JPH06252484A - Laser beam absorber - Google Patents

Abstract

PURPOSE:To enhance absorption efficiency with a high output laser beam without causing a considerable increase in size and deterioration of durability with regards to a laser beam absorber which attenuates and absorbs a laser beam output from a laser oscillator. CONSTITUTION:As the top of a virtual cone of an inner absorber 2 is positioned outside the top portion of an outer absorber 1, a laser beam which enters a laser beam absorber is not projected to the top of the inner absorber but strikes against the outer peripheral curved plane of the inner absorber. Therefore, this construction makes it possible to protect the tip of the cone from damages induced by a laser beam of high power density and prevent its durability from being degraded. The laser beam 100 enters the outer peripheral curved plane (laser beam absorption plane) of the inner absorber 2 a large incident angle. This incident angle makes it possible to lower energy density from 1/2 to 1/4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser beam absorber that attenuates and absorbs a laser beam emitted from a laser oscillator, and more particularly to a laser beam absorber with improved absorption efficiency.

[0002]

2. Description of the Related Art Generally, a laser beam emitted from a laser oscillator is made incident on a laser beam absorber so as not to leak outside when it is not used for processing.

As a typical example of this laser beam absorber, FIG. 5 shows a liquid cooling type laser beam absorber for CO ₂ laser. The liquid-cooled laser beam absorber includes a laser beam absorbing plate 120 and a beam shield cylinder 11.
It is composed of 0 and 0.

The laser beam absorption plate 120 has a slanted surface having an angle of θ10 (for example, 72 degrees) with respect to the laser beam 100 incident on the laser beam absorber, and the apex angle is located at the center of the laser beam 100. It is a thick-walled conical plate. The laser beam absorbing plate 120 is made of copper having good heat conductivity, and its laser beam irradiation surface (absorption surface) is subjected to chrome black treatment.

The beam shield cylinder 110 is a thick-walled cylinder in which the central portion of the inner peripheral surface thereof is inclined and inclined toward the laser beam absorbing plate 120 side to form a conical shape.
Like the laser beam absorption plate 120, it is made of copper, and its surface (absorption surface) is subjected to blackening chrome treatment.

The laser beam 100 incident on the laser beam absorber is absorbed by the laser beam absorbing plate 120, and the reflected component not absorbed is the beam shield cylinder 1.
The reflected component that is radiated to 10 and is not absorbed by the beam shield cylinder 110 is further radiated to the laser beam absorption plate 120 or the beam shield cylinder 110. After that, the laser beam is repeatedly reflected a plurality of times, and finally has a small output and is emitted to the outside.

A cooling water path 140 is provided in the laser beam absorbing plate 120, and cooling water is constantly supplied to remove the thermal energy absorbed by the laser beam absorbing plate 120. The beam shield cylinder 110 is not water-cooled, and the amount of heat absorbed is transmitted to the laser beam absorption plate 120 by heat conduction. This laser beam absorber is used for a 1 KW class laser.

By the way, when the high-power laser beam 100 is absorbed, the energy density of the absorption surface becomes high, so that the absorption surface is melted, destroyed, or the absorption efficiency is lowered, and the function of the laser beam absorber is stable for a long period of time. Will be difficult to fulfill. In the worst case, the incident laser beam 100 goes back and causes a failure of the optical device or the laser oscillator.

Further, when the absorption efficiency of the laser beam absorber is low, scattered light is emitted from the entrance of the absorber, which poses a serious risk to the temperature rise of the equipment near the laser beam absorber and to humans in the radiation area.

[0010]

In the above laser beam absorber according to the prior art, when a high power beam is incident,
It is necessary to reduce the energy density of the absorption surface, and therefore, it is necessary to reduce the apex angle (angle θ10 of the inclined surface) of the cone of the laser beam absorption plate 120 to make the inclination of the inclined surface steeper. However, the center of the cone is the laser beam 100
Since it is located at the center of the cone, if the apex angle of the cone is made small, the tip of the cone is likely to be damaged by the laser beam having a high power density, which leads to deterioration of durability and absorption efficiency.

Further, in order to deal with a high-power laser beam having a large beam diameter, since the inner diameter of the beam shield cylinder 110 must be widened, the length of the beam shield cylinder 110 becomes long in order to obtain the same number of reflections. The size of the laser beam absorber is inevitable.

The present invention has been made in view of the above points, and does not cause an increase in size and deterioration of durability.
An object of the present invention is to provide a laser beam absorber capable of improving absorption efficiency for a high-power laser beam.

[0013]

According to the present invention, in order to solve the above-mentioned problems, a laser beam absorber for attenuating and absorbing a laser beam emitted from a laser oscillator is formed by using a conical curved surface. An inner absorber that absorbs a laser beam incident on a curved surface, and a laser beam that is provided outside of the inner absorber and has a conical inner peripheral surface that is reflected by the inner absorber without being absorbed by the inner peripheral surface. An outer cylinder absorbent body that absorbs by means of an outer cylinder absorbent body, the apex of a virtual cone of the inner absorbent body being located outside the upper inner diameter of the outer cylinder absorbent body, and the conical curved surface of the inner absorbent body and the outer cylinder. A laser beam absorber is provided, characterized in that the inner peripheral surface of the absorber is configured to form a wedge-shaped angle.

[0014]

The inner absorber of the laser beam absorber is formed by using a conical curved surface and absorbs the laser beam incident on the conical curved surface. The outer cylinder absorber is provided outside the inner absorber and has an inner peripheral surface formed in a conical shape. The inner peripheral surface absorbs the laser beam reflected without being absorbed by the inner absorber.

The apex of the virtual cone of the inner absorber is located outside the upper inner diameter of the outer absorber. Therefore, the laser beam incident on the laser beam absorber hits the slope of the conical curved surface without being projected on the apex of the virtual cone of the inner absorber. Therefore, it is possible to prevent the tip of the cone from being damaged by the laser beam having a high power density to deteriorate the durability, and the absorption efficiency does not decrease.

At this time, if the apex angle of the virtual cone is, for example, 60 degrees or less, the energy density is 1/2 to 1 because of the slope.
It is lowered to / 4. Considering the maximum power and beam diameter expected to be incident, the inclination of the slope of the inner absorber is determined so as to be less than the deterioration threshold of the absorption surface to prevent the deterioration of the absorption surface due to the incidence of a high-power laser beam. Can be reduced.

Although the absorption efficiency decreases as the incident angle increases, the laser beam reflected without being absorbed by the slope of the inner absorber enters the outer cylinder absorber and is scattered by the outer cylinder absorber. . Then, the laser beam reflected by the outer cylinder absorber undergoes multiple reflection between the inner and outer cylinder absorbers,
It is attenuated to an energy density that has almost no effect on the outside. Therefore, the absorption efficiency as a whole is improved. In this way, the laser beam is multiply reflected between the inner absorber and the outer cylinder absorber so that the conical curved surface of the inner absorber and the inner peripheral surface of the outer cylinder absorber form a wedge-shaped angle. It depends on the configuration.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical sectional view schematically showing the structure of the laser beam absorber of the present invention. The laser beam absorber is composed of an outer cylinder absorber 1, an inner absorber 2, a bottom cover 3 and a cooling water passage 4.

The outer cylinder absorber 1 is provided outside the inner absorber 2 so as to house the inner absorber 2, has a substantially cylindrical shape with the upper part of the conical body removed, and has a high thermal conductivity. Composed of copper. The inner peripheral surface is also formed in a conical shape, and the inner peripheral surface has
The absorption layer for the laser beam is formed by the blackened chromium coating. An outer frame 5 is provided further outside the outer cylinder absorber 1 to cover and protect the entire outer cylinder absorber 1. When the outer cylinder absorber 1 and the outer frame 5 are integrally formed, a cooling water passage 41 is formed between them.

The inner absorber 2 is housed and fixed in the outer cylinder absorber 1. The inner absorber 2 has a shape in which a part of a cone is cut off by the inner peripheral surface slope of the outer cylinder absorber 1. Similar to the outer cylinder absorber 1, it is made of copper having a high thermal conductivity, and its outer peripheral curved surface also has an absorption layer for a laser beam due to the chrome black coating, like the inner peripheral surface of the outer cylinder absorber 1. Has been formed. The absorption layer formed by the blackened chromium coating is, for example, 70 to 80% depending on the incident angle with respect to a wavelength of 10.6 μm of a carbon dioxide laser.
Has an absorption rate of. The details of the configurations of the outer cylinder absorber 1 and the inner absorber 2 will be described later.

A bottom cover 3 having a substantially circular plate shape is provided on the bottom side of the outer cylinder absorber 1 and the inner absorber 2, and the bottom cover 3 is provided.
Thus, the outer cylinder absorber 1, the inner absorber 2 and the outer frame 5 are integrally fixed.

The cooling water passage 41 is provided between the outer frame 5 and the outer cylinder absorber 1 as described above, and the cooling water passage 42 is provided inside the inner absorber 2 along the outer peripheral curved surface thereof. Further, the bottom lid 3, the outer cylinder absorber 1 and the inner absorber 2 form cooling water passages 43 and 44. These cooling water channels 41, 42, 43, and 44 communicate with each other to form one cooling water channel 4.

The cooling water entered from the inlet 47 provided at the lower end of the outer frame 5 enters the cooling water passage 42 from the cooling water passage 43 as shown by the arrow in the figure, flows along the outer peripheral curved surface of the inner absorber 2 and The absorber 2 is cooled. The cooling water that has passed through the cooling water passage 42 enters the cooling water passage 44, then enters the cooling water passage 41, flows upward along the outer peripheral surface of the outer cylinder absorber 5, and cools the outer cylinder absorber 5. A coated copper wire 45 is wound around the cooling water passage 41 in a coil shape, and the coated copper wire 45 forms a guide passage 46 between the adjacent coated copper wire 45. The cooling water that has entered the cooling water passage 41 is guided by the guide passage 46 and spirally flows upward, and is discharged from the discharge port 48 provided at the upper end of the outer frame 5.

The cooling water passages 42 provided along the outer peripheral curved surface of the inner absorbent body 2 may be increased in number as needed to enhance the cooling effect of the inner absorbent body 2.

Next, the outer cylinder absorbent body 1 and the inner absorbent body 2 will be modeled and their configurations will be described. FIG. 2 is a diagram modeling FIG. 1. In the figure, the outer cylinder absorber 1 is drawn by modeling its inner peripheral surface, and the inner absorber 2 is modeled by drawing its outer peripheral curved surface. The apex angle of the cone 11 of the outer cylinder absorber 1 is θ1, and the apex angle of the virtual cone 21 of the inner absorber 2 is θ2. The central axis 13 of the cone 11 and the central axis 23 of the virtual cone 21 are parallel to each other.

As described above, the inner absorber 2 has a shape in which a part of the virtual cone 21 is cut off by the inner peripheral surface of the outer cylinder absorber 1. Further, the apex 22 of the virtual cone 21 of the inner absorbent body 2 is located outside the upper surface portion (upper inner diameter) 12 of the outer absorbent body 1. The inner diameter of the upper surface portion 12 of the outer cylinder absorber 1 is set to be, for example, about 1.5 times the beam diameter of the laser beam incident on the upper surface portion 12. Further, the outer peripheral curved surface of the inner absorber 2 and the inner peripheral surface of the outer cylinder absorber 1 form a wedge-shaped space, and the wedge-shaped angle θ3 of the space.
In order to have the above, the apex angles θ1 and θ2 are determined so as to satisfy θ2> θ1.

In this embodiment, since the laser beam having the beam diameter of 27φ is made incident, the inner diameter of the upper surface portion 12 of the outer cylinder absorber 1 is set to 40φ. The apex angle θ1 was set to 7 degrees and the apex angle θ2 was set to 40 degrees.

Next, the operation of the laser beam absorber having the above structure will be described with reference to FIG. As described above, since the apex 22 of the virtual cone 21 of the inner absorber 2 is located outside the upper surface portion 12 of the outer cylinder absorber 1, the laser beam incident on the laser beam absorber is internally absorbed. The inner absorber 2 is not projected onto the apex 22 of the virtual cone 21 of the body 2.
Hit the outer curved surface of. Therefore, it is possible to prevent the tip of the cone (apex 22) from being damaged by the laser beam of high power density to deteriorate the durability, and the absorption efficiency does not decrease.

Let the beam cross-sectional area of the laser beam 100 be A,
When the output is P, the laser beam 100 is incident on the laser beam absorber with an average power density P / A. Since this laser beam 100 is incident on the outer peripheral curved surface (laser beam absorption surface) of the inner absorber 2 at an incident angle of 70 degrees (= 90-40 / 2), the average power density P / A is its cos (70 °).
Go down to the minute. It is known from experimental values and literature values that the chromium black coating layer is less deteriorated if the average power density P / A of the incident laser beam 100 is 400 W / cm ² or less. Therefore, the laser beam absorber of this example has P / A × cos (70 °) <40.
It has durability and reliability even for a laser beam having an average power density P / A satisfying 0 W / cm ² . When a laser beam with a beam diameter of 27φ and 6 KW is incident,
The average power density P / A is about 360 W / cm ² , which is 6
It has sufficient durability and reliability for a KW laser beam, and can sufficiently cope with a high-power laser beam. In general, the higher the power of the laser beam, the higher the component it has, and the power density P / A tends to be averaged.

The components which are not absorbed by the inner absorber 2 and reflected are diffused toward the outer cylinder absorber 1 along the outer peripheral curved surface thereof and are absorbed by the outer cylinder absorber 1. A reflection component is also generated in this outer cylinder absorber 1, but since the inner absorber 2 and the outer cylinder absorber 1 form a wedge-shaped space, the reflection component causes multiple reflection between both and at least 7 times. It reflects more. The absorption rate per time is 70
%, So the reflection component remaining after 7 reflections is 0.3 ⁷
It becomes the following. Therefore, the reflection component emitted to the outside without being absorbed by the laser beam absorber is 0.1% or less,
This is a significant improvement over the conventional 1-0.5%. That is, it is possible to secure a sufficient number of reflections required to absorb the high-power laser beam, and to sufficiently function as the laser beam absorber without increasing the size of the laser beam absorber. Can be fulfilled

FIG. 3 is a diagram showing a second embodiment of the present invention, and is a diagram in which the outer cylinder absorber and the inner absorber are modeled and drawn, as in FIG. This embodiment is different from the first embodiment in that the central axis 13a of the cone 11a of the outer cylinder absorber 1a and the central axis 23a of the cone 21a of the inner absorber 2a are different.
Is the point where and intersect.

In this way, both central axes 11a and 23a
So that the vertical angles θ1, θ2 and θ
The bottom surface of the virtual cone 21a of the inner absorbent body 2a can be made smaller with 3 held at the same angle as in the first embodiment. By reducing the bottom surface of the virtual cone 21a,
The radius of curvature of the outer peripheral curved surface of the inner absorber 2a becomes smaller and the degree of bending becomes stronger, and the incident laser beam becomes more diffused when reflected by the outer peripheral curved surface. As a result, the power density of the laser beam incident on the inner absorber 2a and the outer cylinder absorber 1a is reduced, and the heat load of each can be reduced. The central axis 13a and the central axis 23a
The intersection angle with and is, for example, 0 degree or more and 45 degrees or less. At 45 degrees, the bottom of the virtual cone 21a approaches the bottom of the cone 11a.

FIGS. 4A and 4B are views showing a third embodiment of the present invention. FIG. 4A shows the first example and FIG. 4B shows the second example. The present embodiment is characterized in that both or one of the outer cylinder absorber 1 and the inner absorber 2 is formed of a conical curved surface having inclined surfaces of two or more angles. In FIG. 4A, the inner absorber 2b is configured with two inclination angles θ41 and θ42. That is, with respect to the original inclination angle θ41 of the inner absorber 2b, the inclination is made steeper at the point P1, and the inclination angle is set to θ42. When the inner absorber 2b is formed only with the inclination angle θ41, it becomes as shown by the broken line, and the incident laser beam at that time does not enter a position deeper than the point P2. In the present embodiment, since the tilt angle below the point P1 is set to θ42, the incident laser beam enters deeper to the position of the point P3, and the number of reflections increases and the absorption efficiency improves accordingly.

In FIG. 4B, the outer cylinder absorber 1c is constructed with two inclination angles θ43 and θ44. That is,
With respect to the original inclination angle θ43 of the outer cylinder absorber 2c, point P4
Then, the inclination is made gentle and the inclination angle is set to θ44. When the outer cylinder absorber 1c is formed only with the tilt angle θ43, the outer cylinder absorber 1c is indicated by a broken line, and the incident laser beam at that time does not enter a position deeper than the point P5. In this embodiment, the point P
Since the inclination angle below 4 is set to θ44, the incident laser beam can enter a deeper position, and the number of reflections is increased correspondingly, and the absorption efficiency is also improved.

In FIG. 4, either the inner absorber or the outer cylinder absorber is formed of a conical surface having two inclined surfaces, but the conical surface having three or more inclined surfaces. You may comprise. Further, both the inner absorber and the outer cylinder absorber may be configured by a conical curved surface having two or more inclined surfaces.

In the above description, the outer peripheral curved surface of the inner absorber 2 is subjected to the blackening chrome treatment to form the laser beam absorbing surface. However, the outer peripheral curved surface is coated with a substance that reflects the laser beam. It may be formed as a laser beam reflecting surface. In that case, the laser beam incident on the inner absorber 2 has its power density reduced at the outer peripheral curved surface thereof, is reflected, and is absorbed by the outer cylinder absorber 1. The reflected component is incident on the outer peripheral curved surface of the inner absorber 2 again, but the power density is reduced each time and reflected, and is sequentially absorbed by the outer cylinder absorber 1. The inner absorber 2 is originally a portion where the heat load tends to be high, but since it does not absorb the laser beam, the inner absorber 2 can be protected from the high heat load.

[0037]

As described above, in the present invention, the apex of the virtual cone of the inner absorbent body is located outside the upper inner diameter of the outer absorbent body. Therefore, the laser beam incident on the laser beam absorber hits the slope of the conical curved surface without being projected on the apex of the virtual cone of the inner absorber. Therefore, it is possible to prevent the cone tip from being damaged by the laser beam having the high power density and the durability from being deteriorated.

Since the laser beam is incident on the slope of the conical curved surface of the inner absorber, the energy density can be reduced to 1/2 to 1/4 depending on the incident angle. Therefore, the laser beam absorption surface can maintain its durability and reliability even for a high-power laser beam.

Further, since the conical curved surface of the inner absorber and the inner peripheral surface of the outer absorber form a wedge-shaped angle, the laser beam reflected without being absorbed by the slope of the inner absorber is , Multiple reflection occurs between the inner absorber and the outer cylinder absorber, and the energy density is attenuated to such an extent that it hardly affects the outside. That is, it is possible to secure a sufficient number of reflections required to absorb the high-power laser beam, and significantly improve the overall absorption efficiency without increasing the size of the laser beam absorber. be able to.

[Brief description of drawings]

FIG. 1 is a vertical sectional view schematically showing the configuration of a laser beam absorber of the present invention.

FIG. 2 is a diagram modeling FIG. 1;

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing a third embodiment of the present invention.

FIG. 5 is a diagram showing a liquid-cooled laser beam absorber for a CO ₂ laser.

[Explanation of symbols]

 1, 1a, 1b, 1c Outer cylinder absorber 2, 2a, 2b, 2c Inner absorber 3 Bottom lid 4 Coolant flow passage 5 Outer frame 11, 11a Cone 22, 22a Virtual cone

Claims (6)

[Claims] 1. A laser beam absorber that attenuates and absorbs a laser beam emitted from a laser oscillator; an inner absorber that is formed by using a conical curved surface and absorbs the laser beam incident on the conical curved surface; An outer cylinder absorber that is provided outside the inner absorber, has an inner peripheral surface formed in a conical shape, and absorbs a laser beam reflected without being absorbed by the inner absorber by the inner peripheral surface; The apex of the virtual cone of the absorber is located outside the upper inner diameter of the outer cylinder absorber, and the conical curved surface of the inner absorber and the inner peripheral surface of the outer cylinder absorber form a wedge-shaped angle. A laser beam absorber having the above-mentioned configuration. 2. The laser beam absorber according to claim 1, wherein a central axis of the inner absorber and a central axis of the outer cylinder absorber are parallel to each other. 3. The laser beam absorber according to claim 1, wherein a central axis of the inner absorber and a central axis of the outer cylinder absorber intersect with each other. 4. The laser beam absorber according to claim 1, wherein the laser beam absorbing surface of the inner absorber is coated with a substance that reflects the laser beam. 5. The laser beam absorber according to claim 1, wherein both or one of the inner absorber and the outer cylinder absorber is formed of a conical curved surface having inclined surfaces at two or more angles. . 6. The laser beam absorber according to claim 1, wherein a cooling liquid flow path is provided along the laser beam absorption surfaces of the inner absorber and the outer cylinder absorber.