Laser processing device

Abstract

The present application provides a laser processing device that can accurately confirm the state of a processing groove formed on the front surface of a wafer. The laser processing device includes a main photographing unit and an auxiliary photographing unit that photograph a region to be subjected to laser processing. The auxiliary photographing unit includes an objective lens, a camera that generates an image via the objective lens, a half mirror disposed between the camera and the objective lens, a light source that illuminates a wafer held by a chuck table via the half mirror and the objective lens, a first polarizing plate disposed between the camera and the half mirror, and a second polarizing plate disposed between the light source and the half mirror. The second polarizing plate is disposed in such a manner that the polarization plane of light emitted from the light source and reflected by the half mirror through the second polarizing plate becomes a state in which it is rotated by a desired angle with respect to the polarization axis of the first polarizing plate.

Description

Technical Field

[0001] This invention relates to a laser processing apparatus for performing laser processing by irradiating a wafer held in a chuck stage with laser light. Background Technology

[0002] A wafer with ICs, LSIs, and other devices formed on its front side by multiple intersecting pre-defined dividing lines is divided into individual device chips by a cutting device and a laser processing device. The resulting device chips are used in electronic devices such as mobile phones and personal computers.

[0003] A laser processing apparatus includes at least: a chuck stage for holding a wafer; a laser irradiation unit for irradiating the wafer held by the chuck stage with laser light to perform laser processing; a feed mechanism for feeding the chuck stage and the laser irradiation unit relative to each other; an imaging unit for imaging the area to be laser processed; and a display unit. This laser processing apparatus is capable of performing laser processing on wafers with high precision (see, for example, Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2004-188475

[0005] When forming a groove on the front side of a wafer using a laser processing apparatus through ablation, the laser processing conditions need to be appropriately set according to the wafer's material and thickness. To confirm whether these settings are appropriate, it is sometimes necessary to check the actual state of the groove formed on the front side of the wafer. When using the conventional imaging unit, which is already present in the laser processing apparatus and is used in the alignment process, to photograph the state of the groove, debris generated by the ablation process adheres to both sides of the groove. Therefore, it is difficult to distinguish between the groove and the debris, and thus it is impossible to accurately grasp the formation of the groove. Summary of the Invention

[0006] Therefore, the object of the present invention is to provide a laser processing apparatus that can accurately confirm the state of the processing grooves formed on the front side of a wafer.

[0007] According to the present invention, a laser processing apparatus is provided, comprising: a chuck stage for holding a wafer; a laser irradiation unit for irradiating the wafer held by the chuck stage with laser light to perform laser processing; a feed mechanism for feeding the chuck stage and the laser irradiation unit relative to each other; a main imaging unit for imaging an area to be laser processed; an auxiliary imaging unit; and a display unit, the auxiliary imaging unit comprising: an objective lens; a camera for generating an image via the objective lens; a semi-reflective mirror disposed between the camera and the objective lens; a light source for illuminating the wafer held by the chuck stage via the semi-reflective mirror and the objective lens; a first polarizing plate disposed between the camera and the semi-reflective mirror; and a second polarizing plate disposed between the light source and the semi-reflective mirror, the second polarizing plate being configured such that the polarization plane of light irradiated from the light source and reflected by the semi-reflective mirror after passing through the second polarizing plate is rotated by a desired angle relative to the polarization axis of the first polarizing plate.

[0008] Preferably, the auxiliary imaging unit is configured to image the laser-processed area of ​​the wafer held by the chuck stage, thereby capturing the processing grooves and debris formed by the laser processing. Preferably, the first polarizer and the second polarizer constituting the auxiliary imaging unit can be selectively positioned in an active position and an inactive position. When the first polarizer and the second polarizer are positioned in the inactive position, the main imaging unit is formed. Preferably, the required angle is 90 degrees.

[0009] According to the laser processing apparatus of the present invention, the contrast between the processing groove and the debris formed by laser processing is clear, and the formation of the processing groove can be well confirmed. Attached Figure Description

[0010] Figure 1 This is a three-dimensional view of the laser processing equipment.

[0011] Figure 2 It shows the installation at Figure 1 The image shows a three-dimensional view of the laser processing device's imaging unit functioning as the main imaging unit.

[0012] Figure 3 This is a perspective view illustrating an implementation method of the laser processing procedure.

[0013] Figure 4 It is shown Figure 2 The image shown is a 3D view of the shooting unit in a state where it functions as an auxiliary shooting unit.

[0014] Label Explanation

[0015] 2: Laser processing device; 3: Base; 6: Laser irradiation unit; 61: Condenser; 7: Imaging unit; 71: Objective lens; 72: Camera; 73: Semi-reflective mirror; 74: Light source; 75: First polarizing plate; 76: Second polarizing plate; 77: First polarizing plate holding plate; 77a: Opening; 78: Second polarizing plate holding plate; 78a: Opening; 10: Wafer; 12: Device; 14: Pre-defined dividing line; 20: Holding unit; 21: Movable plate in the X-axis direction; 22: Movable plate in the Y-axis direction; 25: Chuck stage; 30: Feed mechanism; 31: X-axis moving mechanism; 32: Y-axis moving mechanism; 37: Frame; 37a: Vertical wall; 37b: Horizontal wall; 100: Control unit; 110: Processing tank; 120: Debris. Detailed Implementation

[0016] Hereinafter, the laser processing apparatus according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0017] exist Figure 1 The figure shows an overall perspective view of the laser processing apparatus 2 of this embodiment. As shown, the workpiece processed by the laser processing apparatus 2 of this embodiment is a disc-shaped wafer 10, which is held in an annular frame F by means of an adhesive tape T.

[0018] The laser processing apparatus 2 includes: a chuck stage 25 for holding a wafer 10; a laser irradiation unit 6 for irradiating the wafer 10 held by the chuck stage 25 with laser light to perform laser processing; a feed mechanism 30 for feeding the chuck stage 25 and the laser light irradiated from the laser irradiation unit 6 relative to each other; an imaging unit 7 that serves as both a main imaging unit and an auxiliary imaging unit, wherein the main imaging unit images the area to be laser processed and the auxiliary imaging unit images the processing grooves and debris formed by the laser processing; and a display unit 8.

[0019] The holding unit 20, including the chuck stage 25, comprises on the base 3: a rectangular X-axis movable plate 21, which is movably mounted in the X-axis direction; a rectangular Y-axis movable plate 22, which is movably mounted in the Y-axis direction along guide rails 21a, 21a on the X-axis movable plate 21; a cylindrical support column 23, which is fixed to the upper surface of the Y-axis movable plate 22; and a rectangular cover plate 26, which is fixed to the upper end of the support column 23. The chuck stage 25 is a circular component extending upward through an elongated hole formed in the cover plate 26, configured to be rotatable by a rotary drive unit (not shown). The chuck stage 25 is formed of a porous material with ventilation properties and has a holding surface 25a defined by the X-axis and Y-axis directions. The holding surface 25a is connected to an attraction unit (not shown) via a flow path through the support column 23. Furthermore, the X-axis direction is... Figure 1The direction indicated by the middle arrow X is perpendicular to the direction indicated by the arrow Y. The plane defined by the X-axis and Y-axis is essentially horizontal.

[0020] The feed mechanism 30 includes: an X-axis moving mechanism 31, which moves the chuck table 25 of the holding unit 20 and the laser beam irradiated from the laser irradiation unit 6 relative to each other in the X-axis direction for machining feed; and a Y-axis moving mechanism 32, which moves the chuck table 25 and the laser beam irradiated from the laser irradiation unit 6 relative to each other in the Y-axis direction. The X-axis moving mechanism 31 includes: a ball screw 34, which extends along the X-axis direction on the base 3; and a motor 33, which is connected to one end of the ball screw 34. The nut portion (not shown) of the ball screw 34 is formed on the lower surface of the movable plate 21 in the X-axis direction. Furthermore, the X-axis moving mechanism 31 converts the rotational motion of the motor 33 into linear motion via the ball screw 34 and transmits it to the movable plate 21 in the X-axis direction, causing the movable plate 21 in the X-axis direction to move forward and backward along the guide rails 3a, 3a on the base 3 in the X-axis direction. The Y-axis moving mechanism 32 includes a ball screw 36 extending along the Y-axis direction on a movable plate 21 in the X-axis direction; and a motor 35 connected to one end of the ball screw 36. A nut portion (not shown) of the ball screw 36 is formed on the lower surface of the movable plate 22 in the Y-axis direction. The Y-axis moving mechanism 32 converts the rotational motion of the motor 35 into linear motion via the ball screw 36 and transmits it to the movable plate 22 in the Y-axis direction, causing the movable plate 22 to move forward and backward along the guide rails 21a, 21a on the movable plate 21 in the X-axis direction.

[0021] A frame 37 is erected vertically inside the holding unit 20. This frame 37 has a vertical wall 37a extending upwards (in the Z-axis direction) from the upper surface of the base 3 and a horizontal wall 37b extending horizontally. An optical system comprising a laser irradiation unit 6 and an imaging unit 7 is housed within the horizontal wall 37b. A condenser 61 constituting the laser irradiation unit 6 is disposed on the lower front surface of the horizontal wall 37b, and an objective lens 71 of the imaging unit 7 is disposed at a distance from the condenser 61 in the X-axis direction. The laser irradiation unit 6 is a unit that irradiates laser light of a wavelength that is absorbed by the wafer 10, and is configured for laser processing conditions that perform ablation processing on the front side of the wafer 10. The illustrated objective lens 71 shows the case where the objective lens is housed within a cylindrical housing. A display unit 8 is disposed above the horizontal wall 37b. The laser irradiation unit 6, the imaging unit 7, the display unit 8, the moving unit 30, etc., described above are electrically connected to the control unit described later, and are controlled according to the instruction signal indicated by the control unit to perform laser processing on the wafer 10.

[0022] Reference Figure 2The imaging unit 7 of this embodiment will be described. Figure 2 The optical system of the imaging unit 7 housed in the horizontal wall portion 37b of the frame 37 (omitted for ease of explanation) is shown in the diagram. As described above, the imaging unit 7 of this embodiment also serves as the main imaging unit 7A for imaging the area to be laser-processed, as described later, and as the auxiliary imaging unit 7B for imaging the grooves and debris formed by laser processing (see reference). Figure 4 ), Figure 2 The image shows the state in which the imaging unit 7A functions as the main imaging unit 7A to capture the area to be laser-processed.

[0023] like Figure 2 As shown, the imaging unit 7 includes: an objective lens 71; a camera 72 that generates an image via the objective lens 71; a semi-reflective mirror 73 disposed between the camera 72 and the objective lens 71; a light source 74 that illuminates the wafer 10 held by the chuck stage 25 via the semi-reflective mirror 73 and the objective lens 71; a first polarizing plate 75 disposed between the camera 72 and the semi-reflective mirror 73; and a second polarizing plate 76 disposed between the light source 74 and the semi-reflective mirror 73. The light source 74 is, for example, a light source that illuminates visible light L1. The first polarizing plate 75 is a polarizing plate whose polarization axis is set in a predetermined direction (the Y-axis direction in this embodiment), and is a polarizing plate that allows only light vibrating in the Y-axis direction to pass through when light passes through the first polarizing plate 75. In contrast, in Figure 2 In the illustrated embodiment, the polarization axis of the second polarizing plate 76 is set in the up-down direction as indicated by arrow Z. Therefore, the polarization axis of the light irradiated from the light source 74, passing through the second polarizing plate 76, and reflected by the semi-reflective mirror 73 is configured to be rotated 90 degrees relative to the polarization axis of the first polarizing plate 75, i.e., configured in the X-axis direction perpendicular to the Y-axis direction. The camera 72 is connected to the control unit 100, and the image transmitted from the camera 72 to the control unit 100 is displayed on the display unit 8. Furthermore, in the above embodiment, the polarization axis of the visible light L1 irradiated from the light source 74, after passing through the second polarizing plate 76 and being reflected by the semi-reflective mirror 73, is configured to be rotated 90 degrees relative to the polarization axis of the first polarizing plate 75. However, the present invention is not limited to this; the polarization axis of the visible light L1 after passing through the second polarizing plate 76 and being reflected by the semi-reflective mirror 73 can be appropriately rotated relative to the polarization axis of the first polarizing plate 75 according to the state of the front side of the wafer 10. That is, the polarization axis of the second polarizing plate 76 only needs to be rotated by the required angle relative to the polarization axis of the first polarizing plate 75, and is not limited to being set along the X-axis or Y-axis.

[0024] Furthermore, in this embodiment, the first polarizing plate 75 of the imaging unit 7 is held on the first polarizing plate holding plate 77, and the second polarizing plate 76 is held on the second polarizing plate holding plate 78. The first polarizing plate holding plate 77 and the second polarizing plate holding plate 78 are held by a holding mechanism (not shown) and are configured to be movable in the horizontal direction. In addition, an opening 77a is formed on the first polarizing plate holding plate 77. By moving the first polarizing plate holding plate 77 in the direction indicated by arrow R1, when the camera 72 is used to photograph the wafer 10 held by the chuck stage 25, it is possible to selectively move from the active position where the first polarizing plate 75 is active to the inactive position where the first polarizing plate 75 is inactive. Similarly, an opening 78a is also formed on the second polarizing plate holding plate 78. By moving the second polarizing plate holding plate 78 in the direction indicated by arrow R2, when light L1 is irradiated from the light source 74, it can selectively move from the working position where light L1 passes through the second polarizing plate 76 to the non-working position where the second polarizing plate 76 does not function. Figure 2 The imaging unit 7 shown moves both the first polarizing plate holding plate 77 and the second polarizing plate holding plate 78 to the aforementioned non-functional position. Thus, the imaging unit 7 functions as the main imaging unit 7A, which captures images of the area to be laser-processed via the camera 72.

[0025] The laser processing apparatus 2 of this embodiment has a structure roughly as described above, and the functions and effects of this embodiment will be explained below.

[0026] When performing laser processing using the laser processing apparatus 2 of this embodiment, firstly as follows: Figure 1 As shown, the wafer 10 is transported to the laser processing apparatus 2 and held in the chuck stage 25 of the holding unit 20. As shown, the wafer 10 is divided by multiple intersecting predetermined dividing lines 14, and multiple devices 12 are formed on its front side. Next, the feed mechanism 30 is activated to position the wafer 10 held by the chuck stage 25 directly below the objective lens 71 of the imaging unit 7. At this time, the imaging unit 7, according to… Figure 2 As explained, the first polarizer holding plate 77 and the second polarizer holding plate 78 are positioned in a non-functional position, thus enabling the main imaging unit 7A to function as the main imaging unit for capturing images of the area to be laser-processed. Next, as... Figure 2As shown, visible light L1 irradiated from the light source 74 passes through the opening 78a of the second polarizer holding plate 78 (which is in an inactive position) and is reflected on the reflecting surface 73b of the semi-reflecting mirror 73 as indicated by arrow R3, and is guided to the objective lens 71. The visible light L1 reflected on the reflecting surface 73b of the semi-reflecting mirror 73 is reflected on the wafer 10 held by the chuck stage 25, becoming reflected light L2, which is guided through the objective lens 71 to the semi-reflecting mirror 73, and passes through the reflecting surface 73b and upper surface 73a of the semi-reflecting mirror 73 (a portion of the reflected light L2 is reflected towards the light source 74). Furthermore, the reflected light L2 passes through the opening 77a of the first polarizer holding plate 77 and is guided to the camera 72 as indicated by arrow R4. Thus, the camera 72 generates an image, which is displayed on the display unit 8 via the control unit 100. Figure 2 As shown, the image generated by camera 72 includes a predetermined dividing line 14, which serves as the area to be laser-processed to form a machining groove. The position of this predetermined dividing line 14 is detected. Next, the chuck stage 25 is rotated by the aforementioned rotary drive unit, aligning the predetermined dividing line 14 with the X-axis direction. The position of the area to be processed is stored in the control unit 100, completing the alignment process. If the alignment process is performed, refer to... Figure 3 Perform the laser processing steps described below.

[0027] Based on the position information of the pre-defined dividing line 14 detected by the alignment process described above, the chuck stage 25 is moved to position the concentrator 61 of the laser beam irradiation unit 6 directly above the processing start position of the pre-defined dividing line 14 in the first direction. The focusing point of the laser beam LB is positioned on the pre-defined dividing line 14 of the wafer 10 for irradiation. The wafer 10 and the chuck stage 25 are fed together in the X-axis direction for processing, and ablation processing is performed along the pre-defined dividing line 14 in the first direction of the wafer 10 to form a processing groove 110. If a processing groove 110 is formed along the pre-defined dividing line 14, the wafer 10 is indexed and fed in the Y-axis direction according to the intervals of the pre-defined dividing lines 14, and the adjacent unprocessed pre-defined dividing line 14 in the first direction in the Y-axis direction is positioned directly below the concentrator 61. Similarly, the focusing point of the laser beam LB is positioned on the pre-defined dividing line 14 of the wafer 10 for irradiation, and the wafer 10 is fed in the X-axis direction for processing to form a processing groove 110. Similarly, the wafer 10 is fed along the X and Y axes to form processing grooves 110 along all the predetermined dividing lines 14 in the first direction. Next, the wafer 10 is rotated 90 degrees so that the unprocessed dividing lines 14 in the second direction, which are perpendicular to the dividing lines 14 in the first direction where the processing grooves 110 have already formed, are aligned with the X-axis. Furthermore, for the remaining dividing lines 14 in the second direction, the laser beam LB is positioned and irradiated in the same manner as described above, forming processing grooves 110 along all the predetermined dividing lines 14 formed on the front side of the wafer 10, thus completing the laser processing step.

[0028] If the laser processing step is completed as described above, a processing groove confirmation step, as described below, is performed to confirm the formation of the processing groove 110. During this processing groove confirmation step, the feed mechanism 30 is activated to move the chuck stage 25, positioning the wafer 10 directly below the objective lens 71 of the imaging unit 7. At this time, as... Figure 4 As shown, the imaging unit 7 moves the first polarizing plate holding plate 77 to the operating position in the direction indicated by arrow R5, and moves the second polarizing plate holding plate 78 to the operating position in the direction indicated by arrow R6. Thus, the imaging unit 7 is positioned to function as an auxiliary imaging unit 7B, which images the laser-processed area of ​​the wafer 10 held by the chuck stage 25, i.e., the area where the processing groove 110 is formed, thereby capturing images of the processing groove 110 formed by laser processing and the debris (described later) adhering to both sides of the processing groove 110.

[0029] If, as described above, the wafer 10 with the processing groove 110 is positioned directly below the objective lens 71 of the imaging unit 7, which serves as the auxiliary imaging unit 7B, visible light L1 is irradiated from the light source 74. This visible light L1, through the second polarizer 76, causes the component L3, which vibrates only in the vertical direction, to travel in the direction indicated by arrow R7. It is guided to the reflecting surface 73b of the semi-reflective mirror 73 and reflected, then irradiates the area of ​​the wafer 10 with the processing groove 110 via the objective lens 71. The light L3 irradiating the area of ​​the wafer 10 containing the processing groove 110 is reflected in that area to become reflected light L4, which travels in the direction indicated by arrow R8 via the objective lens 71 and passes through the semi-reflective mirror 73 (partially reflected by the reflecting surface 73b). The reflected light L4, which passes through the semi-reflective mirror 73, is guided to the first polarizing plate 75. Thus, only the light L5 that passes through the first polarizing plate 75 in the reflected light L4 travels in the direction indicated by arrow R9 and generates an image through the camera 72. The image is then displayed on the display unit 8 via the control unit 100.

[0030] Here, the transmission of light L5 described above will be explained in more detail. As mentioned above, light L1 irradiated from light source 74 passes through a second polarizing plate 76 whose polarization axis is set in the vertical direction (Z-axis direction). Consequently, the polarization plane of light L3 reflected by the semi-reflective mirror 73 becomes the X-axis direction, rotated 90 degrees relative to the polarization axis of the first polarizing plate 75. When light L3 is reflected on the wafer 10, if specular reflection occurs on the wafer 10, the polarization plane of the reflected light does not change, remaining in the X-axis direction and is reflected. Conversely, when light L3 is reflected on the wafer 10, if reflection occurs at a portion of the wafer 10 with fine uneven surfaces, diffuse reflection is caused by these uneven surfaces, resulting in reflected light containing polarization planes in various directions. Here, when a component of the reflected light L4, which has undergone specular reflection on the wafer 10 in this embodiment, is guided to the first polarizer 75, the polarization axis of the first polarizer 75 is oriented towards the Y-axis direction. Therefore, the component of the reflected light L4 with its polarization plane in the X-axis direction is blocked by the first polarizer 75 and cannot pass through. In contrast, when the reflected light L4 contains a component that has undergone diffuse reflection on the wafer 10, when the reflected light L4 is guided to the first polarizer 75, due to the presence of light components in the direction of the polarization axis (Y-axis direction) of the first polarizer 75 and the polarization plane close to the Y-axis direction, this reflected light passes through the first polarizer 75 and reaches the camera 72 to generate an image.

[0031] like Figure 4As shown, when light L3 illuminates the area where the machining groove 110 is appropriately formed, light L3 constitutes reflected light that mainly undergoes specular reflection and has little diffuse reflection in this area. In contrast, the debris formed on both sides of the machining groove 110 contains fine uneven surfaces, so light L3 illuminating this area constitutes reflected light that undergoes diffuse reflection and contains polarization planes in various directions. When the reflected light L4 generated by specular and diffuse reflection is guided to the first polarizing plate 75, the component of reflected light generated by specular reflection is blocked, forming transmitted light L5, in which only light with polarization planes in the Y-axis direction and near the Y-axis direction passes through the diffuse reflection generated at the debris. This transmitted light L5 is guided to the camera 72, generating an image and displaying it on the display unit 8 (machining groove confirmation process). As a result, as... Figure 4 As shown, the contrast between the machining groove 110 and the debris 120 is clear, allowing for a good assessment of the formation of the machining groove 110. Furthermore, for ease of explanation, the following is shown... Figure 4 The image on display unit 8 shows a black-and-white inverted image.

[0032] In this embodiment, the first polarizing plate 75 and the second polarizing plate 76 are held by the first polarizing plate holding plate 77 and the second polarizing plate holding plate 78, so that they can be selectively positioned at the active position and the inactive position. This configuration serves as a shooting unit 7 that also functions as the main shooting unit 7A and the auxiliary shooting unit 7B, thereby preventing the space for the shooting unit from being too large.

[0033] In the above embodiment, the imaging unit 7 is configured to serve as both the main imaging unit 7A and the auxiliary imaging unit 7B. However, the present invention is not limited to this. The main imaging unit 7A and the auxiliary imaging unit 7B may also be configured as independent units, and the above-mentioned alignment process and processing groove confirmation process may be performed by the separately configured main imaging unit 7A and auxiliary imaging unit 7B.

[0034] Furthermore, in the above embodiment, an example of laser processing is shown using a wafer 10 with multiple devices 12 formed on its front surface by being divided by multiple intersecting predetermined dividing lines 14. However, the present invention is not limited to this, and a so-called replica wafer without devices 12 can also be used. Additionally, in the above embodiment, an example is shown where the polarization axis of the second polarizer 76 is rotated 90 degrees relative to the polarization axis of the first polarizer 75. However, as long as the required angle is rotated, i.e., an angle greater than 0 degrees, the effect of blocking reflected light that has undergone specular reflection on the front surface of the wafer 10 can be obtained.

Claims

1. A laser processing apparatus, wherein, This laser processing device has the following features: A chuck stage that holds the wafer; A laser irradiation unit that performs laser processing by irradiating the wafer held on the chuck stage with laser light; The feeding mechanism feeds the chuck table and the laser irradiation unit relative to each other during processing. The main imaging unit captures images of the area to be laser-processed. Auxiliary shooting unit; and Display unit, This auxiliary imaging unit includes: Objective lens; A camera that generates an image through the objective lens; A semi-reflective mirror, which is disposed between the camera and the objective lens; A light source that illuminates the wafer held by the chuck stage via the semi-reflective mirror and the objective lens; A first polarizing plate, disposed between the camera and the semi-reflective mirror; and The second polarizing plate is disposed between the light source and the semi-reflective mirror. The second polarizing plate is configured such that the polarization plane of the light irradiated from the light source and reflected by the semi-reflective mirror after passing through the second polarizing plate is rotated by a required angle relative to the polarization axis of the first polarizing plate.

2. The laser processing apparatus according to claim 1, wherein, The auxiliary imaging unit is configured to image the laser-processed area of ​​the wafer held by the chuck stage, thereby capturing the processing grooves and debris formed by laser processing.

3. The laser processing apparatus according to claim 1, wherein, The first polarizing plate and the second polarizing plate constituting the auxiliary shooting unit can be selectively positioned in an active position and an inactive position. When the first polarizing plate and the second polarizing plate are positioned in the inactive position, the main shooting unit is formed.

4. The laser processing apparatus according to claim 1, wherein, The required angle is 90 degrees.

Images