JPH0744386Y2 - Laser beam processing optical system with uniform intensity - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention relates to an intensity homogenizing laser beam processing optical system, and particularly, to an intensity distribution for transforming Gaussian beam light transmitted through a tetrahedral prism into a uniform intensity distribution. Intensity homogenizing laser beam processing optical system.

[Conventional technology]

Heretofore, many techniques have been proposed for making the beam intensity of laser light uniform. The method using a four-sided prism is one of them. As shown in FIG. 5, the method using this four-sided prism is such that the laser beam 1 which is a Gaussian beam whose intensity distribution is shown by the curve A is
Are incident so that their optical axes coincide with each other and are divided into four. At this time, the laser light with high intensity near the optical axis 8 is A1
While refracting away from the optical axis 8 as shown in Fig. 3, the laser light with small intensity at the skirt of the Gaussian beam at the hem is opposite to the optical axis as shown at A2. Refract. In this way, the laser light divided into four parts by the four-sided prism is made up of the inclined surface (side surface) of the four-sided prism and the surface perpendicular to the optical axis of the incident laser light, by overlapping the weak and strong parts. At a distance L uniquely determined by the incident angle θ and the beam diameter 2a of the incident laser light, it is converted into laser light having a uniform intensity distribution B.

FIG. 6 shows each laser beam 1 and the tetrahedral prism 2 viewed in the optical axis direction.
And C is a combined uniform (square) square beam image (composite image).

The composite image C is an optical communication (Opt.Commu
n.) 48,1983,44-46, the uniformity is best when one side is 1.1a, which is 1.1 times the Gaussian beam radius a.

[Problems to be solved by the device]

In the uniform beam optical system using only the conventional four-sided prism described above, the Gaussian beam is used as the incident light. When this Gaussian beam is to be extracted from the laser oscillator, it is usually extracted as light with the highest coherency called TEM ₀₀ mode, so the incident light has excellent coherence. Therefore, in the uniform beam optical system using the four-sided prism, since the four-divided light with high coherency is superposed, there is a problem that interference fringes always appear on the uniform beam. This is inevitable in principle.

FIG. 7 is a diagram showing the pattern of the interference fringes, and a large number of the interference fringes are arranged in # -type in the X and Y directions at intervals of λ / 2sinθ. Where λ is the wavelength of the incident laser light, and the incident angle θ is 90 ° or less. This can be understood by considering that there are two sets of ordinary rooftop prisms, each of which is arranged at an angle of 90 °.

Therefore, the present invention is intended to solve such problems of the conventional ones, and to provide an optical system for processing an intensity uniformized laser beam in which interference fringes do not appear on a uniform beam.

[Means for Solving the Problems]

The present invention has a structure that is moved according to the interval of the interference fringes of the composite image in order to eliminate the nonuniformity caused by the interference fringes generated on the composite image.

That is, according to the present invention, a laser light source that outputs a Gaussian beam, a four-sided prism that refracts the Gaussian beam and irradiates a combined rectangular beam with a uniform beam intensity on a workpiece, and the four-sided prism when viewed from the four-sided prism are used. In a laser beam processing optical system having a total reflection mirror arranged on the side of a workpiece and guiding the combined square beam onto the workpiece, the interference of the combined square beam on the workpiece by the combined square beam. An intensity-uniformized laser beam processing optical system is provided which has a means for vibrating the total reflection mirror so as to oscillate with an amplitude corresponding to the interval between stripes.

[Principle of device]

FIG. 1 is a block diagram for explaining the principle of the present invention. A laser beam emitted as a Gaussian beam from a laser oscillator passes through a four-sided prism 2 as an incident laser beam 1 and enters a total reflection mirror 3 as a beam bender at an angle of 45 °. The reflected light is guided up to 1.1a where the radius of the incident Gaussian beam is a, and is adjusted so that the object 7 comes to that location. At this time, as described above, the interference fringes in the X-axis and Y-axis directions appear on the object 7 as shown in FIG.

Here, the total reflection mirror 3 as a beam bender is vibrated at a high frequency in the Y-axis direction by a linear translator 4, for example. The amplitude when vibrating is such that when a 45 ° four-sided prism is used as in this embodiment, the spacing between the interference fringes is large. You can double it. The point is that the crests of the interference fringes reach the positions of the valleys due to the vibration.

In this way, the interference fringes generated along the X axis repeatedly move in the ± Y axis directions at high speed. Therefore, when viewed in terms of time, it can be regarded as if the interference fringes generated along the X-axis disappeared.

Similarly, if a total reflection mirror capable of vibrating at a high frequency in the X-axis direction is provided, it can be considered that there is no interference fringe generated along the Y-axis this time.

〔Example〕

FIG. 2 is a diagram showing the configuration of FIG. 1 of the present invention. He-Ne laser light (λ = 632.8 μm) was used as the incident laser light 11 having a Gaussian distribution, a tetrahedral prism 12 with an inclination angle of 3 ° was used, and a linear translator of several kH
PZT (Piezo−electric Transduce
r) Use 14 and 16. The incident laser beam 11 passes through the four-sided prism 2 and is bent at a right angle by the total reflection mirror 13 that is vibrated by the PZT 14 for the X axis, and is a beam that vibrates minutely in the −X and + X directions (interference fringe spacing is about 6 μm). Is radiated to the total reflection mirror 15. The total reflection mirror 15 is slightly vibrated by another PZT 16 for the Y axis, and the laser light beam bent at a right angle here is also slightly vibrated in the −Y and + Y directions to irradiate the object 17. To be done. Therefore, neither the interference fringes in the X-axis direction nor the interference fringes in the Y-axis direction are apparent, and it is the same as when the uniform beam light is applied.

In the above, the amplitude of the PZT vibration is structurally limited to about 100 μm, so if more than this is required, the following is done.

FIG. 3 is a diagram showing the configuration of the second embodiment of the present invention.
In this case, the incident laser light 21 is a CO ₂ laser (λ = 10.6 μ
The output light of m) is used, and the galvanometers 24 and 26 are used as linear translators. The four-sided prism 22 and the total reflection mirrors 23 and 25 are the same as those in the first embodiment, and the functions of the apparatus are the same as those in the first embodiment, though there are numerical differences, and are apparently uniform. It is the same as if it was irradiated with a different laser light beam.

In this embodiment, the distance between the interference fringes is about 100 μm, which can be sufficiently dealt with by using the galvanometers 24 and 26. Since this galvanometer can considerably increase the vibration width, it is effective when the distance between the interference fringes is wide and it is necessary to increase the vibration distance for vibrating the composite image.

FIG. 4 shows a front view (a) and a side view (b) of a third embodiment of the present invention. In contrast to the second embodiment, in which the image synthesized by the four-sided prism is moved by using the reflection plate, in this example, the transmission plate 33 having an appropriate thickness d is used, and the inclination θ of the transmission plate 33 is adjusted by the galvanometer. The laser beam passing through the transmissive plate 39 is bent according to the refractive index of the transmissive plate 33, thereby moving the composite image emitted from the four-sided prism 32. At this time, this amount of movement is determined by the thickness d of the inclination θ of the transmission plate 33. This FIG. 4 shows the case where only the X axis is shaken, but if another transmitting plate that shakes the Y axis is added near the transmitting plate 33, the same function as in the second embodiment can be provided. It will be possible.

This embodiment is useful when the inclination angle θ of the tetrahedral prism is relatively large and the distance between the tetrahedral prism and the combined image on the object cannot be long. Another advantage is that the optical axis of the laser beam incident on the four-sided prism and the center of the composite image can be made to substantially coincide with each other. The material of the transmission plate is Zn.
Se (refractive index n = 2.4) or the like may be used.

[Effect of device]

As described above, the present invention is provided with means for swinging the laser light transmitted through the four-sided prism in the X-axis direction and the Y-axis direction according to the intervals of the interference fringes on the surface where a composite image is formed. This has the effect of eliminating the effect of interference fringes on a uniform-intensity beam created by a four-sided prism.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining the principle of the present invention, FIGS. 2 to 4 are block diagrams of an embodiment of the present invention, and FIGS. 5 and 6 show a conventional method for uniformizing the beam intensity. An explanatory diagram and FIG. 7 are explanatory diagrams of interference fringes generated at this time. Explanation of the symbols: 1 ... Incident laser light, 2 ... Four-sided prism, 3 ... Total reflection mirror, 4 ... Linear translator, 7 ... Object.

Claims (1)

[Scope of utility model registration request] 1. A laser light source for outputting a Gaussian beam, a four-sided prism for refracting the Gaussian beam to irradiate a combined rectangular beam having a uniform beam intensity on a workpiece, and the workpiece as viewed from the four-sided prism. In a laser beam processing optical system having a total reflection mirror that is disposed on the object side and guides the combined square beam onto the workpiece, the combined square beam causes interference fringes generated on the workpiece by the combined square beam. An intensity-uniformized laser beam processing optical system having means for vibrating the total reflection mirror so as to swing with an amplitude corresponding to the interval.