Optical equipment and laser processing heads

Abstract

To provide an optical device capable of suppressing damage of an optical element.SOLUTION: An optical device 1 comprises a diffractive optical element 10, a first translucent member 20, and a holder 30. The first translucent member 20 is provided on a one surface 11 side of the diffractive optical element 10. The holder 30 holds the diffractive optical element 10 and the first translucent member 20. The first translucent member 20 forms at least a part of a sealed structure for hermetically sealing the one surface 11 of the diffractive optical element 10.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to an optical device.

Background Art

[0002] In a conventional optical device, a technique related to an optical element fixed to a holder is disclosed in, for example, Japanese Patent Laid-Open No. 1988-74003 (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional optical device, since the optical element is exposed to the atmosphere, dust and the like easily adhere to the surface of the optical element. And due to the influence of such dust and the like, when a laser irradiates the optical element, a situation has occurred in which the surface of the optical element is easily damaged.

[0005] An object of the present invention is to provide an optical device capable of suppressing damage to an optical element.

Means for Solving the Problems

[0006] According to one aspect of the present invention, Lasers enter and exit. a diffractive optical element, a first light-transmitting member provided on one surface side of the diffractive optical element, a holder that holds the diffractive optical element and the first light-transmitting member, metal and A second light-transmitting member is provided on the other side of the diffractive optical element, which is opposite to the one side of the diffractive optical element. are provided, the first light-transmitting member forms at least a part of a sealing structure that seals the one surface of the diffractive optical element Occasionally, The one surface of the diffractive optical element is oriented in the direction from which the laser is incident or in the direction from which the laser is emitted. We can provide optical equipment.

[0007] According to one aspect of the present invention, Lasers enter and exit. Diffractive optical elements and A first light-transmitting member provided on one side of the diffractive optical element, The diffractive optical element and the first light-transmitting member are held together. metal Equipped with a holder, The holder has a holding portion formed therein for holding the diffractive optical element and the first light-transmitting member. The holding portion has a cylindrical inner diameter portion, a through hole having an inner diameter smaller than the inner diameter portion, and a stepped surface provided between the inner diameter portion and the through hole. The diffractive optical element is arranged in the inner diameter portion. The first light-transmitting member is further provided with a pressing portion that presses it toward the stepped surface. picture, The one surface of the diffractive optical element is oriented in the direction from which the laser is incident or in the direction from which the laser is emitted. We can provide optical equipment. Furthermore, according to one aspect of the present invention, a laser processing head equipped with any of the above-described optical devices can be provided. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to provide an optical device that can suppress damage to optical elements. [Brief explanation of the drawing]

[0009] [Figure 1] This is a perspective view of a laser processing head. [Figure 2] This is a perspective view of the optical device after assembly. [Figure 3] This is a cross-sectional view of the optical device before assembly. [Figure 4] This is a cross-sectional view of the optical device after assembly. [Figure 5] This is a plan view of the optical device after assembly. [Modes for carrying out the invention]

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In all the drawings, similar components are denoted by similar reference numerals, and the description thereof will be omitted as appropriate.

[0011] [Embodiment] FIG. 1 is a perspective view of the laser processing head 100. FIG. 2 is a perspective view of the optical device 1 after assembly. As one aspect of the embodiment, a fiber laser is attached to the laser processing head 100. As one aspect of the embodiment, the laser processing head 100 is not provided with a light source. As one aspect of the embodiment, the optical device 1 is fitted into the laser processing head 100 (part A in FIG. 1). As one aspect of the embodiment, the optical device 1 is in a cartridge shape that can be removed from the laser processing head 100 (part A in FIG. 1).

[0012] FIG. 3 is a cross-sectional view of the optical device 1 before assembly. FIG. 4 is a cross-sectional view of the optical device 1 after assembly. FIG. 5 is a plan view of the optical device 1 after assembly. The optical device 1 will be described using FIGS. 3 to 5. The incident direction DR1 shown in FIGS. 3 and 4 indicates the incident direction of the laser beam emitted from a light source (not shown).

[0013] As shown in FIG. 3, the optical device 1 includes a diffractive optical element 10, a first light-transmitting member 20, a holder 30, a pressing portion 40, a first spacer 50, a second light-transmitting member 60, and a second spacer 70.

[0014] (Diffractive Optical Element 10) In the embodiment, the diffractive optical element 10 is a DOE (Diffractive Optical Element). The diffractive optical element 10 is used for beam shaping, branching, etc. of the laser beam. By changing the diffractive optical element 10 to various types during laser processing, the laser beam can be changed to various beam patterns.

[0015] In this embodiment, the diffractive optical element 10 has a disc-shaped form. The diffractive optical element 10 includes one face 11 and another face 12. The one face 11 and the other face 12 are opposite each other. In one aspect of this embodiment, the one face 11 faces the direction from which the laser is incident. The other face 12 faces the direction from which the laser is emitted (=incident direction DR1). DR2 is the radial direction of the diffractive optical element 10. DR3 is the thickness direction of the diffractive optical element 10.

[0016] The diffractive optical element 10 includes an anti-reflective layer 14. The anti-reflective layer 14 suppresses the reflection of the laser beam that strikes the diffractive optical element 10. The anti-reflective layer 14 is provided on one surface 11 and the other surface 12.

[0017] (First light-transmitting member 20) In this embodiment, the first light-transmitting member 20 has a disc-like shape. The first light-transmitting member 20 is provided on one side 11 of the diffractive optical element 10. In this embodiment, the first light-transmitting member 20 is, for example, a glass member. The first light-transmitting member 20 is at least part of a sealing structure that seals one side 11 of the diffractive optical element 10. The first light-transmitting member 20 is positioned to cover one side 11 of the diffractive optical element 10 so that it is not exposed to the atmosphere. The first light-transmitting member 20 is provided between the first spacer 50 and the pressing portion 40.

[0018] The first light-transmitting member 20 includes an anti-reflective layer 22. The anti-reflective layer 22 suppresses the reflection of the laser beam that strikes the first light-transmitting member 20. In this embodiment, the anti-reflective layer 22 is provided on both sides of the first light-transmitting member 20.

[0019] The first spacer 50 is provided between the diffractive optical element 10 and the first light-transmitting member 20. After the assembly of the optical device 1, the first spacer 50 is in contact with one surface 11 of the diffractive optical element 10 and the first light-transmitting member 20.

[0020] (First spacer 50) In the embodiment, the first spacer 50 has a disc shape. The first spacer 50 has a through hole that penetrates in the thickness direction DR3. The first spacer 50 has an annular shape, that is, a shape along the edge of a circle. However, the first spacer 50 may have a shape along the edge of a polygon. In the embodiment, the first spacer 50 plays a role in preventing the diffractive optical element 10 and the first light-transmitting member 20 from coming into contact. In the embodiment, the first spacer 50 is made of metal. The first spacer 50 may be made of, for example, SUS (Stainless Used Steel) or aluminum.

[0021] (Second light-transmitting member 60) In this embodiment, the second light-transmitting member 60 has a disc-shaped form. The second light-transmitting member 60 is provided on the other side 12 of the diffractive optical element 10, opposite to one side 11. In this embodiment, the second light-transmitting member 60 is, for example, a glass member. The second light-transmitting member 60 is at least part of a sealing structure that seals the other side 12 of the diffractive optical element 10. The second light-transmitting member 60 is positioned to cover the other side 12 of the diffractive optical element 10 so that it is not exposed to the atmosphere. The second light-transmitting member 60 is provided between the second spacer 70 and the holder 30 (= stepped surface 312a).

[0022] The second light-transmitting member 60 includes an anti-reflective layer 61. The anti-reflective layer 61 suppresses the reflection of the laser beam that strikes the second light-transmitting member 60. In this embodiment, the anti-reflective layer 61 is provided on both sides of the second light-transmitting member 60. In this embodiment, the second light-transmitting member 60 may be the same component as the first light-transmitting member 20.

[0023] (Second spacer 70) The second spacer 70 is provided between the diffractive optical element 10 and the second light-transmitting member 60. In this embodiment, the second spacer 70 has a disc shape. The second spacer 70 has a through hole that penetrates in the thickness direction DR3. The second spacer 70 has an annular shape, that is, a shape along the edge of a circle. However, the second spacer 70 may have a shape along the edge of a polygon. In this embodiment, the second spacer 70 plays a role in preventing the diffractive optical element 10 and the second light-transmitting member 60 from coming into contact. In this embodiment, the second spacer 70 is made of metal. For example, the second spacer 70 may be made of SUS (Stainless Used Steel) or aluminum. In this embodiment, the second spacer 70 may be the same part as the first spacer 50.

[0024] (Holder 30) The holder 30 holds the diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70. In this embodiment, the holder 30 is made of metal.

[0025] The holder 30 includes a main body portion 31, a front plate portion 32, and a threaded portion 33. A holding portion 312 is formed on the main body portion 31 (=holder 30). After the assembly of the optical device 1, the holding portion 312 holds (houses) the diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70. The holding portion 312 has a cylindrical inner diameter portion 312c, a through hole 312b having an inner diameter smaller than the inner diameter portion 312c, and a stepped surface 312a.

[0026] In this embodiment, the inner diameter portion 312c has a cylindrical shape. In this embodiment, the diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70 are arranged in the inner diameter portion 312c. The inner diameter of the through hole 312b is smaller than the inner diameter of the inner diameter portion 312c. The diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70 are arranged on the outside of the through hole 312b in the radial direction DR2. In this embodiment, the inner diameter of the through hole 312b is smaller than the outer diameter of the diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70. The through hole 312b allows the laser to pass through. The stepped surface 312a is provided between the inner diameter portion 312c and the through hole 312b. The inner diameter portion 312c, the stepped surface 312a, and the through hole 312b are continuous.

[0027] The front plate portion 32 is provided on the main body portion 31. The front plate portion 32 has a plate-like shape. The length of the front plate portion 32 in the thickness direction DR3 is greater than the length of the main body portion 31 in the thickness direction DR3. The front plate portion 32 serves to make it easier to remove the optical device 1 from the laser processing head 100.

[0028] The threaded portion 33 is attached to the front plate portion 32. By attaching the threaded portion 33 to the main body of the laser processing head 100, the optical device 1 is fixed to the main body of the laser processing head 100.

[0029] (Pressing part 40) The pressing portion 40 presses the first light-transmitting member 20 toward the stepped surface 312a. The pressing portion 40 includes a cover portion 41, a bolt 42, an elastic member 43, and a plate-shaped member 44.

[0030] The cover portion 41 is positioned to cover the holding portion 312 (=inner diameter portion 312c). The cover portion 41 has a plate-like shape. The cover portion 41 has a rectangular outer shape. The cover portion 41 has a cover hole 411 that penetrates the cover portion 41 in the thickness direction DR3. In this embodiment, the inner diameter of the cover hole 411 is smaller than the outer diameter of the diffractive optical element 10, the first light-transmitting member 20, the first spacer 50, the second light-transmitting member 60, and the second spacer 70. The cover portion 41 has four holes. Bolts 42 are provided in four locations. The four bolts 42 are inserted into the four corresponding holes, fixing the cover portion 41 to the holder 30.

[0031] The elastic member 43 is provided between the cover portion 41 and the first light-transmitting member 20. The elastic member 43 is provided between the cover portion 41 and the plate-shaped member 44. After the assembly of the optical device 1, the elastic member 43 is in contact with the cover portion 41 and the plate-shaped member 44.

[0032] The elastic member 43 generates an elastic force in the thickness direction DR3. In this embodiment, the elastic member 43 has a through hole that penetrates in the thickness direction DR3. The elastic member 43 is made of metal, for example. In this embodiment, the elastic member 43 is a washer having a disc shape.

[0033] The plate-shaped member 44 is provided between the elastic member 43 and the first light-transmitting member 20. After the assembly of the optical device 1, the plate-shaped member 44 is in contact with the elastic member 43 and the first light-transmitting member 20. The plate-shaped member 44 has a through hole formed therein in the thickness direction DR3. The plate-shaped member 44 is made of metal, for example. In this embodiment, the plate-shaped member 44 is a shim having a disc shape. After the assembly of the optical device 1, the plate-shaped member 44 and the elastic member 43 are held (housed) in the holding part 312.

[0034] By tightening the bolt 42, the cover portion 41 presses against the elastic member 43, the elastic member 43 presses against the plate-shaped member 44, and the plate-shaped member 44 presses against the first light-transmitting member 20. Furthermore, by tightening the bolt 42, the diffractive optical element 10, which is pressed against the first light-transmitting member 20 (first spacer 50), presses against the second spacer 70, and the second spacer 70 presses the second light-transmitting member 60 toward the stepped surface 312a. As a result, a structure is formed in which the second light-transmitting member 60 covers the diffractive optical element 10 from the other side 12 as well, i.e., a sealed structure. Therefore, a sealed structure is formed on both sides of the diffractive optical element 10 by the second light-transmitting member 60 and the first light-transmitting member 20.

[0035] The plate-shaped member 44 (=pressing part 40) presses the first light-transmitting member 20 toward the stepped surface 312a of the holder 30. The plate-shaped member 44 (=pressing part 40) presses the first light-transmitting member 20 toward the diffractive optical element 10 (or the first spacer 50).

[0036] After assembly of the optical device 1, the cover portion 41, elastic member 43 (washer), plate-shaped member 44 (shim), first light-transmitting member 20, first spacer 50, diffractive optical element 10, second spacer 70, second light-transmitting member 60, and holder 30 are arranged in this order in the thickness direction DR3.

[0037] In this embodiment, the laser beam passes through the cover hole 411 of the cover portion 41, the through hole of the elastic member 43 (washer), the through hole of the plate-shaped member 44 (shim), the first light-transmitting member 20, the through hole of the first spacer 50, the diffractive optical element 10, the through hole of the second spacer 70, the second light-transmitting member 60, and the through hole 312b of the holder 30 in this order.

[0038] (Effects and Benefits) In conventional optical systems, the laser device, including the laser processing head, is installed inside the factory. Furthermore, the diffractive optical element incorporated into the optical device on the laser processing head is not covered by protective glass or similar, and is exposed to the atmosphere. Therefore, it is an environment where dust and other particles easily adhere to the diffractive optical element.

[0039] When dust, particles, or other debris adhered to the surface of a diffractive optical element, and a laser beam was shone upon the element, heat concentration caused damage to the surface of the diffractive optical element.

[0040] When the surface of a diffractive optical element is damaged, the amount of heat absorbed by the diffractive optical element increases, resulting in a greater thermal lensing effect. This reduces the transmittance of the laser beam, which in turn reduces the output of the processing laser beam irradiated onto the workpiece, sometimes leading to processing defects in the workpiece.

[0041] A feature of this invention is that a first light-transmitting member 20 is provided on one side 11 of the diffractive optical element 10, and the first light-transmitting member 20 is at least part of a sealed structure that seals one side 11 of the diffractive optical element 10.

[0042] By covering the diffractive optical element 10 with the first light-transmitting member 20 (glass member), even if the optical device 1 is installed in a factory, the adhesion of dust and other particles to the surface of the diffractive optical element 10 can be suppressed. This suppresses heat concentration to the diffractive optical element 10. Therefore, damage to the diffractive optical element 10 can be suppressed.

[0043] Since the first light-transmitting member 20 is exposed to the atmosphere, dust and other particles will adhere to its surface. However, compared to the diffractive optical element 10, which has a surface pattern, damage to the surface of the first light-transmitting member 20 is easier to visually inspect. Because damage to the surface of the first light-transmitting member 20 is easier to inspect, the timing for replacing the first light-transmitting member 20 can be easily determined. Therefore, the occurrence of processing defects can be effectively suppressed.

[0044] Furthermore, by suppressing damage to the diffractive optical element 10, the lifespan of the diffractive optical element 10 can be extended. Since the first light-transmitting member 20 is inexpensive compared to the expensive diffractive optical element 10, the maintenance costs of the optical device 1 can be reduced.

[0045] Furthermore, by providing a pressing portion 40 that presses the first light-transmitting member 20 toward the stepped surface 312a, one surface 11 of the diffractive optical element 10 can be effectively sealed with the first light-transmitting member 20. This effectively suppresses the adhesion of dust, dirt, etc. to the surface of the diffractive optical element 10, and thus effectively suppresses damage to the diffractive optical element 10.

[0046] Because the pressing portion 40 includes the cover portion 41, the diffractive optical element 10 and the first light-transmitting member 20 can be effectively held in the holding portion 312. This allows the diffractive optical element 10 and the first light-transmitting member 20 to be stably held in the holder 30.

[0047] The inclusion of an elastic member 43 in the pressing portion 40 allows the first light-transmitting member 20 to be effectively pressed against the diffractive optical element 10. This allows the first light-transmitting member 20 to effectively seal one surface 11 of the diffractive optical element 10. Therefore, damage to the diffractive optical element 10 can be effectively suppressed.

[0048] Furthermore, by including an elastic member 43 in the pressing portion 40, the force with which the first light-transmitting member 20 presses the diffractive optical element 10 can be effectively adjusted.

[0049] Because the pressing portion 40 includes a plate-shaped member 44, the plate-shaped member 44 (=pressing portion 40) can apply uniform surface pressure to the first light-transmitting member 20. Therefore, the plate-shaped member 44 (=pressing portion 40) can effectively press the first light-transmitting member 20 against the diffractive optical element 10.

[0050] By including the anti-reflective layer 22 in the first light-transmitting member 20, the reflection of the laser beam can be effectively suppressed.

[0051] Because the diffractive optical element 10 is disc-shaped, it becomes easier to use general-purpose parts such as washers and shims when constructing the optical device 1, thereby reducing the cost of the optical device 1.

[0052] By providing the first spacer 50, contact between the diffractive optical element 10 and the first light-transmitting member 20 can be suppressed. Therefore, friction between the diffractive optical element 10 and the first light-transmitting member 20 and damage to the diffractive optical element 10 and the first light-transmitting member 20 can be suppressed.

[0053] Because the first spacer 50 is made of metal, the generation of gas caused by the laser hitting the first spacer 50 can be suppressed.

[0054] By providing the second light-transmitting member 60, damage to the diffractive optical element 10 can be suppressed from the other side 12 as well.

[0055] The inclusion of an anti-reflective layer in the second light-transmitting member 60 effectively suppresses the reflection of the laser beam.

[0056] By providing the second spacer 70, contact between the diffractive optical element 10 and the second light-transmitting member 60 can be suppressed. Therefore, friction between the diffractive optical element 10 and the second light-transmitting member 60 and damage to the diffractive optical element 10 and the second light-transmitting member 60 can be suppressed.

[0057] Because the second spacer 70 is made of metal, the generation of gas caused by the laser hitting the second spacer 70 can be suppressed.

[0058] (Other embodiments) The pressing portion 40 can have any configuration as long as it is configured to press the first light-transmitting member 20. For example, it may have a female thread formed on the inside of the inner diameter portion 312c, and a male thread formed on the pressing portion 40 that engages with the female thread, and by rotating the pressing portion 40, the pressing portion 40 advances in the incident direction DR1, and the pressing portion 40 presses the first light-transmitting member 20.

[0059] In one embodiment, the optical device 1 is described as a part of the laser processing head 100, but in another embodiment, the optical device 1 may be configured to include the laser processing head 100 (the optical device 1 may be equal to the laser processing head 100).

[0060] In one embodiment, the first spacer 50 may be omitted, but in this case, it is preferable that the diffractive optical element 10 and the first light-transmitting member 20 are arranged inside the holder 30 so as not to come into contact with each other. For example, the diffractive optical element 10 and the first light-transmitting member 20 may be fixed inside the inner diameter portion 312c, separated from each other (i.e., without contact).

[0061] In another embodiment, the diffractive optical element 10 may have a rectangular shape.

[0062] In another embodiment, one surface 11 may face the direction from which the laser is emitted (=incident direction DR1), and the other surface 12 may face the direction from which the laser is incident.

[0063] The embodiments of the present invention have been described above with reference to the drawings, but these are merely examples of the present invention, and various other configurations can also be adopted. Examples of reference formats are provided below. 1. Diffractive optical element, A first light-transmitting member provided on one side of the diffractive optical element, The holder comprises the diffractive optical element and the first light-transmitting member, An optical device in which the first light-transmitting member is at least part of a sealing structure that seals one surface of the diffractive optical element. 2. The holder has a holding portion formed therein for holding the diffractive optical element and the first light-transmitting member. The holding portion has a cylindrical inner diameter portion, a through hole having an inner diameter smaller than the inner diameter portion, and a stepped surface provided between the inner diameter portion and the through hole. The diffractive optical element is arranged in the inner diameter portion. The optical apparatus according to 1, further comprising a pressing portion for pressing the first light-transmitting member toward the stepped surface. 3. Diffractive optical elements and, A first light-transmitting member provided on one side of the diffractive optical element, The holder comprises the diffractive optical element and the first light-transmitting member, The holder has a holding portion formed therein for holding the diffractive optical element and the first light-transmitting member. The holding portion has a cylindrical inner diameter portion, a through hole having an inner diameter smaller than the inner diameter portion, and a stepped surface provided between the inner diameter portion and the through hole. The diffractive optical element is arranged in the inner diameter portion. An optical device further comprising a pressing portion for pressing the first light-transmitting member toward the stepped surface. 4. The optical apparatus according to 2. or 3., wherein the pressing portion includes a cover portion arranged to cover the holding portion. 5. The optical apparatus according to 4, wherein the pressing portion further includes an elastic member provided between the cover portion and the first light-transmitting member. 6. The optical apparatus according to 5, wherein the pressing portion further includes a plate-shaped member provided between the elastic member and the first light-transmitting member. 7. The optical apparatus according to any one of 1 to 3, wherein the first light-transmitting member includes an anti-reflective layer. 8. The optical device according to any one of 1 to 3, wherein the diffractive optical element has a disc-shaped form. 9. The optical apparatus according to any one of 1 to 3, further comprising a first spacer provided between the diffractive optical element and the first light-transmitting member. 10. The optical apparatus as described in 9, wherein the first spacer is made of metal. 11. The optical apparatus according to any one of 1 to 3, further comprising a second light-transmitting member provided on the other side of the diffractive optical element, which is opposite to the one side of the diffractive optical element. 12. The optical apparatus according to 11, wherein the second light-transmitting member includes an anti-reflective layer. 13. The optical apparatus according to 11, further comprising a second spacer provided between the diffractive optical element and the second light-transmitting member. 14. The optical apparatus described in 13, wherein the second spacer is made of metal. [Explanation of symbols]

[0064] 1 Optical device 10 Diffractive optical elements 11 one side 12 Other side 14 Anti-reflection layer 20 First light-transmitting member 22 Anti-reflection layer 30 holders 31 Main body 32 Front plate part 33 Threaded part 40 Pressing part 41 Cover section 42 volts 43 Elastic members 44 Plate-shaped member 50 First Spacer 60 Second light-transmitting member 61 Anti-reflection layer 70. Second spacer 100 laser processing heads 312 Holding part 312a Stepped surface 312b Through hole 312c inner diameter 411 Cover holes DR1 incident direction DR2 radial direction DR3 Thickness direction

Claims

1. A diffractive optical element into which a laser enters and exits, A first light-transmitting member provided on one side of the diffractive optical element, A metal holder for holding the diffractive optical element and the first light-transmitting member, The diffractive optical element comprises a second light-transmitting member provided on the other side, which is opposite to the one side of the diffractive optical element, The first light-transmitting member is at least part of a sealing structure that seals one surface of the diffractive optical element. An optical device in which one surface of the diffractive optical element is oriented in the direction from which the laser is incident or in the direction from which the laser is emitted.

2. The holder has a holding portion formed therein for holding the diffractive optical element and the first light-transmitting member. The holding portion has a cylindrical inner diameter portion, a through hole having an inner diameter smaller than the inner diameter portion, and a stepped surface provided between the inner diameter portion and the through hole. The diffractive optical element is arranged in the inner diameter portion. The optical apparatus according to claim 1, further comprising a pressing portion for pressing the first light-transmitting member toward the stepped surface.

3. A diffractive optical element into which a laser enters and exits, A first light-transmitting member provided on one side of the diffractive optical element, The device comprises a metal holder for holding the diffractive optical element and the first light-transmitting member, The holder has a holding portion formed therein for holding the diffractive optical element and the first light-transmitting member. The holding portion has a cylindrical inner diameter portion, a through hole having an inner diameter smaller than the inner diameter portion, and a stepped surface provided between the inner diameter portion and the through hole. The diffractive optical element is arranged in the inner diameter portion. The first light-transmitting member is further provided with a pressing portion that presses it toward the stepped surface, An optical device in which one surface of the diffractive optical element is oriented in the direction from which the laser is incident or in the direction from which the laser is emitted.

4. The optical apparatus according to claim 2 or 3, wherein the pressing portion includes a cover portion arranged to cover the holding portion.

5. The optical apparatus according to claim 4, wherein the pressing portion further includes an elastic member provided between the cover portion and the first light-transmitting member.

6. The optical apparatus according to claim 5, wherein the pressing portion further includes a plate-shaped member provided between the elastic member and the first light-transmitting member.

7. The optical apparatus according to any one of claims 1 to 3, wherein the first light-transmitting member includes an anti-reflective layer.

8. The optical apparatus according to any one of claims 1 to 3, wherein the diffractive optical element has a disc-shaped form.

9. The optical apparatus according to any one of claims 1 to 3, further comprising a first spacer provided between the diffractive optical element and the first light-transmitting member.

10. The optical apparatus according to claim 9, wherein the first spacer is made of metal.

11. The optical device according to claim 3, further comprising a second light-transmitting member provided on the other side of the diffractive optical element, which is opposite to the one side of the diffractive optical element.

12. The optical apparatus according to any one of claims 1, 2, and 11, wherein the second light-transmitting member includes an anti-reflective layer.

13. The optical apparatus according to any one of claims 1, 2, and 11, further comprising a second spacer provided between the diffractive optical element and the second light-transmitting member.

14. The optical apparatus according to claim 13, wherein the second spacer is made of metal.

15. A laser processing head comprising the optical device according to any one of claims 1 to 3.

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