JP2000232245A - Mirror monitor for laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To discriminate the state of a mirror without directly measuring the reflectivity by a method wherein a mirror monitor for laser is constituted into a structure, wherein the entrance side and exit side temperatures of cooling water, which is flowed in the interior of a mirror main body, are respectively detected by temperature sensors and at the same time, a means for deciding the state of the mirror on the basis of a temperature difference between the entrance side temperature and the exit side temperature is provided. SOLUTION: A mirror main body 1 is formed into such a structure that cooling water is flowed from an entrance part 3 toward an exit part 4 in the interior of the mirror main body 1. Therefore, temperature sensors 5 and 6 are respectively provided on the parts 3 and 4, the entrance side temperature Tin of the cooling water and the exit side temperature Tout of the cooling water are respectively detected by the sensors 5 and 6 and signals from both sensors 5 and 6 are inputted in a discriminating means 7 comprising a microcomputer. At this time, a temperature difference (Tout-Tin) between the temperatures Tin and Tout of the cooling water becomes a parameter to indirectly show the degree of the dirtiness of a reflective surface 2, that is, the reflectivity of a mirror. Thereby, the cost of a mirror monitor can be reduced in comparison with the cost of one for directly measuring the reflectivity of the mirror.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for monitoring a laser mirror for reflecting a laser beam.

[0002]

2. Description of the Related Art A mirror for laser is formed by depositing or plating gold or the like on a mirror body made of aluminum or copper to form a reflection surface. . Further, in order to prevent heat loss of the mirror, the mirror is water-cooled by flowing cooling water into the mirror body.

Meanwhile, the reflectance of the mirror decreases with time due to the adhesion of dust and the like, and the energy of the laser beam applied to the workpiece decreases.

Therefore, conventionally, a beam sampler is provided on the optical path of the laser beam reflected by the mirror, the energy of the laser beam extracted by the sampler is detected by a power meter, and the reflectance of the mirror is measured. A system is known in which when this is done, this is reported to encourage maintenance (see JP-A-61-151439).

[0005]

SUMMARY OF THE INVENTION
A beam sampler and a power meter are required, resulting in high costs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a low-cost monitoring device which can determine the state of a mirror without directly measuring the reflectance by paying attention to cooling water flowing through a mirror body.

[0007]

In order to solve the above problems,
The present invention relates to a monitoring device for a laser mirror that reflects a laser beam, a temperature sensor that detects an inlet side temperature and an outlet side temperature of cooling water flowing in the mirror main body, respectively, an inlet side temperature and an outlet side temperature. Determining means for determining the state of the mirror based on the temperature difference between the mirror and the mirror.

When the reflectivity of the mirror decreases, the energy of the laser beam absorbed by the mirror increases accordingly, the temperature of the mirror body increases, and the temperature of the outlet side of the cooling water also increases. Therefore, the temperature difference between the inlet side temperature and the outlet side temperature of the cooling water is a parameter indirectly representing the reflectance of the mirror, and when this temperature difference becomes large, it is determined that the state of the mirror is defective. By notifying this, the maintenance of the mirror can be performed appropriately.

[0009]

FIG. 1 shows a laser mirror for reflecting a laser beam. This mirror is formed by coating gold or the like on a mirror surface 1 of a mirror body 1 made of aluminum or copper by vapor deposition or plating. The reflectance of the laser beam on the reflection surface 2 is 95% in a normal state. That is all.

In the mirror body 1, cooling water flows from the entrance 3 to the exit 4. Then, temperature sensors 5 and 6 composed of thermocouples and the like are provided at the inlet 3 and the outlet 4, respectively, to detect an inlet-side temperature Tin and an outlet-side temperature Tout of the cooling water. The signal is input to a discriminating means 7 comprising a microcomputer.

Here, when the reflectivity of the laser beam decreases due to the attachment of dust and the like to the reflecting surface 2, the energy of the laser beam absorbed by the mirror increases, and the temperature of the mirror body 1 rises, and The water outlet temperature Tout also increases. When the energy of the incident beam was kept constant at 3 KW, the inlet side temperature Tin of the cooling water was kept constant at 21 ° C., and the degree of contamination of the reflecting surface 2 was changed, the energy of the reflected beam and the outlet side temperature Tout of the cooling water were measured. As shown in FIG.
The energy of the reflected beam is 2.9 KW (reflectance about 96.
7%), 2.85 KW (reflectance 95%), 2.8 KW
(Reflectance about 93.3%), 2.75 KW (reflectance about 9
1.7%), Tout is 23 ° C., 26 ° C., respectively.
The temperature reached 28.5 ° C and 29 ° C. Therefore, the temperature difference ΔT (= T) between the cooling water inlet side temperature Tin and the outlet side temperature Tout
(out-Tin) is a parameter that indirectly represents the degree of contamination of the reflection surface 2, that is, the reflectance.

Therefore, in this embodiment, as shown in FIG. 2, the discriminating means 7 calculates the temperature difference ΔT (S1),
Next, it is determined whether or not △ T is equal to or greater than a predetermined first reference value △ T1 (S2). If △ T ≧ △ T1, △ T is △
It is determined whether or not the second reference value ΔT2 set higher than T1 is equal to or greater than (S3). If ΔT1 ≦ ΔT <ΔT2, the alarm 8 is operated at the caution level (S4). Notifies that the mirror is about to be maintained, and ΔT ≧ ΔT
When the number becomes 2, the alarm 8 is operated at the alarm level (S5) to prompt urgent maintenance of the mirror.

Note that even if the reflectance is constant, {T} varies depending on the ambient temperature, Tin, the energy of the incident beam, and the laser usage rate. It is desirable to variably set T1 and ΔT2.

[0014]

As is apparent from the above description, according to the present invention, the state of the mirror is determined based on the temperature difference between the inlet side and the outlet side of the cooling water, so that the reflectivity of the mirror is directly measured. The cost can be reduced compared to the one.

[Brief description of the drawings]

FIG. 1 shows an example of the device of the present invention.

FIG. 2 is a flowchart showing a discrimination processing program by a discrimination means.

FIG. 3 is a graph showing the relationship between the reflectance and the outlet temperature of the cooling water.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Mirror main body 2 Reflecting surface 3 Inlet part 4 Outlet part 5, 6 Temperature sensor 7 Judgment means

Claims (1)

[Claims] 1. A monitoring device for a laser mirror for reflecting a laser beam, comprising: a temperature sensor for detecting an inlet side temperature and an outlet side temperature of cooling water flowing in a mirror main body; and an inlet side temperature and an outlet side. A determination unit configured to determine a state of the mirror based on a temperature difference from a temperature; and a monitoring device for a laser mirror.