JP2023135899A - Photodetection device, light irradiation device, and photodetection method - Google Patents

Abstract

To provide a technique that can reduce the occurrence of interference fringes due to reflection from a back surface of a cover glass when capturing an image of laser light with a camera.SOLUTION: A photodetection unit 60a is capable of detecting laser light. The photodetection unit 60a includes a diffuser plate 61 and a camera 63. The diffuser plate 61 diffuses a laser beam L1 while maintaining the shape of the intensity distribution of the incident laser beam L1. The camera 63 includes an image sensor 631 and a cover glass 633. The image sensor 631 images diffused laser light diffused by the diffuser plate 61. The cover glass 633 is located between the diffuser plate 61 and the image sensor 631.SELECTED DRAWING: Figure 4

Description

The subject matter disclosed herein relates to a photodetection device, a light irradiation device, and a photodetection method.

BACKGROUND ART Conventionally, a light irradiation device has been proposed that captures an image of laser light with a camera, measures the beam diameter and parallelism from the image of the laser light, and adjusts the laser light (for example, Patent Document 1).

JP 2021-089383 Publication

However, when capturing an image of laser light with a camera, the laser light reflected from the back surface of a cover glass for sealing an image sensor such as a CMOS or CCD may interfere with the original laser light, resulting in interference fringes. there were. When such interference fringes occur, it becomes difficult to accurately detect the center of the laser beam.

An object of the present invention is to provide a technique that can reduce the occurrence of interference fringes due to backside reflection on a cover glass when capturing an image of laser light with a camera.

In order to solve the above-mentioned problems, a first aspect is a photodetection device that detects laser light, which includes a diffusion section that diffuses the laser light while maintaining the shape of the intensity distribution of the incident laser light, and the diffusion section. and a camera having a cover glass located between the diffusion section and the image sensor.

A second aspect is the photodetection device of the first aspect, in which the image sensor is a two-dimensional image sensor.

A third aspect is the photodetection device of the second aspect, further comprising a center position calculation unit that calculates the center position of the laser beam based on an image acquired by the image sensor.

A fourth aspect is the photodetection device according to any one of the first to third aspects, wherein the camera further includes a housing provided with an opening through which the laser beam passes, and the image sensor Located within the housing, the cover glass closes the opening.

A fifth aspect is the photodetection device of the fourth aspect, in which the diffusion section is attached to the housing.

A sixth aspect is the photodetecting device according to any one of the first to fifth aspects, wherein the diffusion section includes frosted glass.

A seventh aspect is the photodetection device according to any one of the first to fifth aspects, in which the diffusion section includes a microlens array.

An eighth aspect is a light irradiation device, which includes: a holding part that holds a base material; a laser light source that outputs a laser beam; and a light irradiation device that transmits the laser light output from the laser light source to the base material that is held on the base material. an optical system that guides the laser beam to the material; and at least one photodetector that detects the laser beam, the at least one photodetector that detects the laser beam while maintaining the shape of the intensity distribution of the incident laser beam. The image sensor includes a diffusing section that diffuses the laser light, an image sensor that captures an image of the laser light diffused in the diffusing section, and a camera having a cover glass located between the diffusing section and the image sensor.

A ninth aspect is the light irradiation device according to the eighth aspect, wherein the optical system includes a first beam splitter that branches the laser light output from the laser light source, and a first beam splitter that branches the laser light output from the laser light source. a second beam splitter that splits the laser beam, and the at least one photodetector includes a first photodetector that detects the laser beam split by the first beam splitter, and a second beam splitter that splits the laser beam. and a second photodetector that detects the laser beam split by the splitter.

A tenth aspect is a light detection method for detecting laser light, comprising: a) diffusing the laser light while maintaining the shape of the intensity distribution of the laser light, and b) after the laser light is diffused in step a). , and a step of capturing an image of the laser beam transmitted through the cover glass using an image sensor.

According to the photodetecting devices of the first to seventh aspects, by diffusing the laser beam, it is possible to reduce the occurrence of interference fringes even if backside reflection occurs on the cover glass. Furthermore, since the shape of the intensity distribution before diffusion is maintained, the position of the laser beam can be accurately identified from the intensity distribution.

According to the photodetection device of the second aspect, the intensity distribution of laser light can be detected two-dimensionally.

According to the photodetector of the third aspect, the position of the optical axis of the laser beam can be detected.

According to the photodetecting device of the sixth aspect, light can be easily and uniformly diffused by the frosted glass.

According to the photodetection device of the seventh aspect, the spread angle and shape of the laser beam can be controlled by the microlens array.

According to the light irradiation device of the eighth aspect, by diffusing the laser light, the generation of interference fringes can be reduced even if back reflection occurs on the cover glass. Furthermore, since the shape of the intensity distribution before diffusion is maintained, the position of the laser beam can be accurately identified from the intensity distribution.

According to the light irradiation device of the ninth aspect, the parallelism of the laser beam can be measured based on the position of the laser beam detected by the first photodetector and the second photodetector.

According to the photodetection method of the tenth aspect, by diffusing the laser light, even if back reflection occurs on the cover glass, the generation of interference fringes can be reduced. Furthermore, since the shape of the intensity distribution before diffusion is maintained, the position of the laser beam can be accurately identified from the intensity distribution.

FIG. 1 is a perspective view schematically showing the configuration of a light irradiation device according to an embodiment. FIG. 2 is a cross-sectional view showing the internal configuration and peripheral configuration of a vacuum chamber included in the light irradiation device shown in FIG. 1. FIG. FIG. 3 is a perspective view schematically showing the configuration of the light irradiation section shown in FIGS. 1 and 2. FIG. FIG. 3 is a cross-sectional view schematically showing the configuration of a photodetector. It is a figure which shows the image of the laser beam acquired by the photodetection part, and the brightness distribution in the position shown by the broken line of the said image. It is a figure which shows the photodetection part based on a comparative example. It is a figure which shows the image of the laser beam acquired by the photodetection part based on a comparative example, and the brightness distribution in the position shown by the broken line of the said image.

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the components described in this embodiment are merely examples, and the scope of the present invention is not intended to be limited thereto. In the drawings, dimensions and numbers of parts may be exaggerated or simplified as necessary to facilitate understanding.

In FIG. 1 and the subsequent figures, arrows indicating mutually intersecting X, Y, and Z axes may be illustrated. The X, Y and Z axes are preferably orthogonal. Furthermore, the direction toward which the tip of each arrow points is defined as the + (plus) side, and the side opposite to the + side is defined as the - (minus) side.

In the following description, the direction along the Z-axis is defined as a vertical direction, and the directions along the X-axis and Y-axis are defined as horizontal directions parallel to the horizontal plane. Further, the +Z side will be described as the "upper side" and the -Z side will be described as the "lower side." However, these directions do not limit the positional relationship of the device configuration.

<1. Embodiment>
FIG. 1 is a perspective view schematically showing the configuration of a light irradiation device 1 according to an embodiment. In FIG. 1, illustration of a chamber frame that supports the vacuum chamber 12, wiring that is actually connected, etc. is omitted for convenience.

As shown in FIG. 1, the light irradiation device 1 includes a vacuum chamber 12, an external fixing section 14, a bellows 16A, a light irradiation section 18, a vacuum pump 21, and a control section 22.

The vacuum chamber 12 has a space in which the base material W is accommodated. The base material W is, for example, a semiconductor wafer, a glass substrate for a liquid crystal display device, a substrate for an FPD (Flat Panel Display) such as an organic EL (Electroluminescence) display device, a substrate for an optical disk, a substrate for a magnetic disk, a substrate for a magneto-optical disk, These are glass substrates for photomasks, ceramic substrates, field emission display (FED) substrates, or solar cell substrates. Note that the base material W is, for example, a substrate with a thin film formed on its upper surface.

Further, the side surface of the vacuum chamber 12 has an opening 12A through which the base material W passes when the base material W is carried in and carried out. The opening 12A is appropriately closed when the inside of the vacuum chamber 12 is brought into a vacuum state.

The external fixing part 14 is, for example, a stone surface plate. Bellows 16A connects vacuum chamber 12 and external fixing part 14. The bellows 16A is a stretchable member made of stainless steel, for example. The bellows 16A as a stretchable member may be made of metal or resin other than stainless steel. Further, the elastic member does not necessarily have a bellows shape.

The light irradiation unit 18 irradiates the inside of the vacuum chamber 12 with laser light. The light irradiation unit 18 irradiates the upper surface of the base material W housed in the vacuum chamber 12 with laser light. The light irradiation unit 18 performs ablation processing on the base material W by irradiating it with laser light, for example.

The light irradiation unit 18 irradiates light from outside the vacuum chamber 12 onto the upper surface of the base material W housed in the vacuum chamber 12 through an irradiation window (not shown) (for example, a transparent plate made of quartz or the like). . Further, the light scans the upper surface of the base material W by moving the base material W in the vacuum chamber 12 relative to the light irradiation section 18 or by controlling the optical system in the light irradiation section 18 . The light irradiation unit 18 is located on the upper surface of the pedestal 24 attached to the external fixing unit 14.

The vacuum pump 21 brings the inside of the vacuum chamber 12 into a vacuum state. In the present disclosure, "vacuum" is preferably a high vacuum (for example, 0.00001 Pa) in order to prevent property deterioration of the base material W, but also includes a degree of vacuum that does not reach the high vacuum. . For example, the degree of vacuum within the vacuum chamber 12 may be lower than the atmospheric pressure outside the vacuum chamber 12.

The control unit 22 includes a storage device, a processing circuit, an input device, and an output device. Storage devices include, for example, hard disk drives (HDD), random access memory (RAM), read-only memory (ROM), flash memory, volatile or nonvolatile semiconductor memory, magnetic disks, flexible disks, optical disks, compact disks, mini disks, etc. It consists of a memory (storage medium) including a disk or DVD. The processing circuit includes, for example, a central processing unit (CPU) that executes a program stored in a storage device. The input device is configured of a device capable of inputting information, such as a mouse, keyboard, touch panel, or various switches. The output device is constituted by a device capable of outputting information, such as a display, a liquid crystal display, or a lamp.

The control unit 22 controls each drive unit included in the light irradiation device 1. The control unit 22 performs, for example, drive control of the light irradiation unit 18, drive control of the vacuum pump 21, drive control of a linear motor mechanism 50, which will be described later. Further, the control unit 22 performs a process of calculating the center position of the laser beam based on the images acquired by the photodetectors 60a and 60b, as described later.

FIG. 2 is a cross-sectional view showing the internal configuration and peripheral configuration of the vacuum chamber 12 included in the light irradiation device 1 shown in FIG. As shown in FIG. 2, a stage 42, a slider 44, a base 46, a linear guide 48, a linear motor mechanism 50, and a lift pin mechanism 52 are arranged within the vacuum chamber 12.

The stage 42 has an upper surface on which the base material W is placed. The slider 44 is movable in the Y-axis direction and supports the stage 42 from below. The base 46 is attached to the external fixture 14 independently of the vacuum chamber 12. The linear guide 48 is attached to the base 46 and extends in the Y-axis direction. The linear motor mechanism 50 moves the slider 44 along the linear guide 48 in the Y-axis direction. The lift pin mechanism 52 has a lift pin 52A that passes through a through hole (not shown) formed in the stage 42 and supports the base material W. The lift pin mechanism 52 is attached to the base 46, for example.

The stage 42 holds the base material W substantially horizontally, with the processed surface of the base material W facing upward. By moving the slider 44 in the Y-axis direction by the linear motor mechanism 50 and moving the light from the light irradiation unit 18 in the X-axis direction, the entire processing area of the base material W is scanned with light in plan view. Ru.

The linear motor mechanism 50 is attached to the external fixing part 14 located on the +X side and the -X side of the vacuum chamber 12 through an opening 12B formed on the -X side of the vacuum chamber 12. Specifically, the linear motor mechanism 50 is attached to the end of the hollow columnar member 14A that passes through the bellows 16A that is welded to the opening 12B. Wiring and the like connected to the linear motor mechanism 50 are led out to the outside of the vacuum chamber 12 through the inside of the columnar member 14A. The columnar member 14A is located apart from the bellows 16A.

The base 46 is fixed to the external fixing part 14 located on the -Z side of the vacuum chamber 12 through an opening 12C formed in the bottom surface of the vacuum chamber 12. Specifically, the base 46 is attached to the end of the columnar member 14C that passes through the bellows 16B that is welded to the opening 12C. The columnar member 14C is attached to the external member 14B included in the external fixing section 14. The columnar member 14C is located apart from the bellows 16B connected to the bottom surface of the vacuum chamber 12.

In the example shown in FIG. 2, the external fixing part 14 is located at each position on the +X side, -X side, and -Z side of the vacuum chamber 12, but the external fixing part 14 is continuously located at these positions. It is not essential that they be located at the same location, and they may be distributed at these locations. Further, the external fixing part 14 may be arranged at some of the positions on the +X side, -X side, and -Z side of the vacuum chamber 12. Further, the vacuum chamber 12 is supported and fixed from vertically downward by a chamber frame (not shown) separately from the bellows 16B, but the chamber frame may be arranged independently of the external fixing part 14. good.

FIG. 3 is a perspective view schematically showing the configuration of the light irradiation section 18 shown in FIGS. 1 and 2. As shown in FIG. The light irradiation section 18 includes a laser light source 31, an optical system 35, and two light detection sections 60a and 60b (photodetection devices).

Laser light source 31 outputs laser light. The laser light output by the laser light source 31 may be continuous light or pulsed light. The optical system 35 guides the light output from the laser light source to the base material W held on the stage 42. The optical system 35 includes two beam splitters 350a and 350b, a wedge plate 351, an acousto-optic element 353, a beam expander 355, a galvano scanner 357, and an fθ lens 359.

The beam splitter 350a (first beam splitter) splits the laser light output from the laser light source 31 into two. Of the two laser beams split by the beam splitter 350a, one enters the photodetector 60a (first photodetector), and the other enters the beam splitter 350b. That is, the photodetector 60a detects the laser beam split by the beam splitter 350a. The laser light that has entered the beam splitter 350b is further split into two parts, one of which enters the photodetector 60b (second photodetector) and the other that enters the wedge plate 351. That is, the photodetector 60b detects the laser beam split by the beam splitter 350b.

The wedge plate 351 is located in front of the acousto-optic element 353 (on the laser light source 31 side). The wedge plate 351 deflects the laser beam so that the optical path of the primary light in the acousto-optic element 353 becomes parallel to the light incident on the acousto-optic element 353.

The laser light input to the optical system 35 passes through the wedge plate 351 and then is input to the acousto-optic element 353. The acousto-optic element 353 is an example of a diffractive deflection element. The acousto-optic element 353 is an optical element that uses a piezoelectric element to vibrate a crystal through which laser light can pass, thereby forming periodic fluctuations in the refractive index (contraction waves) in the crystal, and using the compression waves as a diffraction grating. It is.

The grating width of the diffraction grating in the acousto-optic element 353 is adjusted by the vibration frequency applied to the crystal. By adjusting the grating width, the diffraction angle (diffraction direction) of the laser beam can be changed to an arbitrary angle according to Bragg's law. When the angle of the diffraction grating formed in the crystal with respect to the lattice plane (that is, the Bragg angle) is θ, the diffraction angle is 2θ. The vibration frequency applied to the crystal of the acousto-optic element 353 is changed based on a control signal from the control unit 22. That is, the diffraction angle of the acousto-optic element 353 is changed based on a command from the control unit 22.

The beam expander 355 expands the beam diameter of the laser beam output from the acousto-optic element 353 to a required diameter. Beam expander 355 is composed of multiple lenses.

The galvano scanner 357 is a mechanism that swings the laser beam output from the beam expander 355 in the X-axis direction and the Y-axis direction. The galvano scanner 357 includes a first galvano mirror 357a and a second galvano mirror 357b. The first galvano mirror 357a has a reflective surface parallel to the Y-axis, and is rotated within a predetermined angle range about an axis extending in the Y-axis direction. The second galvanometer mirror 357b has a reflective surface parallel to the Z-axis, and is rotated within a predetermined angle range about an axis extending in the Z-axis direction. The laser beam output from the beam expander 355 is first reflected by the second galvanometer mirror 357b, and then reflected by the first galvanometer mirror 357a. The driving of the first galvano mirror 357a and the second galvano mirror 357b is controlled by the control unit 22.

The control unit 22 scans the base material W in the X-axis direction with laser light by driving the first galvano mirror 357a. Further, the control unit 22 can move the position of the laser beam on the base material W in the Y-axis direction by driving the second galvanometer mirror 357b. The galvano scanner 357 is an example of a scanning section. Note that the scanning section may include a polygon mirror instead of the galvano scanner 357. Furthermore, scanning in the X-axis direction may be performed by moving the base material W in the X-axis direction with respect to the laser beam.

The fθ lens 359 is located between the galvano scanner 357 and the base material W on the optical path of the laser beam. The fθ lens 359 focuses the beam diameter of the laser light output from the galvano scanner 357 to a desired beam diameter. Further, the fθ lens 359 converts the constant angular velocity movement of the galvano scanner 357 into uniform velocity scanning of the laser beam on the plane of the base material W.

FIG. 4 is a cross-sectional view schematically showing the configuration of the photodetectors 60a and 60b. The light detection units 60a and 60b each include a diffusion plate 61 (diffusion unit) and a camera 63 that images the laser light L1 diffused by the diffusion plate 61.

The diffuser plate 61 diffuses the laser beam L1 while maintaining the shape of the intensity distribution of the laser beam L1. The diffuser plate 61 is made of ground glass with uniform irregularities formed on its surface by, for example, sandblasting. By configuring the diffusion plate 61 with frosted glass, it is possible to easily diffuse the laser beam L1 uniformly. Note that the diffusion plate 61 may be a light-transmitting plate containing a diffusion agent. Moreover, the diffusion plate 61 may have a microlens array so that the spread angle and shape of the laser beam L1 can be controlled.

Camera 63 has an image sensor 631 and a cover glass 633. The image sensor 631 images the laser light L1 diffused by the diffuser plate 61. The image sensor 631 is preferably a two-dimensional image sensor including a CMOS sensor or a CCD sensor. However, the image sensor 631 may be a one-dimensional image sensor. The cover glass 633 is located in front of the image sensor 631. That is, the cover glass 633 is located between the diffusion plate 61 and the image sensor 631.

Camera 63 has a housing 635. The housing 635 has an opening 636 through which the laser beam L1 passes. Image sensor 631 is located within housing 635. The cover glass 633 closes the opening 636 of the housing 635. The cover glass 633 seals the image sensor 631 within the housing 635 by closing the opening 636.

The housing 635 has a cylindrical portion 637. The cylindrical portion 637 has a cylindrical shape through which the laser beam L1 passes. Diffusion plate 61 is attached within cylindrical portion 637. That is, the diffusion plate 61 is attached to the housing 635 of the camera 63. Thereby, the diffuser plate 61 and camera 63 can be handled as one.

As shown in FIG. 4, the laser beam L1 incident on the diffuser plate 61 is diffused by the diffuser plate 61, passes through the inside of the cylinder 637, passes through the cover glass 633, and enters the image sensor 631. . That is, the image sensor 631 images the laser light L1 that has passed through the cover glass 633.

FIG. 5 is a diagram showing a laser beam image IM1 acquired by the photodetector 60a and a luminance distribution at a position indicated by a broken line in the image IM1. As shown in FIG. 5, since the laser beam L1 is diffused by the diffusion plate 61, it has a spread compared to before diffusion. The control unit 22 calculates the center position of the laser beam L1 from the brightness distribution in this image IM1. Specifically, the position of the peak of brightness, the center of gravity of positional brightness, or the center position of the spread of laser light L1 in image IM1 may be calculated as the center position of laser light L1.

In this embodiment, as shown in FIG. 3, the laser light output from the laser light source 31 is detected by two photodetectors 60a and 60b. In this way, the parallelism of the laser beam can be measured based on the positions of the laser beam detected by the two photodetectors 60a and 60b.

FIG. 6 is a diagram showing a photodetector 60c according to a comparative example. FIG. 7 is a diagram showing an image IM2 of laser light acquired by the light detection unit 60c according to the comparative example, and a luminance distribution at a position indicated by a broken line in the image IM2. The light detection section 60c includes a camera 63 like the light detection sections 60a and 60b, but the diffusion plate 61 is omitted. When the laser beam L1 is detected by the photodetector 60c, the reflected laser beam L2 generated by the backside reflection of the laser beam L1 on the cover glass 633 interferes with the original laser beam L1, thereby forming interference fringes shown in the image IM2. may occur. When interference fringes occur, a plurality of peaks appear in the brightness distribution in image IM2, depending on the brightness and darkness of the interference fringes. The form of this interference fringe may vary depending on the incident position and incident angle of the laser beam L1. Therefore, it is difficult to accurately determine the center position of the laser beam L1.

In the photodetectors 60a and 60b of this embodiment, the laser beam L1 is uniformly diffused by the diffusion plate 61. Therefore, the intensity of the reflected laser beam L2, which can cause interference fringes, is lower than when the diffuser plate 61 is not provided. Therefore, as shown in FIG. 5, the generation of interference fringes is suppressed. Further, as is clear from a comparison between FIGS. 5 and 7, although the Gaussian peak is lowered by the diffusion plate 61, the distribution maintains the Gaussian shape. Therefore, since the peak can be easily detected, the center position of the laser beam can be determined with high accuracy.

Further, as the laser light L1 is spread by the diffuser plate 61, the power density of the laser light L1 irradiated onto the image sensor 631 also decreases. For this reason, it is possible to prevent the image sensor 631 from exceeding the threshold value Th1 that may cause damage, and it is also possible to adjust a higher intensity laser.

Note that another method for attenuating the intensity of laser light is to use an ND filter. However, there is a possibility that interference fringes or optical axis shift may occur due to the use of the ND filter. Therefore, by using the diffuser plate 61, the position of the laser beam can be specified with higher precision than when using an ND filter.

<2. Modified example>
Although the embodiments have been described above, the present invention is not limited to the above, and various modifications are possible.

In the embodiment described above, the photodetectors 60a and 60b detect laser light within the optical system 35. However, the photodetector may detect the laser beam output from the optical system 35. For example, the photodetector may be placed on or near the stage 42.

The control unit 22 may calculate the beam diameter of the laser light L1 before being diffused from the image IM1. For example, if the spread rate by the diffusion plate 61 is known, the beam diameter before diffusion may be determined based on the spread rate and the beam diameter acquired from the image IM1.

The light irradiation device 1 may include an adjustment unit that adjusts the optical axis position, optical axis direction, beam diameter, etc. of the laser light output from the laser light source 31. The adjustment unit may be composed of, for example, a plurality of lenses or mirrors. The control unit 22 may automatically adjust the laser beam by controlling an adjustment unit based on the detection results by the photodetectors 60a and 60b.

Although this invention has been described in detail, the above description is illustrative in all aspects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be envisaged without departing from the scope of the invention. The configurations described in each of the above embodiments and modified examples can be appropriately combined or omitted as long as they do not contradict each other.

1 Light irradiation device 18 Light irradiation section 22 Control section (center position calculation section)
31 Laser light source 35 Optical system 42 Stage (holding part)
60a Photodetector (first photodetector)
60b Photodetector (second photodetector)
61 Diffusion plate (diffusion part)
63 Camera 350a Beam splitter (first beam splitter)
350b beam splitter (second beam splitter)
631 Image sensor 633 Cover glass 635 Housing 636 Opening

Claims (10)

A photodetection device that detects laser light,
a diffusion section that diffuses the laser beam while maintaining the shape of the intensity distribution of the incident laser beam;
an image sensor that images the laser light diffused in the diffusion section; and a camera having a cover glass located between the diffusion section and the image sensor;
A photodetection device comprising: The photodetection device according to claim 1,
A photodetection device, wherein the image sensor is a two-dimensional image sensor. The photodetection device according to claim 2,
a center position calculation unit that calculates a center position of the laser beam based on an image acquired by the image sensor;
A photodetection device further comprising: The photodetection device according to any one of claims 1 to 3,
The camera further includes a housing provided with an opening through which the laser light passes,
the image sensor is located within the housing,
The cover glass is a photodetecting device that closes the opening. The photodetection device according to claim 4,
A photodetection device, wherein the diffusion section is attached to the housing. The photodetection device according to any one of claims 1 to 5,
The light detection device, wherein the diffusion section includes frosted glass. The photodetection device according to any one of claims 1 to 5,
The light detection device, wherein the diffusion section includes a microlens array. A light irradiation device,
a holding part that holds the base material;
a laser light source that outputs laser light;
an optical system that guides the laser light output from the laser light source to the base material held by the base material;
at least one photodetector that detects the laser beam;
Equipped with
The at least one photodetector includes:
a diffusion section that diffuses the laser beam while maintaining the shape of the intensity distribution of the incident laser beam;
an image sensor that images the laser light diffused in the diffusion section; and a camera having a cover glass located between the diffusion section and the image sensor;
A light irradiation device having. The light irradiation device according to claim 8,
The optical system is
a first beam splitter that branches the laser light output from the laser light source;
a second beam splitter that splits the laser beam split by the first beam splitter,
The at least one photodetector includes:
a first light detection unit that detects the laser beam split by the first beam splitter;
a second photodetector that detects the laser beam split by the second beam splitter;
A light irradiation device, including: A light detection method for detecting laser light, the method comprising:
a) diffusing the laser beam while maintaining the shape of the intensity distribution of the laser beam;
b) a step of imaging the laser light transmitted through the cover glass after being diffused in step a) with an image sensor;
A light detection method, including:

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