Method and device for adjusting an optical axis of laser light

Abstract

A method and a device for adjusting an optical axis of laser light are provided, capable of accurately detecting changes in the state of the laser light and maintaining the quality of laser processing. The method for adjusting an optical axis of laser light comprises: a step of detecting the position of the laser light by position-sensitive detectors arranged at two or more detection positions in an optical path of the laser light emitted from a laser light source towards a workpiece; and a step of adjusting, based on the detected position of the laser light, a position and / or angle of optical elements arranged at two or more positions in the optical path of the laser light to adjust an optical axis of the laser light.

Description

Background of the inventionField of the invention

[0001] The present invention relates to a method and an apparatus for adjusting an optical axis of laser light, and more particularly relates to a technique for adjusting the optical axis of laser light in a laser processing apparatus. Description of the state of the art

[0002] A laser processing device (also called a laser cutting device) is known that irradiates a workpiece, such as a semiconductor wafer, with laser light to form a processing groove or laser-modified areas (laser processing area) that serve as the starting point for cutting inside the workpiece. After laser processing, the semiconductor wafer is separated (cut) into individual chips along planned separation lines using a cleaving process, such as expanding, braking, or breaking.

[0003] When the state of the laser light in the laser processing device changes from the state at the completion of adjustment, a beam profile of the laser light at a processing point may change, so that the machining result of the workpiece may change due to the influence of the change in the beam profile. Patent Literatures 1 and 2 disclose methods for detecting such changes in the state of the laser light.

[0004] Patent Literature 1 discloses a method for detecting a position of a laser beam at a machining point after passing through a condenser lens and adjusting an optical axis of the laser beam.

[0005] Patent Literature 2 discloses a system that detects the position of a reflection spot of laser light in a laser gain medium that emits fluorescent light when absorbing a part of the excitation light, and controls the angle or position of an optical element to adjust an optical axis of the laser light. List of cited publicationsPatent literature Patent Literature 1: Japanese Patent Application Laid-Open No. 2020-189323 Patent Literature 2: Japanese Patent Application Laid-Open No. 2017-022351 Overview of the invention

[0006] The methods disclosed in Patent Documents 1 and 2 detect a beam position at the machining location irradiated with laser light, making it difficult to accurately detect the change in the state of the laser light as described below.

[0007] As in Fig. As shown in Figure 17, when detecting laser light that has passed through an optical element OE (e.g., a condenser lens, etc.) at a detection position OP, there are countless optical axes passing through the detection position OP. These countless optical axes passing through the one detection position OP differ from each other in the incident position and the angle of incidence on the optical element OE. These optical axes are also inclined with respect to lines parallel to an optical axis of the optical element OE (solid lines in Fig. 17, which are vertical lines when the optical element OE is rectangular).

[0008] Therefore, it is not possible to accurately detect the incident position and angle of the laser light incident on the optical element by only detecting the beam position at the processing point as in Patent Documents 1 and 2. Furthermore, the techniques disclosed in Patent Documents 1 and 2 cannot accurately detect the deviation of the reflection angle of a mirror serving as an optical element from a design value.

[0009] Furthermore, the technique disclosed in Patent Literature 1 aims to reduce the man-hours required for adjusting the optical axis of the laser beam. The method described in Patent Literature 2 aims to eliminate the need for a reference laser light source used to adjust the optical axis of a laser. In other words, since both the techniques disclosed in Patent Literature 1 and 2 do not consider monitoring the optical axis deviation of the laser light to maintain the beam profile, it is difficult to maintain the quality of laser processing.

[0010] The present invention has been conceived in view of such circumstances and aims to provide a method and an apparatus for adjusting an optical axis of laser light capable of accurately detecting changes in the state of laser light and maintaining the quality of laser processing.

[0011] To achieve the above object, a method for adjusting an optical axis of laser light according to a first aspect of the present invention includes: a step of detecting a position of laser light by position-sensitive detectors arranged at two or more detection positions in an optical path of laser light output from a laser light source toward a workpiece; and a step of adjusting, based on the position of the laser light, at least a position and an angle of at least two optical elements in the optical path of the laser light to adjust the optical axis of the laser light.

[0012] According to a second aspect of the present invention, in the method for adjusting an optical axis of the laser light according to the first aspect, the detection positions are provided at positions other than a processing point to be irradiated with the laser light on the workpiece.

[0013] According to a third aspect of the present invention, in the method for adjusting an optical axis of the laser light according to the first or second aspect, adjustment of the optical axis of the laser light is performed when a difference between the position of the laser light detected by the position-sensitive detectors arranged at two or more detection positions and a preset reference value is equal to or larger than a threshold value.

[0014] According to a fourth aspect of the present invention, the method for adjusting an optical axis of laser light according to any one of the first to third aspects includes a step of adjusting the optical axis by a beam expander retractably arranged in the optical path of the laser light.

[0015] According to a fifth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the fourth aspect, the position of the laser light in a state where the magnification of the beam expander is set to 1x is adjusted according to the position of the laser light in a state where the beam expander is retracted from the optical path of the laser light.

[0016] An apparatus for adjusting an optical axis of laser light according to a sixth aspect of the present invention comprises: position-sensitive detectors arranged at two or more detection positions on an optical path of laser light output from a laser light source toward a workpiece; and an adjustment mechanism configured to adjust at least a position and an angle of optical elements at two or more positions on the optical path of the laser light based on a position of the laser light detected by the position-sensitive detectors, to adjust the optical axis of the laser light.

[0017] A method for adjusting an optical axis of laser light according to a seventh aspect of the present invention includes: a step of detecting a position of laser light output from a laser light source toward a workpiece using two paired position-sensitive detectors arranged at positions respectively after the laser light passes through two paired half mirrors, the two half mirrors being fixed to an upstream side and a downstream side of a beam expander; and a step of adjusting, based on the position of the laser light, at least a position and an angle of two paired movable mirrors arranged closer to the laser light source than the two half mirrors in an optical path of the laser light to adjust an optical axis of the laser light.

[0018] According to an eighth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the seventh aspect, the two position-sensitive detectors are provided at a position other than a processing point to be irradiated with the laser light on the workpiece.

[0019] According to a ninth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the seventh or eighth aspect, adjustment of the optical axis of the laser light is performed when a difference between the position of the laser light detected by the two position-sensitive detectors and a preset reference value is equal to or greater than a threshold value.

[0020] According to a tenth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the ninth aspect, adjusting the position and / or angle of one of the two movable mirrors and setting the position of the laser light detected by one of the two position-sensitive detectors as a reference value are repeated for each of the movable mirrors to merge the position of the laser light detected by each position-sensitive detector with the respective reference position.

[0021] An optical axis adjusting device for laser light according to an eleventh aspect of the present invention comprises: two paired position-sensitive detectors arranged respectively at positions after the laser light has passed through two paired half mirrors, the half mirrors being respectively fixed to an upstream side and a downstream side of a beam expander; and an adjusting mechanism configured to adjust at least a position and an angle of two paired movable mirrors, arranged closer to a laser light source than the two half mirrors on an optical path of the laser light, based on the position of the laser light detected by each of the position-sensitive detectors, to adjust an optical axis of the laser light.

[0022] A method for adjusting an optical axis of laser light according to a twelfth aspect of the present invention includes: a step of detecting a position of laser light output from a laser light source toward a workpiece using position-sensitive detectors each disposed on an upstream side and a downstream side of a beam expander; and a step of moving the beam expander to adjust an optical axis of the laser light based on the position of the laser light detected by the position-sensitive detectors in a state where the beam expander is disposed on an optical path of the laser light and the position of the laser light detected by the position-sensitive detectors in a state where the beam expander is retracted from the optical path of the laser light.

[0023] According to a thirteenth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the twelfth aspect, in adjusting the optical axis, the position of the laser light in a state where the magnification of the beam expander is set to 1x is adjusted according to the position of the laser light in the state where the beam expander is retracted from the optical path of the laser light.

[0024] According to a fourteenth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the twelfth or thirteenth aspect, in adjusting the optical axis, the position of the laser light in a state where the magnification of the beam expander is set to a value other than 1x or 1x is adjusted in accordance with the position of the laser light in the state where the beam expander is retracted from the optical path of the laser light.

[0025] According to a fifteenth aspect of the present invention, the method for adjusting an optical axis of laser light according to the twelfth or thirteenth aspect includes a step of performing a quality determination for the beam expander based on a change in the position of the laser light detected by the position-sensitive detectors when the magnification of the beam expander is changed.

[0026] According to a sixteenth aspect of the present invention, in the method for adjusting an optical axis of laser light according to the fifteenth aspect, in the step of performing the quality determination, the quality of the beam expander is determined to be good when a movement amount of the position of the laser light detected by the position sensitive detectors is equal to or smaller than a reference value, or the position of the laser light changes linearly in accordance with a change in the magnification of the beam expander.

[0027] An apparatus for adjusting an optical axis of laser light according to a seventeenth aspect of the present invention comprises: a beam expander retractably disposed in an optical path of laser light output from a laser light source to a workpiece; position-sensitive detectors disposed on an upstream side and a downstream side of the beam expander; and an adjusting mechanism configured to move the beam expander to adjust an optical axis of the laser light based on a position of the laser light detected by the position-sensitive detectors in a state where the beam expander is disposed in the optical path of the laser light and a position of the laser light detected by the position-sensitive detectors in a state where the beam expander is retracted from the optical path of the laser light.

[0028] A quality determination method of a beam expander according to an eighteenth aspect of the present invention includes: a step of detecting a position of laser light output from a laser light source toward a workpiece using position-sensitive detectors arranged on an upstream side and a downstream side of a beam expander; and a step of making a pass or fail determination for the beam expander based on a change in the irradiation position of the laser light detected by the position-sensitive detectors when the magnification of the beam expander is varied in a state where the beam expander is arranged in an optical path of the laser light.

[0029] According to a nineteenth aspect of the present invention, in the quality determination method of a beam expander according to the eighteenth aspect, in the step of performing the quality determination, the quality of the beam expander is determined to be good when a movement amount of the position of the laser light detected by the position sensitive detectors is equal to or smaller than a reference value, or the irradiation position of the laser light changes linearly in accordance with the change in the magnification of the beam expander.

[0030] According to the present invention, the position of an optical axis of the laser light L1 is detected at two or more detection positions, thereby limiting the optical axis of the laser light L1 to one. This makes it possible to accurately detect changes in the state of the laser light and maintain the quality of laser processing. Brief description of the drawings Fig. 1 is a diagram for describing a method and apparatus for adjusting an optical axis of laser light according to a first embodiment of the present invention. Fig. 2 is a block diagram showing a laser processing apparatus according to the first embodiment of the present invention. Fig. 3 is a block diagram showing an example of an illumination optical system. Fig. 4 is a diagram for describing a determination condition for determining whether or not to perform optical axis correction of laser light. Fig. 5 is a diagram for describing a correction direction of the optical axis of the laser light. Fig. 6 is a diagram showing the result of optical axis adjustment. The Fig. 7A and Fig. 7B are diagrams showing the result of adjusting the optical axis in a rolling direction. Fig. Figure 8 is a diagram illustrating the influence on a beam profile at a machining point when the incident position on an optical element deviates. Fig. 9 is a flowchart (Example 1) showing a method of correcting an optical axis according to the first embodiment of the present invention. Fig. 10 is a flowchart (Example 2) showing the optical axis correction method according to the first embodiment of the present invention. Fig. 11 is a flowchart showing an optical axis adjustment method according to a second embodiment. Fig. 12 is a flowchart showing the optical axis adjustment method according to the second embodiment. The Fig. 13A and Fig. 13B shows the results of detecting the laser light before and after adjusting the position of a beam expander. Fig. 14 is a flowchart showing a first example of a quality determination method for the beam expander. Fig. Figure 15 is a flowchart showing a second example of the quality determination procedure for the beam expander. Fig. 16 is a block diagram showing an example of the illumination optical system in a fourth embodiment of the present invention. Fig. 17 is a diagram showing an example of detecting the position of the laser light at a detection position. Description of the embodiments

[0031] Embodiments of a method and an apparatus for adjusting an optical axis of laser light according to the present invention will be described below with reference to the accompanying drawings. [First embodiment]

[0032] (Overview of a method and apparatus for adjusting an optical axis of laser light)

[0033] Fig. 1 is a diagram for describing a method and apparatus for adjusting an optical axis of laser light according to a first embodiment of the present invention.

[0034] As in Fig. As shown in Figure 1, a system according to the present embodiment includes a unit that detects laser light (laser beam) output from a laser light source of a laser processing device at two or more detection positions that are not processing points and determines whether the position of the optical axis of the laser light is normal or not. Fig. In the example shown in Figure 1, the position of the optical axis of the laser light can be detected at two detection positions OP1 and OP2 provided on an upstream side and an upstream side of an optical element OE, respectively.

[0035] Furthermore, the system according to the present embodiment includes an adjustment mechanism that adjusts a position or angle of an optical element holder holding the optical element OE in accordance with a determination result regarding the position of the optical axis of the laser light. The optical element holder, which is adjustable by the adjustment mechanism, may be provided, for example, at two or more positions in the optical path of the laser light.

[0036] The system according to the present embodiment can limit the optical axes of the laser light to exactly one by detecting the laser light at two or more detection positions. As a result, the incident position and angle of the laser light incident on the optical element OE can be appropriately adjusted. For example, the reflection angle of a mirror can be adjusted accordingly.

[0037] In the Fig. In the example shown in Figure 1, the detection positions (OP1 and OP2) are two or more positions other than the machining point, although the present invention is not limited to this configuration. For example, two or more detection positions (OP1 and OP2) may include a machining point, which is a position to be irradiated with laser light (irradiation position) on a workpiece. (Laser processing device)

[0038] Hereinafter, a method and an apparatus for adjusting an optical axis of laser light according to the present embodiment will be described in detail.

[0039] First, an example of a laser processing apparatus will be described with reference to Fig. 2 described. Fig. 2 is a block diagram showing the laser processing apparatus according to the first embodiment of the present invention.

[0040] As in Fig. 2, a laser processing apparatus 10 includes a table 12 that moves a workpiece W (e.g., a semiconductor wafer), a laser irradiation device 20 that irradiates the workpiece W with laser light, and a control unit 50 that controls each unit of the laser processing apparatus 10.

[0041] In the following, a three-dimensional orthogonal coordinate system is used in which the table 12 is parallel to the XY directions and perpendicular to a Z direction.

[0042] The table 12 is configured to be movable in the X, Y, Z, and θ directions. The table 12 suctions and holds the workpiece W. A back grinding belt (hereinafter referred to as BG belt) with adhesives is adhered to the front surface of the workpiece W, on which components are formed. The workpiece W is mounted on the table 12 with its back side facing upward in the drawing. Hereinafter, the surface of the workpiece W on the side of a condenser lens 24 is referred to as a laser light irradiation surface.

[0043] Here, the laser light irradiation surface may be the surface (back surface) opposite to the condenser lens 24 side surface of the workpiece W. The workpiece W may have a cutting film with adhesives adhered to one surface, and may be mounted on the table 12 in the state of being integrated into a frame by the adhesive film.

[0044] The laser irradiation device 20, which is arranged at a position facing the workpiece W, irradiates the workpiece W with processing laser light L1 to form laser-modified regions in the workpiece W (e.g., inside the workpiece W, etc.).

[0045] The control unit 50 has a central processing unit (CPU), a memory, a storage device, input / output circuits, and the like for storing, for example, data required for the operation of each unit of the laser processing apparatus 10 or for processing. In addition, the laser processing apparatus 10 has wafer transfer means, an operation panel, a monitor, an indicator light, and the like, which are not shown.

[0046] The control panel is equipped with switches and indicators for controlling the motion of the individual units of the laser processing device 10. A TV monitor displays wafer images captured by a CCD (charge-coupled device) camera (not shown), or displays program contents and various types of messages. The indicator light indicates the operating status of the laser processing device 10, e.g., during processing, after processing completion, or during an emergency stop.

[0047] The detailed structure of the laser irradiation device 20 is described below. As shown in Fig. 2, the laser irradiation device 20 includes a laser light source 21, an illumination optical system 22, a dichroic mirror 23, the condenser lens 24, an actuator 25, and an AF device 30.

[0048] The laser light source 21 emits the processing laser light (hereinafter also referred to as laser light) L1 to form laser-modified regions inside the workpiece W. The laser light source 21 emits, for example, laser light with a pulse width of 1 µs or less and a peak power density of 1 × 10 8 (W / cm 2 ) or more at one focal point.

[0049] The illumination optical system 22, the dichroic mirror 23, and the condenser lens 24 are arranged in a first optical path of the processing laser light L1 in this order from the laser light source 21. The dichroic mirror 23 transmits the processing laser light L1 and reflects the AF laser light L2 emitted from the AF device 30. Note that a second optical path of the AF laser light L2 is curved by the dichroic mirror 23 to share a part of the optical path with the first optical path of the processing laser light L1, and the condenser lens 24 is arranged on the common optical path.

[0050] The processing laser light L1 emitted from the laser light source 21 passes through the illumination optical system 22 and the dichroic mirror 23 and is then focused onto the workpiece W by the condenser lens 24. The condenser lens 24 is finely moved in the Z direction by the actuator 25 to adjust the position of a focal point of the processing laser light L1 in the Z direction (in the wafer thickness direction).

[0051] Upon receiving reflected light of the AF laser light L2 irradiated onto the workpiece W, the AF device 30 outputs information (distance information) about the distance between the condenser lens 24 and the laser light irradiation surface of the workpiece W to the control unit 50.

[0052] The control unit 50 controls the drive of the actuator 25 to maintain a prescribed ratio of the distance between the condenser lens 24 and the laser light irradiation surface of the workpiece W (to maintain a constant distance). (Optical illumination system)

[0053] An example of an optical illumination system 22 is described below with reference to Fig. 3 described. Fig. 3 is a block diagram showing an example of an illumination optical system.

[0054] Fig. 3 shows the optical path of the laser light L1 from a laser head LH of the laser light source 21 to the workpiece W. It should be noted that the dichroic mirror 23 in Fig. 3 is omitted.

[0055] The laser head LH contains a condenser lens that collects the laser light L1 emitted by a laser oscillator of the laser light source 21. The laser head LH emits the collimated laser light L1 onto the workpiece W. The laser light L1 is successively reflected by the mirrors M1 to M3 and a half mirror M4 and radiated toward an attenuator ATN.

[0056] A beam shutter BS controls the exit of the laser light L1 to a downstream side (side of the mirror M4) in accordance with the control of the control unit 50.

[0057] Mirrors M1 and M3 (an example of a pair of movable mirrors) are held by holders H1 and H3, respectively. Holders H1 and H3 are attached to gimbals, for example. Mirrors M1 and M3 are steering mirrors with an adjustment mechanism 52 (e.g., an actuator). Adjustment mechanism 52 rotates holders H1 and H3 about their respective rotation axes under the control of control unit 50 to adjust an irradiation position and irradiation angle of laser light L1.

[0058] After the laser light L1 is attenuated to an appropriate level (amplitude) by the attenuator ATN, the beam diameter of the laser light L1 is expanded by a beam expander BE, and the laser light L1 is formed into collimated light (parallel light). Then, the laser light L1 passes through optical elements, such as a half mirror M5, a mirror M6, a relay lens LZ1, a mirror M7, a relay lens LZ2, a mirror M8, and a half mirror M9, and is focused onto the workpiece W by the condenser lens 24.

[0059] As in Fig. As shown in Figure 3, the position-sensitive detectors PSD1 and PSD2 (example of two position-sensitive detectors as a pair) are each arranged on the downstream side of the half-mirrors M4 and M5 (example of two half-mirrors (fixed mirrors) provided as a pair).

[0060] The position-sensitive detectors PSD1 and PSD2, which contain a photodiode, are sensors that use the surface resistance of the photodiode to detect the incident position of the laser light L1. The position-sensitive detectors PSD1 and PSD2 each detect the incident position of the laser light L1 that has passed through the half mirrors M4 and M5. Fig. In the example shown in Figure 3, the incident positions of the laser light L1 for the respective locations or positions are designated by the reference numbers A1 and A2.

[0061] The device for adjusting an optical axis of laser light according to the present invention comprises the position-sensitive detectors PSD1 and PSD2 and the adjusting mechanism 52 for the mirrors M1 and M3.

[0062] Position-sensitive detectors PSD1 and PSD2 can be sensors that detect the incident position of the laser light L1 with an imaging element.

[0063] A laser scanning microscope LSM detects an irradiation position of the laser light L1 on the laser light irradiation surface of the workpiece W. For example, the laser scanning microscope LSM detects the irradiation position of the laser light L1 at any time during laser processing through the half mirror M9, thus monitoring the state of laser processing.

[0064] The number and arrangement of the position-sensitive detectors PSD1 and PSD2 is not limited to the Fig. 3. The number and arrangement of the steering mirrors is also not limited to the Fig. 3. Mirrors other than mirrors M1 and M3 can also be used as steering mirrors.

[0065] In the present embodiment, the adjustment of the optical axis is performed by adjusting at least two mirrors M1 and M3, although the adjustment of the optical axis may also be performed by adjusting at least one of the positions and angles of optical elements other than mirrors (e.g., lenses, prisms, etc.). (Example of optical axis correction)

[0066] The following describes the method for correcting an optical axis of the laser light L1 using the two position-sensitive detectors PSD1 and PSD2.

[0067] In the present embodiment, the positions A1 and A2 of the laser light L1 are detected using two position-sensitive detectors PSD1 and PSD2. Depending on whether the positions A1 and A2 deviate from an allowable range, the holders H1 and H3, which hold the respective mirrors M1 and M3, are driven to correct the optical axis.

[0068] Fig. Fig. 4 is a diagram for describing a determination condition for determining whether or not to perform a correction operation of the optical axis of the laser light, and Fig. 5 is a diagram for describing a correction direction of the optical axis of the laser light.

[0069] In the present embodiment, first, the position-sensitive detectors PSD1 and PSD2 are used to detect the irradiation position of the laser light L1 at the time when the adjustment of the laser light in the laser irradiation device 20 is completed, and the detected irradiation position of the laser light L1 is used as a reference position (reference value). In addition, a threshold value for determining the optical axis deviation is set. Fig. In the example shown in Figure 4, the reference value is (x0, y0) and the threshold value is rth.

[0070] When the laser irradiation device 20 is operating (for example, before and after laser processing and during laser processing), the position-sensitive detectors PSD1 and PSD2 are used to detect the irradiation position of the laser light L1. When a difference r between the position (actual value) of the laser light L1 and the reference value exceeds the threshold value rth, the steering mirrors M1 and M3 are controlled to adjust the optical axis of the laser light L1. The difference r between the actual value of the laser light L1 and the reference value is expressed by Formula 1 below. r=(x−x0)2+(y−y0)2

[0071] In the Fig. In the example shown in Figure 4, a circle Cth with a radius rth and the reference value (x0, y0) as its center is shown. If the actual values ​​of the laser light L1 detected by the position-sensitive detectors PSD1 and PSD2 both lie within the circle Cth (when the actual value 1 is equal to (x1, y1) and r1 < rth), the optical axis adjustment is not performed.

[0072] On the other hand, when the actual values ​​of the laser light L1 detected by the position sensitive detectors PSD1 and PSD2 are outside the circle Cth (when the actual value 2 is equal to (x2, y2) and r2 > rth), the optical axis adjustment is performed.

[0073] Here, an adjustment amount for the optical axis (xoff, yoff) can be determined based on the difference between the actual value and the reference value. More specifically: (xoff,yoff)={(x−x0),(y−y0)}.

[0074] A setting direction or adjustment direction (movement direction) of the optical axis is as follows (see Fig. 5). - If xoff < 0, the optical axis moves in a positive (+) direction of the x-direction. - If xoff > 0, the optical axis moves in a negative (-) direction of the x-direction. - When yoff < 0, the optical axis moves in a positive (+) direction of the y-direction. - When yoff > 0, the optical axis moves in a negative (-) direction of the y-direction.

[0075] Once the optical axis adjustment is completed, the position-sensitive detectors PSD1 and PSD2 can be used to re-detect the irradiation position of the laser light L1 and confirm the optical axis adjustment result. Furthermore, a power meter (not shown) can be used to check the laser power (e.g., an attenuation amount) on the upstream side of the condenser lens 24 or at the machining point of the workpiece W, and the optical axis adjustment result can be confirmed based on the inspection result.

[0076] Fig. 6 is a diagram showing the result of optical axis adjustment. Fig. Figure 6 illustrates the detection result of the laser light L1 by the position-sensitive detector PSD1 arranged in a cross pattern, in a case where the mirror M1 is moved every 100 pulses in the roll and pitch directions based on the reference position (image center, (roll direction, pitch direction) = (0, 0)). Here, the roll direction is the direction around the axis in a moving direction (optical axis direction) of the laser light L1, and the pitch direction is the direction around the axis in a direction perpendicular to the moving direction. Fig. 6, the units of the amount of movement of the mirrors M1 and M3 (steering mirrors) are expressed in pulses. The displacement corresponding to one pulse is approximately 1 µm.

[0077] The picture in the middle of Fig. 6 ((Roll direction, Pitch direction) = (0, 0)) is the result of the detection of the laser light L1 by the position-sensitive detector PSD1 when the mirrors M1 and M3 are both in the reference position. In the middle image of Fig. 6, a light beam extending crosswise from laser light L1 is approximately equal in an up-down direction and a right-left direction. Note that the shape and number of light beams emanating from laser light L1 may vary depending on the composition of the optical element in the illumination optical system 22.

[0078] When the mirror M1 is moved in the rolling direction relative to the reference position, the more the mirror M1 is moved to the positive (+) side, the more the cross-shaped light beam is shifted to the right in the drawing, and the more the mirror M1 is moved to the negative (-) side, the more the cross-shaped light beam is shifted to the left in the drawing, as shown in a partially enlarged view in Fig. 6 is shown.

[0079] In the present embodiment, when a deviation from the reference position is detected, the control unit 50 first controls the mirror M1 so that the detection result of the laser light L1 by the position-sensitive detector PSD1 becomes equal to the reference position. Next, the control unit 50 controls the mirror M3 so that the detection result of the laser light L1 by the position-sensitive detector PSD2 becomes equal to the reference position. Thereafter, the control of the mirrors M1 and M3 is repeated sequentially to adjust the position of the laser light L1 to the reference position.

[0080] The Fig. 7A and Fig. 7B are diagrams illustrating the result of adjusting the optical axis in the rolling direction. Fig. Figure 7A shows the result of the optical axis adjustment when the mirror M1 is moved by +500 pulses in the rolling direction, and Fig. Figure 7B shows the optical axis adjustment result when mirror M1 is moved by +300 pulses in the roll direction. Each graph shows the change in the deviation amounts (amounts of deviation) of mirrors M1 and M3 (µm) from the reference position over time when mirrors M1 and M3 are repeatedly moved.

[0081] As in the Fig. 7A and Fig. As shown in Figure 7B, it can be seen that the deviations from the reference position due to the repeated driving of the mirrors M1 and M3 converge in the two cases where the movement amount of the mirror M1 is +500 pulses and +300 pulses. This shows that when the movement amount from the reference position (i.e., the sum of an assumed position change amount (deviation amount) of the mirror (M1 or M3) and a margin) is approximately 500 µm, the correction operation can be performed by adjusting the optical axis. Note that similar correction can also be performed in the pitch and yaw directions.

[0082] Fig. Figure 8 is a diagram illustrating the influence on a beam profile at the machining point when the incident position on an optical element deviates. Fig. Figure 8 shows the beam profile at the machining point when the amount of deviation from the reference position is 0 to 500 µm. A horizontal axis in Fig. 8 represents the pixels of an imaging element of the laser scanning microscope LSM, and a vertical axis represents the intensity of the laser light L1.

[0083] From the Fig. From the example shown in Figure 8, it can be seen that the shape of a beam profile curve at the machining point varies with the change in the amount of deviation from the reference position.

[0084] The present embodiment can reduce the fluctuation of the beam profile as shown in Fig. 8, by detecting the position of the laser light L1 at two or more positions in the optical path of the laser light L1 and controlling the mirrors M1 and M3 so that the amount of deviation from the reference position decreases (disappears). (Optical axis correction method (Example 1))

[0085] A method for correcting the optical axis according to the present embodiment will be described below.

[0086] Fig. 9 is a flowchart (Example 1) showing the optical axis correction method according to the first embodiment of the present invention. Fig. 9 shows an example in which the optical axis correction is performed at the start of the system of the laser processing apparatus 10 or manually.

[0087] When the laser processing device 10 is activated (step S10) and initialized (step S12), a laser idle state is first established (step S14). The laser idle state is the state in which the laser light L1 is emitted toward a processing point on the workpiece W.

[0088] Next, the irradiation position of the laser light L1 is detected using the position-sensitive detectors PSD1 and PSD2 (step S16), and the directions of the mirrors M1 and M3 (steering mirrors) are corrected (step S18). Then, as shown in Fig. 4, the correction of the directions of the mirrors M1 and M3 is repeated until the irradiation position (actual value) of the laser light L1 coincides with the reference value or the difference r from the reference value becomes equal to or smaller than the threshold value rth.

[0089] Here, the threshold value during the optical axis adjustment (step S16) at the start-up of the system may be smaller than the threshold value rth at the time of determining the need for optical axis adjustment in Fig. 4.

[0090] When the correction of the direction of the mirrors M1 and M3 is completed (steps S14 to S18), the laser power on the upstream side of the condenser lens 24 or at the processing point of the workpiece W is confirmed by a power meter (step S20), and the irradiation position (processing point) of the laser light L1 is confirmed by the laser scanning microscope LSM (step S22), and then the laser processing is performed (step S24). (Optical axis correction method (Example 2))

[0091] Fig. 10 is a flowchart (Example 2) showing the optical axis correction method according to the first embodiment of the present invention. Fig. 10 shows a case where the optical axis correction is performed during the execution of laser processing by the laser processing apparatus 10.

[0092] When laser machining is performed, a machining position confirmation is first performed before the machining operation. In a case of performing the machining position confirmation (step S30), as shown in Fig. As shown in Figure 4, OK is determined when the difference r between the irradiation position (actual value) of the laser light L1 and the reference value is equal to or less than the threshold value rth, and NG is determined when the difference r exceeds the threshold value rth. Then, if OK is determined in step S30, the flow proceeds to the processing operation without executing the optical axis adjustment. On the other hand, if NG is determined in step S30, the optical axis adjustment is executed (steps S52 to S56).

[0093] When adjusting the optical axis, a laser idle state is first established (step S52), the irradiation position of the laser light L1 is detected with the position-sensitive detectors PSD1 and PSD2 (step S54), and the direction of the mirrors M1 and M3 (steering mirrors) is corrected (step S56). Then, the correction of the direction of the mirrors M1 and M3 is repeated until the irradiation position (actual value) of the laser light L1 coincides with the reference value or the difference r from the reference value is equal to or smaller than the threshold value rth. Note that the threshold value at the time of adjusting the optical axis in step S54 may be smaller than the threshold value rth at the time of determining the need for optical axis adjustment in steps S30 and S50 described later.

[0094] Once the direction correction of mirrors M1 and M3 is completed (steps S52 to S56), the flow proceeds to the machining process. Before the machining process, a power check and a check of the irradiation position (machining point) of laser light L1 can be performed.

[0095] The optical axis adjustment before starting the machining process will be described next. In this case, the irradiation position of the laser light L1, detected by the position-sensitive detectors PSD1 and PSD2, is detected during the execution of the previous machining process (step S50), and the necessity of optical axis adjustment is determined in the same manner as in step S30. Then, if OK is determined in step S50, the flow proceeds to the processing process without executing the optical axis adjustment. On the other hand, if NG is determined in step S50, the optical axis adjustment is executed (steps S52 to S56).

[0096] The process performed after the end of the machining process will now be described, e.g., after the machining process for a certain number of planned parting lines is completed and before the machining process for the next planned parting lines begins. After the end of the machining process, a kerf inspection (kerf control) for the kerf formed by laser machining (step S70) and a check of the irradiation position of the laser light L1 (step S72) are first performed by the laser scanning microscope LSM.

[0097] If both steps S70 and S72 are determined to be OK, the flow proceeds to the next processing operation. If both steps S70 and S72 are determined to be NG, the irradiation position of the laser light L1 detected by the position-sensitive detectors PSD1 and PSD2 during the execution of the previous processing operation is detected (step S74), and the need for optical axis adjustment is determined in the same manner as in step S50. Note that only one of steps S70 and S72 may be performed.

[0098] If NG is determined in step S74, optical axis adjustment is performed next (steps S52 to S56). On the other hand, if OK is determined in step S74, countermeasures other than optical axis adjustment are required for the kerf inspection error and a detection position error of the laser scanning microscope LSM. Therefore, an error message is output, and the processing is stopped without executing optical axis adjustment (step S76).

[0099] Since the position of the optical axis of the laser light L1 is detected at two or more detection positions, the optical axis of the laser light L1 can be limited to a single axis. This makes it possible, for example, to allow the laser light L1 to enter the optical element perpendicularly or to limit the reflection angle on the mirror to 45°. Furthermore, the present embodiment can limit, for example, fluctuations in the positional relationship between the optical element and the laser beam to 50 μm or less, so that the quality of laser processing can be maintained automatically and without the intervention of an engineer.

[0100] In addition, the directional stability of the laser head LH may deteriorate due to temperature changes in the external environment, resulting in a deviation in the irradiation position of the laser light L1. Even if the irradiation position of the laser light L1 incident on the beam expander BE has changed, the optical axis adjustment according to the present embodiment can correct the deviation in the irradiation position of the laser light L1. [Second embodiment]

[0101] Although the optical axis adjustment is performed in accordance with the position of the laser light L1 detected by the position-sensitive detectors PSD1 and PSD2 in the above embodiment, the deviation of the beam expander BE can also affect the beam profile at the processing point and impair the quality of laser processing. Therefore, in addition to or instead of the above embodiment, the optical axis adjustment can also be performed for the beam expander BE.

[0102] In a second embodiment, the beam expander BE is designed such that it can be retracted from the optical path of the laser light L1 (be present therein and withdrawn therefrom). The process of retracting the beam expander BE can be performed manually or automatically by an actuator controllable by the control unit 50.

[0103] The Fig. 11 and Fig. 12 are flowcharts showing an optical axis adjustment method according to the second embodiment. Note that in the following description, components similar to those of the above embodiment are denoted by identical reference numerals to avoid description.

[0104] First, the optical axis adjustment (pre-adjustment) is carried out before starting laser processing using Fig. 11 described.

[0108] When performing the pre-adjustment, the position of the laser light L1 is first detected with the position-sensitive detectors PSD1 and PSD2, while the beam expander BE is withdrawn from the optical path of the laser light L1 (step S100).

[0105] Next, the beam expander BE is inserted into the optical path of the laser light L1, and the magnification of the beam expander BE is set to 1x (one). Then, the position of the laser light L1 in the state where the beam expander BE is inserted into the optical path of the laser light L1 is compared with the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1 to perform optical axis adjustment (step S102).

[0106] At this time, in step S102, it is not necessary to completely match the position of the laser light L1 in the state where the beam expander BE is located in the optical path of the laser light L1 with the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1. For example, a difference between the position of the laser light L1 in the state where the beam expander BE is located in the optical path of the laser light L1 and the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1 may be equal to or smaller than a prescribed threshold.

[0107] The adjustment of the optical axis after the start (during execution) of the laser processing is described below with reference to Fig. 12 described.

[0108] First, the magnification of the beam expander BE is set to the magnification required for laser processing (step S110), and the position of the laser light L1 is detected and recorded using the position-sensitive detectors PSD1 and PSD2 (step S112).

[0109] During laser processing, the position of the laser light L1 is then detected using the position-sensitive detectors PSD1 and PSD2 (step S114). In step S114, as in Fig. As shown in Figure 4, OK is determined when the difference r between the irradiation position (actual value) of the laser light L1 and the reference value is equal to or less than the threshold value rth, and NG is determined when the difference r exceeds the threshold value rth. Then, if OK is determined in step S114, the machining process continues without executing the optical axis adjustment. On the other hand, if NG is determined in step S114, the optical axis adjustment is executed (step S116).

[0110] In step S116, as in step S102, the position of the laser light L1 in the state where the magnification of the beam expander BE is set to 1x (one) and the beam expander BE is located in the optical path of the laser light L1 is compared with the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1, thereby performing optical axis adjustment.

[0111] After completing the optical axis adjustment (step S116), the magnification of the beam expander BE is adjusted to the magnification required for laser processing (step S110), the position of the laser light L1 is detected and recorded using the position-sensitive detectors PSD1 and PSD2, and then laser processing resumes. Subsequently, laser processing is terminated (step S118), and the device is stopped.

[0112] In the present embodiment, after step S118, an error in the kerf inspection and a check of the detection position of the laser scanning microscope LSM can be carried out in the same manner as in the Fig. 10 shown example.

[0113] The Fig. 13A and Fig. 13B are diagrams showing the detection results of the laser light L1 before and after adjusting the position of the beam expander. Fig. 13A and Fig. 13B, the brighter the color, the higher the intensity of the laser light L1.

[0114] If the beam expander BE deviates by 200 µm, the beam profile of the laser light L1 is distorted (offset), as shown in Fig. 13B. On the other hand, when the position of the beam expander BE is moved in the adjustment direction and the laser light L1 is adjusted to the reference position, the beam profile assumes an approximately circular shape in which the laser light L1 is evenly distributed in the roll and pitch directions, as shown in Fig. 13A is shown.

[0115] The present embodiment makes it possible to maintain the quality of the beam profile of the laser light L1, so that the quality of laser processing can be maintained automatically and without the intervention of an engineer. [Modifications]

[0116] Although in the present embodiment, the magnification of the beam expander BE during the adjustment of the optical axis (steps S102 and S116) is set to 1x (one), the present invention is not limited thereto. At the time of adjusting the optical axis, the magnification of the beam expander BE may be set to a magnification other than 1x. Furthermore, both the optical axis adjustment by setting the magnification of the beam expander BE to 1x and the optical axis adjustment by setting the magnification of the beam expander BE to a magnification other than 1x may be performed.

[0117] When the magnification of the beam expander BE is set to 1x, the beam expander BE can be considered the optical equivalent of a transparent plate. In this case, the difference (deviation amount) between the position of the laser light L1 when the beam expander BE is positioned in the optical path of the laser light L1 and the position of the laser light L1 when the beam expander BE is retracted from the optical path of the laser light L1 can be evaluated as the result of the inclination (tilt) of the beam expander BE with respect to the optical axis of the laser light L1.

[0118] In the second embodiment, the position of the laser light L1 in the state where the beam expander BE is located in the optical path of the laser light L1 is adjusted to the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1, so as to make the deviation amount approximately zero (see steps S102 and S116). This makes it possible to adjust the inclination of the beam expander BE with respect to the optical axis of the laser light L1 and to arrange the optical axis of the beam expander BE parallel to the optical axis of the laser light L1.

[0119] When the magnification of the beam expander BE is set to a magnification other than 1x, a beam diameter of the laser light L1 is expanded according to the magnification setting. In this case, a difference (deviation amount) between the position of the laser light L1 in the state where the beam expander BE is located in the optical path of the laser light L1 and the position of the laser light L1 in the state where the beam expander BE is retracted from the optical path of the laser light L1 can be evaluated as a result of parallel deviation. Parallel deviation is the deviation of the optical axis of the beam expander BE from the optical axis of the laser light L1 and appears as a deviation of the incident position in a plane perpendicular to the optical axis of the laser light L1.

[0120] In this case, too, the position of the laser light L1 in the state in which the beam expander BE has been moved into the optical path of the laser light L1 is compared with the position of the laser light L1 in the state in which the beam expander BE is retracted from the optical path of the laser light L1 to adjust the amount of deviation approximately to zero (see steps S102 and S116). In this way, the parallel deviation of the beam expander BE to the optical axis of the laser light L1 can be adjusted.

[0121] As described above, the inclination and parallel deviation of the beam expander BE can be adjusted by changing the magnification in the state where the beam expander BE is in the beam path.

[0122] It should be noted that when the magnification of the beam expander BE is set to 1x, the optical axis can be adjusted by rotating the beam expander BE with respect to the optical axis of the laser light L1. On the other hand, when the magnification of the beam expander BE is set to a magnification other than 1x, an adjustment axis of the beam expander BE is limited to the parallel direction. Specifically, the beam expander BE can be moved while maintaining the inclination of the beam expander BE with respect to the optical axis of the laser light L1 to adjust the optical axis. In other words, it is possible to limit the axis to be adjusted for optical axis adjustment depending on whether the magnification of the beam expander BE is 1x or other than 1x. [Third Embodiment]

[0123] Each of the above explanations explains the cases in which the beam expander BE is normal. However, there may also be cases in which the beam expander BE is abnormal. An abnormal beam expander BE occurs, for example, when the lenses contained in the beam expander BE are not arranged coaxially with each other or when the inclinations of the lenses are different.

[0124] Consider a case where the magnification of the beam expander BE is successively changed to 1x, 1.2x, 1.4x, 1.6x, ..., 4x, etc., and the coordinates of the irradiation position of the laser light L1 are recorded for each magnification. When the beam expander BE is normal and the optical axis is properly adjusted, the coordinates of the irradiation position of the laser light L1 do not change. In contrast, when the beam expander BE is normal but there is a tilt or parallel deviation (deviation of the incident position), or both a tilt and parallel deviation (as in a case where the optical axis adjustment is not performed), the coordinates of the irradiation position of the laser light L1 change linearly.

[0125] In contrast, when the beam expander BE is deviated, the coordinates of the irradiation position of the laser light L1 show a change (e.g., a nonlinear movement or the like) that is different from the movement or change in the case of a normal beam expander BE.

[0126] In the present embodiment, the quality of the beam expander BE is determined based on the above characteristics. Note that the quality determination of the beam expander BE can be performed regardless of whether the optical axis adjustment described above is performed.

[0127] Fig. 14 is a flowchart showing a first example of the quality determination method for the beam expander. Fig. 14 shows the quality determination procedure in a case where the adjustment of the optical axis of the beam expander BE was performed.

[0128] When the laser processing device 10 is activated and initialized, a laser idle state is first established (step S200). Then, the magnification of the beam expander BE is changed, and the irradiation position of the laser light L1 is detected and recorded at each magnification (step S202).

[0129] Next, it is determined whether the amount of movement of the irradiation position of the laser light L1 due to the change in the magnification of the beam expander BE is equal to or less than the reference value (step S204). For example, the reference value in step S204 is a positive value close to zero.

[0130] When the movement amount of the irradiation position of the laser light L1 due to the change in the magnification of the beam expander BE is equal to or smaller than the reference value (Yes in step S204), the quality of the beam expander BE is determined to be good (step S206).

[0131] When the movement amount of the irradiation position of the laser light L1 due to the change in the magnification of the beam expander BE exceeds the reference value (No in step S204), the quality of the beam expander BE is determined to be defective (step S208).

[0132] Fig. Figure 15 is a flowchart showing a second example of the quality determination procedure for the beam expander. Fig. 15 shows the quality determination procedure when the adjustment of the optical axis of the beam expander BE is not performed.

[0133] When the laser processing device 10 is activated and initialized, the laser idle state is first activated (step S220). Then, the magnification of the beam expander BE is changed, and the irradiation position of the laser light L1 is detected and recorded at each magnification (step S222).

[0134] Next, it is determined whether the irradiation position of the laser light L1 shifts linearly due to the change in the magnification of the beam expander BE (step S224). In step S224, it is possible to evaluate whether the irradiation position of the laser light L1 shifts linearly, for example, depending on whether a correlation coefficient is close to 1 when plotting the irradiation position of the laser light L1 at each magnification.

[0135] If it is determined that the irradiation position of the laser light L1 shifts linearly due to the change in the magnification of the beam expander BE (Yes in step S224), the quality of the beam expander BE is determined to be good (step S226).

[0136] If it is determined that the irradiation position of the laser light L1 does not shift linearly due to the change in the magnification of the beam expander BE (No in step S224), the quality of the beam expander BE is determined to be defective (step S226).

[0137] In the present embodiment, the quality determination for the beam expander BE can be performed, for example, before and after the optical axis adjustment. For example, the quality determination for the beam expander BE can be performed before the optical axis adjustment, so that the beam expander BE can be adjusted or replaced. This can improve the accuracy of the optical axis adjustment with the beam expander BE.

[0138] It should be noted that there are no specific time limits for performing the quality assessment of the beam expander BE. The quality assessment of the beam expander BE can also be performed at other times, such as during system commissioning and during laser processing. [Fourth Embodiment]

[0139] Fig. 16 is a block diagram showing an example of an illumination optical system in a fourth embodiment of the present invention. Fig. 16 shows an example in which an optical element for laser light shaping SE is arranged between the beam expander BE and the half mirror M5.

[0140] The laser light shaping optical element SE is an optical element for adjusting the state of the laser light L1 from the beam expander BE. Specifically, the laser light shaping optical element SE shapes the laser light L1 from the beam expander BE in accordance with the type of laser processing in the laser processing device 10. The type of laser processing here includes, for example, grooving with laser ablation, scribing, cutting, or drilling, or the formation of laser-modified regions that serve as starting points for cutting (breaking) the workpiece W.

[0141] The optical element for laser light shaping SE includes, for example, a refractive optical element (ROE), a cylindrical lens, or a mask. The ROE is a refracting optical element that shapes the beam shape of the laser light L1 into a desired shape (e.g., round shapes, ring shapes, line shapes, rectangular shapes, polygonal shapes, etc.). The cylindrical lens is a lens with a cylindrical portion. The cylindrical lens is an optical element for shaping the laser light L1 into a line beam shape or for expanding or contracting the laser light L1 only in one direction on a plane perpendicular to the optical axis of the laser light L1. The mask is an optical element that blocks part of the laser light L1 to shape the beam shape of the laser light L1.

[0142] Since the optical axis adjustment method according to each of the embodiments is applied in the present embodiment, it is possible to improve the accuracy of the irradiation position when the laser light shaping optical element SE is irradiated with the laser light L1 from the beam expander BE. This makes it possible to stabilize a beam shaping result of the laser light L1 emitted onto the laser light shaping optical element SE.

[0143] Although in the Fig. While the laser light shaping optical element SE is arranged between the beam expander BE and the half mirror M5 in the example shown in Figure 16, the present invention is not limited to this example. For example, the laser light shaping optical element SE may be arranged between the half mirror M5 and the mirror M6 or at other locations (positions downstream of the beam expander BE). List of reference symbols

[0144] 10...Laser processing device, 12...Table, 20...Laser irradiation device, 21...Laser light source, 22...Illumination optics, 23...Dichroic mirror, 24...Condenser lens, 25...Actuator, 30...AF device, 50...Control unit, 52...Adjustment mechanism, H1, H3...Holder, M1 to M3, M6 to M8...Mirrors, M4 to M5, M9...Half mirror, PSD1 to PSD2...Position-sensitive detector, LH...Laser head, ATN...Attenuator, BE...Beam expander, LZ1, LZ2...Relay lens, LSM...Laser scanning microscope, SE...Optical element for laser beam shaping QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2020-189323

[0005] JP 2017-022351

[0005]

Claims

[1] A method for adjusting an optical axis of laser light, comprising: a step of detecting a position of laser light emitted from a laser light source toward a workpiece using two paired position-sensitive detectors arranged at positions respectively after the laser light has passed through two paired half mirrors, the two half mirrors being respectively attached to an upstream side and a downstream side of a beam expander; and a step of adjusting, based on the position of the laser light, at least a position and an angle of two movable mirrors provided as a pair and arranged closer to the laser light source than the two half mirrors in an optical path of the laser light to adjust an optical axis of the laser light. [2] The method for adjusting an optical axis of laser light according to claim 1, wherein the two position-sensitive detectors are provided at a position on the workpiece other than the processing point to be irradiated with the laser light. [3] The method for adjusting an optical axis of laser light according to claim 1 or 2, wherein when a difference between the position of the laser light detected by the two position-sensitive detectors and a preset reference value is equal to or larger than a threshold value, an adjustment of the optical axis of the laser light is performed. [4] The method for adjusting an optical axis of laser light according to claim 3, wherein adjusting the position and / or angle of one of the two movable mirrors and setting the position of the laser light detected by one of the two position-sensitive detectors as a reference value are repeated for each of the movable mirrors to adjust the position of the laser light detected by each of the position-sensitive detectors to the respective reference position. [5] A device for adjusting an optical axis of laser light, comprising: two pairs of position-sensitive detectors arranged at positions after the laser light has passed through two pairs of half-mirrors, the two half-mirrors being attached to an upstream side and a downstream side of a beam expander, respectively; and an adjustment mechanism configured to adjust, based on a position of the laser light detected by each of the position-sensitive detectors, at least a position and an angle of two movable mirrors provided as a pair, which are arranged closer to a laser light source in an optical path of the laser light than the two half mirrors, to adjust an optical axis of the laser light. [6] A method for adjusting an optical axis of laser light, comprising: a step of detecting a position of laser light output from a laser light source toward a workpiece using position-sensitive detectors arranged respectively on an upstream side and a downstream side of a beam expander; and a step of moving the beam expander to adjust an optical axis of the laser light based on the position of the laser light detected by the position-sensitive detectors in a state where the beam expander is arranged in an optical path of the laser light and the position of the laser light detected by the position-sensitive detectors in a state where the beam expander is retracted from the optical path of the laser light. [7] The method for adjusting an optical axis of laser light according to claim 6, wherein, in the optical axis adjustment, the position of the laser light in a state where the magnification of the beam expander is set to 1 time is adjusted according to the position of the laser light in the state where the beam expander is retracted from the optical path of the laser light. [8] The method for adjusting an optical axis of laser light according to claim 6 or 7, wherein, in adjusting the optical axis, the position of the laser light in a state where the magnification of the beam expander is set to a value other than 1x is adjusted according to the position of the laser light in the state where the beam expander is retracted from the optical path of the laser light. [9] The method for adjusting an optical axis of the laser light according to any one of claims 6 to 8, comprising a step of performing a quality determination for the beam expander based on the change in the position of the laser light detected by the position sensitive detectors when the magnification of the beam expander is changed. [10] The method for adjusting an optical axis of laser light according to claim 9, wherein in the step of performing a quality determination, the quality of the beam expander is determined to be good when a movement amount of the position of the laser light detected by the position sensitive detectors is equal to or smaller than a reference value, or the position of the laser light changes linearly according to the change in the magnification of the beam expander. [11] A device for adjusting an optical axis of laser light, comprising: a beam expander retractably disposed in an optical path of laser light output from a laser light source toward a workpiece; position-sensitive detectors arranged on an upstream and a downstream side of the beam expander; and an adjustment mechanism configured to move the beam expander to adjust an optical axis of the laser light based on a position of the laser light detected by the position-sensitive detectors in a state where the beam expander is arranged in the optical path of the laser light and a position of the laser light detected by the position-sensitive detectors in a state where the beam expander is retracted from the optical path of the laser light.

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