table position detector, and the first optical axis position detector are mounted;
An optical axis control unit that receives the output from the first optical axis position detector and controls the optical path adjustment unit, and adjusts the optical axis of the dispersed laser beam;
It comprises.
(2) Moreover, it is preferable that the optical axis control part in the laser processing apparatus which concerns on this invention performs fuzzy control.
(3) Furthermore, a laser processing apparatus according to the present invention includes a second spectrometer that further divides the dispersed laser light, and a second optical axis for detecting the position of the optical axis dispersed by the second spectrometer. Preferably, a position detector is further provided, and the optical axis control unit is controlled so that the first optical axis position detector and the second optical axis position detector detect the laser beam at a predetermined position.
(4) Furthermore, at least one of the first optical axis position detector and the second optical axis position detector in the laser processing apparatus according to the present invention is split by the laser beam dispersed by the first spectrometer or the second spectrometer. It is preferable to detect the position of the optical axis of each laser beam by the reflected laser beam being reflected by a spherical reflecting surface and received by a four-quadrant sensor.
(5) Furthermore, the laser processing apparatus according to the present invention is provided between the first spectrometer and the first optical axis position detector or between the second spectrometer and the second optical axis position detector. It is preferable to arrange a pin hole having a predetermined diameter for allowing laser light to pass through at least one of them.

(1) According to the first aspect of the present invention, in the light guide path until the workpiece is irradiated with the laser beam output from the laser light source, the optical axis of the laser beam causes a shake of about microradians, and the position of the irradiation point Therefore, for example, a first optical axis position detector composed of light receiving elements arranged in a matrix is arranged in the vicinity of the movable base, and a laser beam for position detection is dispersed to detect the first optical axis position. The optical axis of the split laser beam is received by the instrument, the deviation from the reference position is calculated by detecting the reference position of the optical axis of the received laser beam, and the optical path adjustment unit is adjusted based on the calculated value. By modifying the light guide path, it is possible to realize a laser processing apparatus corresponding to an accuracy of nanometer units or less.
(2) Since the invention according to claim 2 performs fuzzy control, even if a deviation occurs in the optical axis of the laser beam, the deviation of the optical axis can be gradually corrected, and laser processing can be performed with a minimum error.
(3) The invention according to claim 3 controls the optical axis control unit so that the first optical axis position detector and the second optical axis position detector detect the laser beam at a predetermined position. Two reference points for the optical axis of the light are provided. For example, the optical path adjustment unit is adjusted so as to maintain the two reference points at equal intervals, thereby correcting the optical path and improving the correction accuracy.
(4) In the invention according to claim 4, since the position of the optical axis of each laser beam is detected by being reflected by the spherical reflecting surface and received by the four-quadrant sensor, each laser beam having a predetermined light diameter is detected. It is possible to irradiate the light receiving element and correct the optical axis so that the received light intensity (light receiving area) is kept uniform. Further, the light receiving surface of the laser beam can be set at an arbitrary place, and the design of the laser processing apparatus is flexible.
(5) In the invention according to claim 5, since the pinhole having a predetermined diameter for allowing the laser beam to pass through is arranged, the laser beam can be narrowed down to a desired beam diameter.

  The preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the drawings, the same reference numerals are used for the same elements, and the description thereof may be omitted as appropriate.

  FIG. 1 shows an overall schematic diagram of a laser processing apparatus 1 according to the present invention having nano-unit accuracy. The laser processing apparatus 1 includes a light source 2, an optical path adjustment unit 4, a semi-transparent mirror (first spectroscope) 8, a total reflection mirror 13, a movable base 6, a movable base position detector 12, and a first optical axis position detector (light Detector) 10, stage 7, optical axis controller 5, and condensing lenses 9, 9 '. All the components 1 to 12 are arranged on the vibration isolation table 3.

  The laser light source 2 outputs a femtosecond laser or UV laser light as a fundamental wave. The optical path adjustment unit 4 (see FIG. 8 for details) has a plurality of total reflection mirrors (two in FIG. 8: 22 and 24) that reflect the laser light input from the laser light source 2, and the total reflection mirror includes Is provided with a plurality of motors (four in FIG. 8: M1 to M4) for changing the reflection angle of the laser beam. As will be described later, the motor receives a signal from the optical axis controller 5, adjusts the angle of the reflection surface of the total reflection mirror, and positions the laser beam at a predetermined optical axis position. The semi-transparent mirror 8 is disposed on the optical axis of the laser beam output from the optical path adjusting unit 4 and separates the laser beam. The movable stage 6 moves within a predetermined movable range in a state where the workpiece 11 irradiated with the laser beam reflected by the total reflection mirror 13 and condensed by the condenser lens 9 ′ is placed and fixed. Can do. The movable table position detector 12 can detect the position of the movement error of the movable table 6 with an accuracy of 10 nm. The first optical axis position detector (photodetector) 10 is disposed in the vicinity of the movable table position detector 12 in order to accurately adjust the optical axis of the laser light in the vicinity of the processing laser light. It is comprised from several light receiving elements, such as a pixel in CCD arrange | positioned. The stage 7 irradiates the light receiving surface of the first optical axis position detector 10 with the optical axis of the laser light condensed by the condenser lens 9, and the optical axis of the laser light condensed by the condenser lens 9 ′. The movable table 6, the movable table position detector 12, and the first optical axis position detector 10 are arranged on the same plane so that the workpiece 11 is irradiated. The optical axis control unit 5 includes an adjustment value calculation means 26 and a motor control unit 28 (see FIG. 8), and outputs the received light intensity of the laser light received by the first optical axis position detector 10 as will be described later. Then, the optical path adjusting unit 4 is fuzzy controlled to fix the optical axis of the dispersed laser light at a fixed reference position.

Next, the light guide for laser light output from the laser light source 2 in the laser processing apparatus 1 of the present invention will be described.
First, laser light is output from the light source 2 toward the optical path adjustment unit 4. Next, the optical path adjustment unit 4 adjusts the optical path of the laser beam to be fixed at a predetermined position in order to irradiate the workpiece 11. Further, the laser beam that has passed through the optical path adjusting unit 4 is split into a laser beam that passes through the half mirror 8 and a laser beam that is branched from the half mirror 8. The laser beam that has passed through the semi-transparent mirror 8 is reflected by the total reflection mirror 13, and irradiates the workpiece 11 through the condenser lens 9 'to perform desired processing. The laser beam split from the half mirror 8 irradiates the first optical axis position detector 10 via the condenser lens 9.
As described above, the light guide path in the laser processing apparatus according to the present invention is formed.

Next, a mechanism for adjusting the optical path from the laser light source 2 to the first optical axis position detector 10 in FIG. 1 will be described in detail with reference to FIG.
The optical path adjustment unit 4 includes two total reflection mirrors 22 and 24, and each total reflection mirror 22 and 24 adjusts the angle of the reflection surface that reflects the laser light output from the laser light source 2. , M2, M3, and M4. The spectroscope 44 includes a semi-transparent mirror 8 that splits incident laser light and a condenser lens 9.

  As described above, the laser light output from the laser light source 2 is incident on the optical path adjustment unit 4, positioned at a predetermined optical axis position by the total reflection mirrors 22 and 24, and output. The output laser light is incident on the semi-transparent mirror 8 in the spectroscope 44. The semi-transparent mirror 8 separates laser light incident on the first optical axis position detector 10 from laser light incident on a workpiece (not shown). The split laser light is incident on the condensing lens 9 and is condensed and irradiated on a predetermined light receiving element (see FIGS. 2 to 4) of the first position detector 10. The light receiving element of the first optical axis position detector 10 converts the received laser light into an electrical signal proportional to the intensity and outputs the electrical signal. Since the output electric signal is generally weak in intensity, it is amplified by the amplifier 34 and then input to the adjustment value calculation means 26 in the optical axis controller 5. The adjustment value calculation means 26 calculates the amount of rotation of each of the motors M1 to M4 using fuzzy inference based on the electric signal amplified by the amplifier. A mechanism for calculating the rotation amounts (adjustment amounts) of the motors M1 to M4 using fuzzy inference will be described later. The rotation amounts of the motors M1 to M4 calculated by the adjustment value calculation unit 26 are transmitted to the motor control unit 28 that controls the motors M1 to M4. Next, a signal indicating each rotation amount is transmitted from the motor control unit 28 to each of the motors M1 to M4, and the motors M1 to M4 are driven. Thereby, the directions of the reflecting surfaces of the total reflection mirrors 22 and 24 are adjusted, and the optical path and optical axis of the laser light are adjusted.

Next, the light receiving element in the first optical axis position detector 10 will be described with reference to FIGS.
2 and 3, the pixels 21 are arranged in a matrix, and the pixel interval A is about 2 μm. FIG. 2 shows an embodiment (reference numeral 20) in which the irradiation point of the laser beam is completely irradiated with only one pixel as a reference pixel, and the received light intensity of the laser beam is measured by the reference pixel. Then, when the laser beam is shaken and a portion where the pixel is not irradiated is generated, the light receiving element senses the decrease in the received light intensity and completely irradiates the reference pixel so that the received light intensity becomes the maximum. In addition, the optical path controller 4 adjusts the optical path adjuster 4. FIG. 3 shows an embodiment (reference numeral 30) in which the irradiation point of the laser light uniformly irradiates a part of the four pixels forming the four quadrant sensor, and the irradiation area S1 to S1 in each pixel 21 is shown. The reference irradiation point of the laser beam to be irradiated uniformly at S4 is set. When the optical axis of the laser beam fluctuates and an imbalance occurs in the irradiation areas S <b> 1 to S <b> 4 of each pixel 21, the optical path controller 5 adjusts the optical path so that the received light intensity in each pixel 21 is equalized. Adjust part 4.

  FIG. 4 discloses a modified embodiment relating to the arrangement of the light receiving elements in the first optical axis position detector 10. In this embodiment, a reflection sphere 41 for reflecting laser light is disposed between the condenser lens 9 and the first optical axis position detector 10, and the laser light dispersed from the semi-transparent mirror 8 is reflected on the reflection sphere 41. The reflection surface of the laser beam is preferably reflected in the vertical direction with respect to the optical axis of the laser beam, and, for example, four pixels forming a four-quadrant sensor disposed on a plane 40 parallel to the optical axis are formed as shown in FIG. Similar irradiation reference points are set. When the optical axis of the laser beam fluctuates and an imbalance occurs in the irradiation area of each pixel, the optical axis control unit 5 adjusts the optical path adjustment unit 4 so that the received light intensity in each pixel is equalized. .

  Next, a modified embodiment in which the position of the optical axis of the laser beam is detected using the first optical axis position detector and the second optical axis position detector will be described with reference to FIG. In the present embodiment, the second semi-transparent mirror (second spectroscope) 16 is on the light guide path of the laser light dispersed by the semi-transparent mirror 8 and between the semi-transparent mirror 8 and the first optical axis position detector 10. Is arranged. The second semi-transparent mirror 16 further splits the laser light, and the split laser light is reflected by the total reflection mirror 18 and irradiated to the second optical axis position detector 15. Both the second semitransparent mirror 16 and the second total reflection mirror 18 are supported by a mirror support 50. The second optical axis position detector 15 may be either the same type as the first optical axis position detector 10 or a different type. As described above, in any optical axis position detector, the reference point for irradiating the laser beam in the light receiving element is set, and the optical path controller 5 is operated so that the distance between the two reference points is equal, thereby adjusting the optical path. Control part 4.

  Next, the modified embodiment of FIG. 4 will be described with reference to FIG. 6 is different from the embodiment of FIG. 4 in that a pinhole 42 is disposed between the reflection sphere 41 and a surface 40 on which four pixels forming a four-quadrant sensor are disposed. The pinhole 42 can reduce the light diameter of the laser light to a desired diameter, and the irradiation at each pixel corresponds to the reduction in diameter by reducing the mutual interval between the four pixels forming the 4-quadrant sensor. An area can be secured.

  FIG. 7 is an enlarged view showing a state in which the pinhole 72 supported by the support base 71 is disposed between the condenser lens 9 and the first optical axis position detector 10 in FIG. Also in this embodiment, the light diameter of the laser light can be reduced and the first optical axis position detector can be irradiated.

  FIG. 9 shows a result of performing control so that the light receiving intensity of the first optical axis position detector 10 is stabilized at the maximum value by adjusting the optical axis of the laser beam in the optical path adjusting unit 4. It is a graph that qualitatively depicts how changes occur. The horizontal axis shows time, and the vertical axis shows received light intensity on an arbitrary scale.

  As described above, the process of adjusting the optical path or optical axis from the laser light source 2 to the first optical axis position detector 10 in FIG. After t ′, the intensity of the incident light reaches a maximum value, and then fluctuates within an allowable range set as an allowable change in the intensity of the incident light (a range indicated by P in FIG. 9). If so, the output intensity in the first optical axis position detection device in the laser processing device is stabilized. Therefore, the optical axis of the laser beam can be stabilized by continuing the optical axis adjustment process during the operation of the laser processing apparatus.

  Next, with reference to the flowchart shown in FIG. 10, the process from the reception of the laser beam to the optical axis adjustment of the optical path adjustment unit 4 in the first optical axis position detector will be described in further detail.

  Step S-10: This step is a control start step. Control for stabilizing the received light intensity in the first optical axis position detecting device to the maximum value is started by an instruction from the operator of the laser processing device or a personal computer.

  Step S-12: This step is a step in which the adjustment value calculation means 26 acquires the output from the first optical axis position detector 10. However, when the amplifier 34 is provided, the adjustment value calculation means 26 obtains the output from the amplifier 34. Hereinafter, for the sake of simplicity, it will be expressed as “output from the first optical axis position detecting device 10”, and when the amplifier 24 is provided, it means the output from the amplifier 24. In this step, the received light intensity acquired by the first optical axis position detection device 10 is measured immediately after the start of control of the optical path of the laser light.

  Step S-14: This step is a step of sequentially driving the motors M1 to M4. An arbitrary motor is selected from the motors M1 to M4 and started. The motor selected first (here, M1) changes the direction of the reflecting surface of the total reflection mirror 22 in FIG. 8 and fixes the rotation of the motor tray at a position where the light receiving intensity becomes maximum. Next, the selected motor (here, M2) similarly changes the direction of the reflecting surface of the total reflection mirror 22, and fixes the rotation of the motor tray at a position where the light receiving intensity is maximized. Similarly, the motors M3 and M4 change the direction of the reflection surface of the second total reflection mirror 24, fix the motor plate at a position where the light receiving intensity becomes maximum, and change the direction of the reflection surface of the second total reflection mirror 24. Fix it.

  The amount of rotation of the motors M1 to M4 for determining the orientation of the reflecting surfaces of the total reflection mirrors 22 and 24 is determined based on fuzzy inference to be described later. The fuzzy reasoning algorithm used here will be described using the rotation amounts of the motors M1 to M4 as parameters by controlling the direction of the reflection surfaces of the total reflection mirrors 22 and 24 described above.

Step S-16: This step is a trial drive step in which rotation drive is performed to determine the rotation direction of the motors M1 to M4.
Step S-18: This step is a step of obtaining a signal proportional to the received light intensity of the laser beam irradiated on the first optical axis position detector 10.

  If it is found in steps S-16 and S-18 described above that the received light intensity received by the first optical axis position detector 10 increases by rotating the motor in a specific direction, the rotation of the motor is performed. Indicates that the received light intensity is in the maximum direction. Conversely, if it is found that the received light intensity received by the first optical axis position detector 10 decreases, this indicates that the rotation of the motor is opposite to the direction in which the received light intensity is maximized.

Step S-20: This step is a step of calculating the time differential value of the output signal of the first optical axis position detector 10 and the amount of deviation from the target value (maximum value). In this step, in fuzzy inference, a time differential (difference) value of the output signal used as an input value is calculated, and a deviation amount from the target value (maximum value) is calculated. Assuming that the value of the output signal from the first optical axis position detector 10 at time t ₁ is s ₁ and the magnitude of the output signal at time t ₂ is s ₂ , it is assumed that t ₁ <t ₂ , The time difference value S ′ of the output signal is given by S ′ = (S ₂ −S ₁ ) / (t ₂ −t ₂ ). Further, when the target value (maximum value) is s ₀ , a deviation amount (ratio of deviation from the target value) ΔS given by ΔS = (s ₁ / s ₀ ) −1 is calculated. Fuzzy inference is performed using S ′ and ΔS.

  Step S-22: This step is a step of calculating the motor drive amount (rotation amount) by fuzzy inference. Although details will be described later, in this step, fuzzy inference is performed using the above-described values of S ′ and ΔS, and the absolute value M of the driving amount (rotation amount) of the motor is calculated.

  Step S-24: This step is a step for obtaining the driving direction (rotation direction) of the motor. If the value of S ′ obtained in step S-20 is negative, it is necessary to reverse the motor driving direction (rotating direction). On the other hand, if the value of S ′ is positive, the rotation direction of the motor may be left as it is. In this step, the rotation direction of the motor described above is obtained by the following procedure. That is, α is a parameter that determines the rotation direction of the motor. α assumes a value 1 or a value -1. The parameter δ is determined as follows. If the value of S ′ obtained in step S-20 is negative, δ = −1, and if the value of S ′ is positive, δ = 1. The next rotation direction of this motor is given by α × δ. That is, by setting this α × δ value as the value of the next new parameter α, the next rotation direction of the motor is determined. When the rotation amount including the rotation direction of the motor is displayed, it is expressed as α × M.

  Step S-26: This step is a step of driving the motor, and the motor is rotated by the above α × M.

  Step S-28: This step is a step of acquiring a signal proportional to the received light intensity irradiated to the first optical axis position detector 10 as in the above-described step S-18.

  Step S-30: In this step, based on the value of the signal proportional to the received light intensity obtained in Step S-28 described above, the adjustment work of the motor controlled and adjusted in the previous steps is completed, and the next step It is determined whether or not to proceed to the step of controlling the motor. The value of the signal proportional to the received light intensity acquired in step S-28 is within a range of values that can be regarded as a target value (maximum value) (a range of values expressed as P sandwiched by arrows in FIG. 9). If it is within the range, the motor to be controlled is switched in order to control the next motor. And it progresses to step S-32 which is the next step. On the other hand, if it is determined that the value of the signal proportional to the received light intensity acquired in step S-28 has not reached the target value, the process returns to step S-20.

  Step S-32: This step is a step of determining whether or not to finish the adjustment work in the optical path adjustment unit 4. If it is confirmed that all the adjustment operations for the motors M1 to M4 have been completed, the process proceeds to the next step S-34 and the adjustment operation is terminated. On the other hand, if the control is continued without ending, the process returns to step S-14. Even if it is confirmed that all the adjustment operations for the motors M1 to M4 are completed, the adjustment operation in the optical path adjustment unit 4 is performed while the laser processing apparatus is being driven in order to cope with the change with time. It may be determined that the process is not terminated.

  Step S-34: This step is a step for ending the adjustment work in the optical path adjustment unit 4.

<Fuzzy reasoning>
With reference to FIGS. 11 (A1) to (A4) and (B1) to (B4) and FIGS. 12 (A1) to (A3) and (B1) to (B3), the light of the laser beam in this laser processing apparatus A membership function used in fuzzy inference executed for axis adjustment will be described. Hereinafter, when referring to all the drawings of FIGS. 11A1 to 11A4 and 11B1 to 4B4, they are simply expressed as FIG. Similarly, when referring to all the drawings in FIGS. 12A1 to 12A3 and 12B1 to B3, it is simply expressed as FIG.

  FIG. 11 is a diagram showing a membership function with respect to a time differential (difference) value S ′ of the output signal detected by the first optical axis position detector 10. FIG. 12 is a diagram showing a membership function for the output signal value ΔS when the target output value of the output signal value of the first optical axis position detector 10 is close to the maximum output value. (A1) to (A4) shown in FIG. 11 indicate the antecedent part of fuzzy inference, and (B1) to (B4) indicate the consequent part corresponding to each of the antecedent parts (A1) to (A4). . Similarly, in FIG. 12, (A1) to (A3) are the antecedent parts of fuzzy inference, and (B1) to (B3) are the antecedent parts of the antecedent parts (A1) to (A3). The subject part is shown.

Even if the optical path adjustment is performed in the optical path adjustment unit 4, the optical axis of the laser light is unstable and a shake of about microradians occurs, and therefore the received light intensity in the first optical axis position detector fluctuates with time. As described above, the temporal change in the received light intensity is observed by the first optical axis position detector 10. The time variation of the received light intensity observed by the first optical axis position detector 10 is the time difference value S ′ of the output signal, that is, S ′ = (s ₂ −s ₁ ) / (t ₂ −t. ₁ ).

  Therefore, the membership function that is the basis of fuzzy inference is defined to follow the following rules (hereinafter sometimes referred to as “fuzzy rules”).

  Rule 11: If S ′ takes a positive value and the value is large, the absolute value of the rotation amount of the motor is large.

  Rule 12: If S ′ takes a positive value and the value is small, the absolute value of the rotation amount of the motor is small.

  Rule 13: If S ′ takes a value of 0, the absolute value of the rotation amount of the motor is 0.

  Rule 14: If S ′ takes a negative value, the absolute value of the rotation amount of the motor is small.

  The above rules will be described visually with reference to FIG. (A1) to (A4) shown in FIG. 11 represent the antecedent parts of the rules 11 to 14 of the above-described fuzzy rule, respectively. In FIGS. 11A1 to 11A4, the horizontal axis indicates S ′, and the vertical axis indicates the degree of matching (having a range of values from 0 to 1). On the other hand, (B1) to (B4) shown in FIG. 11 represent consequent parts of the rules 11 to 14 of the above-described fuzzy rule, respectively. The horizontal axis represents the absolute value M of the driving amount (rotation amount) of the motor, and the vertical axis represents the degree of matching.

Next, when the target output value of the output signal value of the first optical axis position detector 10 is close to the maximum output value, ΔS = (s ₁ / s when the target value (maximum value) is s _{0. The} membership function for ΔS given by ( ₀ ) −1 will be described. Here, s ₁ is the value of the output signal at time t ₁ . There are two reasons why the membership function for ΔS is used.

  First, the first point will be described. Laser light output from the laser light source is a Gaussian beam. Due to the nature of the Gaussian beam, the differential value of the intensity near the center of the beam with respect to the radial direction is small. The differential value in the radial direction of the intensity at a location sufficiently away from the center of the beam is also small. In other words, the optical path adjusting unit 4 performs the alignment of the incident angle of the laser beam on the semi-transparent mirror 8 (spectrometer 44) almost accurately and the case where the alignment is largely deviated. The effect of adjusting the optical path of the laser light is almost the same, and the effect is small. In other words, the first optical axis position detector 10 detects each unit change amount of the direction of the reflecting surfaces of the total reflection mirrors 22 and 24 to be changed in order to adjust the optical path of the laser beam in the optical path adjustment unit 4. The rate of change in received light intensity is as small as that.

  In other words, when the alignment is greatly deviated, the absolute value of the rotation angle of the motor should be set to be large. However, if fuzzy inference is performed using only the above rules 11 to 14, the rotation angle of the motor Is calculated small. Therefore, by setting a new rule for the membership function for ΔS, the magnitude of the rotation angle of the motor can be optimized. However, the target optical system can be adjusted without setting this new rule. However, since the calculated value of the rotation angle of the motor is small, it takes a long time to adjust the optical system to a more optimal state (many control steps).

  Next, the second point will be described. The optical path adjustment function improves the durability against noise by setting the above-described new rule, and there is no problem even if some noise is mixed in the received light intensity detected by the first optical axis position detector 10. However, if only the rules 11 to 14 and no new rule is provided, if noise is mixed in the value of the received light intensity detected by the first optical axis position detector 10, the value of S ′ is unique. Therefore, the value of the rotation angle of the motor may be calculated as an inappropriately large value, and there is a possibility that appropriate control cannot be performed.

  Therefore, if the following new rule is set, the above-described possibility can be eliminated even if noise occurs in the light reception intensity value.

  Therefore, the membership function related to ΔS, which is the basis of fuzzy inference, is defined so as to follow the following fuzzy rule (new rule).

Rule 21: If the received light intensity signal detected by the first optical axis position detector 10 is much smaller than the target value (maximum value) s ₀ (the value of ΔS is a negative value and its absolute value is large). For example, the rotation angle of the motor is large.

Rule 22: The value of almost the same ([Delta] S is the absolute value is smaller negative value signal of the light receiving intensity first optical axis position photodetector 10 detects the relative target value (maximum value) s _0. ), The rotation angle of the motor is small.

Rule 23: If the received light intensity signal detected by the first optical axis position detector 10 has reached or exceeded the target value (maximum value) s ₀ (the value of ΔS is greater than 0), The rotation angle is zero.

  The new rule will be visually described with reference to FIG. (A1) to (A3) shown in FIG. 12 represent the antecedent parts of the rules 21 to 23, respectively, of the above-described fuzzy rule. In (A1) to (A3), the horizontal axis represents ΔS, and the vertical axis represents the degree of matching (having a range of values from 0 to 1). On the other hand, (B1) to (B3) shown in FIG. 12 represent the consequent parts of the rules 21 to 23 of the above-described fuzzy rule, respectively. The horizontal axis represents the absolute value M of the driving amount (rotation amount) of the motor, and the vertical axis represents the degree of matching.

As a method for calculating the driving amount (rotation amount) of the motor by fuzzy inference, the min-max composite centroid method is used here. If the received light intensity is detected by the first optical axis position detector, S ′ and ΔS are obtained based on the values. Now, it is assumed that the values of S ′ and ΔS are obtained as S ′ ₁ and ΔS ₁ .

  FIG. 13 is a diagram for explaining an integration process based on the rules 11 to 14. In FIG. 13, the membership functions corresponding to the rules 11 to 14 are the same as the membership functions shown in FIG.

Since S ′ = S ′ ₁ , in the diagram showing the antecedent part of the membership function corresponding to the rules 11 to 14 shown in FIG. 13, the position corresponding to S ′ ₁ on the horizontal axis representing S ′ is a vertical dotted line Is displayed. As can be seen from this figure, in the above-mentioned rule 13 and rule 14, since the conformity of the antecedent part is 0, the consequent part is also 0. In the rules 11 and 12 described above, since the degree of conformity of the antecedent part is not 0, the membership function of the consequent part is cleaved in accordance with the degree of conformance. As a result, fuzzy inference of the rules 11 to 14 is performed, and as a result of these, the logical sum of the consequent part represented as the integration 1 in FIG. 13 is obtained (integration 1). It should be noted that the function indicating the logical sum of the consequent parts represented as the integration 1 is obtained by synthesizing the membership functions obtained by cutting off the consequent parts of the rules 11 and 12.

  FIG. 14 is a diagram for explaining an integration process based on the rules 21 to 23. In this figure, the membership functions corresponding to the rules 21 to 23 are the same as the membership functions shown in FIG.

Since ΔS = ΔS ₁ , the position corresponding to ΔS ₁ on the horizontal axis representing ΔS is indicated by a vertical dotted line in the diagram showing the antecedent part of the membership function corresponding to the rules 21 to 23 shown in FIG. is there. As can be seen from this figure, since the degree of conformity of the above-mentioned rule 21 is 0, the consequent part is also 0. In the above-described rules 22 and 23, since the conformity of the antecedent part is not 0, the membership function of the consequent part is cleaved in accordance with the conformance. As a result, fuzzy inference of the rules 21 to 23 is performed, and as a result of these, a logical sum of the consequent parts represented as integration 2 in FIG. 14 is obtained (integration 2). It should be noted that the function indicating the logical sum of the consequent part expressed as the integration 2 is a membership function in which the consequent part of the rule 21 and the rule 23 is truncated as in the case of the integration 1 described above. Is obtained by synthesizing.

  Next, how much priority is given to rules 21 to 23 (hereinafter sometimes referred to as “second rule series”) relative to rules 11 to 14 (hereinafter also referred to as “first rule series”), or Processing is performed in consideration of weighting, such as whether the first and second sequences are equally important. The results obtained as the above-described integration 1 and integration 2 (the combined membership function obtained as the logical sum of the consequent parts represented as integration 1 and integration 2 in FIGS. 13 and 14, respectively), The respective functions are weighted by multiplying by r times and (1-r) times, respectively, and as shown in FIGS. 15A to 15D, both are integrated.

  Here, r takes a real value in the range of 0 to 1. For example, selecting r = 1 corresponds to taking only the first rule series and ignoring the second rule series. In addition, selecting r = 0.5 means that the first rule series and the second rule series are handled equally. In addition, selecting r = 0 corresponds to taking only the second rule series and ignoring the first rule series.

  15 (A) to 15 (D) are obtained by integrating the combined membership functions obtained as the logical sum of the consequent parts, which are expressed as integration 1 and integration 2 in FIGS. 13 and 14 described above, respectively. It is a figure where it uses for description of the process which calculates | requires integration 3 as a logical sum of the membership function of integration 1 and integration 2. FIG. FIG. 15A shows a schematic shape of the synthesized membership function obtained as the integration 1, and FIG. 15B shows an outline of the synthesized membership function obtained as the integration 2. Shape. FIG. 15C shows an integration obtained by multiplying the synthesized membership function obtained as integration 1 by r and multiplying the synthesized membership function obtained as integration 2 by (1-r). It is a rough shape of the membership function as the chemical formula 3. FIG. 15D is a diagram for explaining a procedure for obtaining the value of the combined center of gravity of the membership function given in FIG. 15C and adopting the value of the combined center of gravity as the driving amount (rotation angle) of the motor. . In FIG. 15D, the value on the horizontal axis displayed by M and an arrow on the horizontal axis is the position of the composite centroid obtained from the membership function shown in FIG. The position indicates the rotation angle of the motor.

  That is, by performing the above-described fuzzy inference, the rotation angle of the motor that is driven to change the angle of the reflection surface of the total reflection mirror in the optical path adjusting unit 4 can be obtained in order to adjust the optical path of the laser light. I understand.

  In the above description, each rule of the rules 11 to 14 that is the first rule series or each rule of the rules 21 to 23 that is the second rule series has been treated equally. However, emphasis is also placed on these rules. It is also possible to give weight to the degree. In this case, a parameter corresponding to r described above is added to the membership function corresponding to each rule of the rules 11 to 14 as the first rule series or each rule of the rules 21 to 23 as the second rule series. It is sufficient to perform integration by multiplying.

  In the above-described fuzzy inference, the value of the rotation angle of the motor is obtained by using the min-max composite centroid method. However, the present invention is not limited to this method and is known as a fuzzy inference method such as an algebraic product-addition centroid method. Other methods can also be employed. Which method is to be adopted may be the most suitable method based on experience or the like for each laser processing apparatus to be subjected to fuzzy inference control.

  Next, Table 1 and Table 2 summarize the parameters for the first rule series and the second rule series used in the above-described fuzzy inference, respectively. As is clear from the parameters shown in Tables 1 and 2, no particularly complicated fuzzy rules are defined. Nevertheless, it was confirmed that the alignment of the optical system of the laser processing apparatus can be easily realized by executing the control based on the above-described fuzzy reasoning.

  The contents shown in Tables 1 and 2 are mathematically equivalent to those represented by the membership functions shown in FIGS. 11 and 12, respectively. Here, the meanings of the parameters shown in Table 1 and Table 2 are as follows. LP: large positive value, SP: small positive value, ZE: 0, NE: negative value, NS: small negative value, NL: negative value with large absolute value.

From the above description, it can be seen that a so-called origin return operation is not required in the adjustment process of the optical system of the laser processing apparatus according to the present invention. This is because the values used as the basis for the fuzzy inference described above are the time difference value S ′ = (S ₂ −S ₁ ) / (t ₂ −t ₁ ) and the target value of the output signal of the first optical axis position detector. This is because there is only ΔS given by ΔS = (s ₁ / s ₀ ) −1 with respect to (maximum value) S ₀ . That is, in order to obtain the values of S ′ and ΔS, these values are obtained without requiring a so-called home position return operation. As a result, although repeatedly described, even if the optical path adjustment unit 4 is not correctly adjusted according to the control signal from the optical axis control unit 5 due to some cause (for example, backlash), the control signal is sent to the optical path adjustment unit 4 again. As a result, the alignment that satisfies the optimum condition can be completed.

  Further, in the adjustment process of the optical system of the laser processing apparatus according to the present invention, as described above, the adjustment value calculation means 26 uses the optical path for one piece of information of the received light intensity measured by the first optical axis position detector 10. By calculating the corresponding optical path adjustment values at a plurality of adjustment points executed in the adjustment unit 4, it is possible to realize stable fixation of the optical axis position.

  If optical path control is realized without using fuzzy inference, it is necessary to provide error generation processing (routine) and runaway prevention processing (routine) in the alignment work. The amount of program for executing these error generation processing and runaway prevention processing requires the same or more than the processing for the above-described fuzzy inference processing. Further, it is necessary to prepare means for preventing runaway, such as a limiter switch, in the mechanical design of the apparatus. The means for preventing runaway is particularly important in configuring a laser apparatus, and if runaway occurs, it causes serious results such as damage to the workpiece.

  The fuzzy inference program disclosed in the above embodiment is made according to a very simple algorithm. Since it is based on a simple algorithm, it has a structure that makes it difficult for the laser processing apparatus to run out of control due to the nature of the program. In other words, by using fuzzy reasoning, the program can be simplified, and because fuzzy reasoning is used, complex tasks can be performed with simple algorithms.

  Furthermore, performing the process of executing two types of judgments on S ′ and ΔS contributes to suppressing the occurrence of the runaway state. If the alignment operation is to be controlled by judging only one of S ′ and ΔS, the risk of a runaway state increases due to noise mixed in the control signal. When two types of determinations S ′ and ΔS are performed, the device runaway state does not appear unless a factor that causes the runaway state occurs in both S ′ and ΔS. Therefore, by performing the process of executing two types of judgments on S ′ and ΔS, the probability that the runaway state appears can be remarkably reduced.

  As described above, it can be seen that the laser processing apparatus of the present invention has a structure in which a runaway state is unlikely to occur even when viewed as the entire control system.

  As described above, the laser processing apparatus of the present invention adjusts the angle error of the optical axis caused by the fluctuation of the optical axis of the laser light output from the laser light source by fuzzy control, and stabilizes the position of the optical axis of the laser light. Can be fixed.

Schematic diagram of the overall configuration of the laser processing apparatus 1 according to the present invention having nano unit precision Embodiment in which the irradiation point of laser light is completely irradiated with only one pixel as a reference pixel among light receiving pixels arranged in a matrix in the first optical axis position detector Embodiment in which the irradiation point of laser light uniformly irradiates a part of four pixels forming a four quadrant sensor among light receiving pixels arranged in a matrix in the first optical axis position detector Modified embodiment regarding arrangement of light receiving elements in first optical axis position detector 10 A modified embodiment in which the position of the optical axis of the laser beam is detected using the first optical axis position detector and the second optical axis position detector Modified embodiment of FIG. 1 is an enlarged view showing a state in which a pinhole 72 supported by a support base 71 is disposed between the condenser lens 9 and the first optical axis position detector 10 in FIG. Schematic block configuration for explaining an optical path adjustment function of a laser processing apparatus according to the present invention Diagram for explaining changes in received light intensity Flow chart showing optical path adjustment step based on fuzzy inference Diagram showing membership function for S ' Diagram showing membership function for ΔS Diagram for explaining the integration process based on rules 11-14 Diagram for explaining the integration process based on rules 21 to 23 Diagram for explaining the process of obtaining integration 3 as the logical sum of the integration functions of integration 1 and integration 2

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus by this invention 2 Laser light source 3 Anti-vibration table 4 Optical path adjustment part 5 Optical axis control part 6 Movable stand 7 Stage 8 Semi-transparent mirror 9 Condensing lens 9 'Condensing lens 10 1st optical axis position detector 11 Covered Workpiece 12 Movable stand position detector 13 Total reflection mirror 15 Second optical axis position detector 16 Second semi-transmission mirror 18 Second total reflection mirror 20 Laser light irradiation point 21 CCD pixel 22 Total reflection mirror 24 Total reflection mirror 26 Calculation Means 28 Motor control unit 30 Laser light irradiation point A Inter-pixel distance S1 to S4 Laser light irradiation area 40 in pixel 4 array plane of four pixels (four quadrants) 41 Laser light reflecting sphere 42 Pinhole 50 Mirror support base
71 Pinhole support 72 Pinhole

Claims (5)

A light source that outputs laser light;
An optical path adjustment unit for adjusting the optical path of the laser beam;
A first spectroscope for splitting laser light;
A movable table having a predetermined range of motion on which a workpiece is placed;
A movable table position detector for detecting the position of the movable table;
A first optical axis position detector for detecting the position of the optical axis of the split laser beam;
A stage on which the movable table, the movable table position detector, and the first optical axis position detector are mounted;
An optical axis control unit that receives the output from the first optical axis position detector and controls the optical path adjustment unit, and adjusts the optical axis of the dispersed laser beam;
A laser processing apparatus comprising:   The laser processing apparatus according to claim 1, wherein the optical axis control unit performs fuzzy control.   A first optical axis position detector, further comprising: a second spectroscope for further splitting the split laser light; and a second optical axis position detector for detecting the position of the optical axis split by the second spectrometer. 3. The laser processing apparatus according to claim 1, wherein the optical axis control unit is controlled such that the laser beam is detected at a predetermined position by the detector and the second optical axis position detector.   At least one of the first optical axis position detector and the second optical axis position detector is configured such that the laser beam dispersed by the first spectrometer or the laser beam dispersed by the second spectrometer is reflected on the spherical reflecting surface. 4. The laser processing apparatus according to claim 1, wherein the position of the optical axis of each laser beam is detected by receiving light with a four-quadrant sensor.   A predetermined aperture for allowing laser light to pass between the first spectrometer and the first optical axis position detector, or at least one of the second spectrometer and the second optical axis position detector. 5. The laser processing apparatus according to claim 1, wherein a pinhole having a surface is disposed.

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