JPH02207215A - Multi-branch optical device and beam splitter holder - Google Patents

Abstract

PURPOSE:To correct variance in the branch light intensity of a half-mirror variably and to branch beam intensity at a uniform rate by slanting the reflecting surface of the beam splitter specifically to the optical axis of incident light and also rotating the reflecting surface of the beam splitter around the optical axis of the incident light. CONSTITUTION:The device consists of dielectric multi-layered thin film half- mirrors 7-9 for 45 deg. reflection and beam splitter holders 10-12 which hold the half-mirrors respectively. Then the polarization coordinates (S-P system) of the half-mirror 8 are rotated by an angel PSI to the polarization coordinates (s-p system) of the half-mirror 7 and then the apparent S-polarized component and P-polarized component of light 17 incident on the half-mirror 8 become equal, so that reflected light 19 and transmitted light 20 become equal in beam intensity. Namely, the beam splitter holder 11 is rotated to the beam splitter holder 10 and fixed with an adjusting ring 14 where the reflected light 19 and transmitted light 20 become equal in beam intensity. Consequently, circular polarized incident light 16 can be branched in many directions while the beam diameters and energy distributions are equalized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a multi-branching device for branching laser light, etc., and a beam splitter holder used therein.

2. Description of the Related Art In recent years, with the increase in the output of laser oscillators, a method of branching a laser beam into a plurality of laser beams and simultaneously performing a large number of processes has been frequently used. When splitting a laser beam, a beam splitter (usually referred to as a half mirror hereinafter) that reflects 1/2 of the beam intensity and transmits 1/2 of the beam intensity is generally used. By tilting the reflecting surface of this half mirror at 45 degrees with respect to the optical axis of the laser beam, the transmitted light and the reflected light are split with the same beam diameter, beam intensity, and energy distribution.

The half mirror used is one in which a metal thin film or a dielectric multilayer thin film is formed on a transparent substrate by vacuum deposition.

Metal thin film half mirrors have little change in the polarization components of both reflected and transmitted light with respect to incident light, but because they absorb laser light as high as several percent, they are easily damaged by laser light, and are susceptible to damage from high-power laser light. It is not used as a λ-humirar.

On the other hand, in the case of a dielectric multilayer thin film half mirror, the polarization components of reflected light and transmitted light change with respect to the incident light. In other words, the reflected light has a higher proportion of the S-polarized light component than the incident light, and a smaller proportion of the P-polarized light component. In addition, the transmitted light has a higher proportion of the P polarized light component than the incident light, and a smaller proportion of the S polarized light component. Therefore, the dielectric multilayer thin film half mirror assumes that the incident light is circularly polarized light, and uses a dielectric so that the sum of the P-polarized light and S-polarized light of the reflected light matches the sum of the P-polarized light and S-polarized light of the transmitted light. We design and deposit multilayer thin films.

FIG. 2 is an example showing the polarization components of reflected light and transmitted light when circularly polarized incident light is split by a half mirror. That is, although the transmitted light and reflected light have biased polarization components, their beam intensities are equal. In addition, since the absorption of laser light can be reduced to less than 1%, dielectric multilayer thin film half mirrors can be used as half mirrors for high-output laser light.
is used.

When laser light is branched into three or more branches, the light branched by a dielectric multilayer thin film half mirror (hereinafter abbreviated as half mirror) is branched again using a half mirror.

Hereinafter, a method of multi-branching a laser beam using the above-mentioned conventional half mirror will be explained with reference to the drawings. FIG. 4 is an example of multi-branching of laser light using a conventional half mirror. In FIG. 4, 31 is a laser beam output from an oscillator, and 32, 33 and 34 are half mirrors for branching the laser beam. 35, 36, 37.38 are
This is a neutral density filter (ND filter) for matching the beam intensities of the branched laser beams.

In FIG. 4, a laser beam 31 output from an oscillator is divided into reflected light IR and transmitted light 1T by a half mirror 32.
Branched out. The reflected light IR split by the half mirror 32 is split into the transmitted light I by the half mirror 33 on the same plane.
The light is branched into RI and reflected light IRR. half mirror
The transmitted light 1T branched by 32 is split by a half mirror 34 into transmitted light ITT and reflected light ITR on the same plane.
It is divided into two branches. However, when four laser beams are emitted on the same plane,
- If branched, the branched light IRT, IRR, ], TT.

], the beam intensities of TT do not necessarily match. This is due to the following reason.

First, assuming that the laser beam 31 output from the oscillator is circularly polarized, and using the half mirrors 32, 33, and 34 with the characteristics shown in FIG. 2, for example, the reflected light IR and From FIG. 2, the polarization component of the transmitted light IT is: Reflected light], R: 2/3 (S) + 1. /3 (P) Transmitted light IT becomes 1/3 (S) + 2/3 (P).

Here, (S) and (P) indicate the ratio of S-polarized light and P-polarized light components of the laser beam. Next, when this reflected light IR is split on the same plane by a half mirror 33 with the same characteristics, reflected light IRR 2/3X2/3 (S) +1/3X1
/3 (P) Transmitted light IRT: 2/3xl/3 (S)+1, /3X
It becomes 2/3 (P). Similarly, when the transmitted light IT split by the half mirror 32 is split on the same plane by the half mirror 34 with the same characteristics, the reflected light ITR 2/3X 1/3 (S) +1/3x
2/3 (P) Transmitted light ITT: 2/3x2/3 (S)+2/3x
2/3 (P). Therefore, branch light IRT, IRR, ITT.

The ITR beam intensity ratio is 4:5M5:4. However, here, for simplicity, it is assumed that there is no reflection of light from the back surface of the half mirror.

Furthermore, although it is assumed that the laser beam 31 output from the oscillator is circularly polarized light, if this polarization component changes due to a change in the output of the oscillator, etc., branched light IRT is generated.

The ratio of the beam intensities of IRR,1, TT and ITR is further varied. FIG. 5 shows the laser beam 31 output from the oscillator when a half mirror with the characteristics shown in FIG. 2 is used.
Branched light IRT, IRR, IT for changes in polarization component of
It is a graph obtained by calculation of the ratio of beam intensity of T and ITR.

Further, the above is the ratio of spectral intensity determined from the design value of the half mirror, but in reality, the ratio of spectral intensity will differ from the calculated value due to variations in the film thickness of the dielectric multilayer thin film.

In laser processing, the processing state also changes due to changes in beam intensity. Therefore, when a laser beam is branched into multiple branches, uniformity of the beam intensity of the branched lights is required. Currently, as a countermeasure to this problem, branch optical IRT is used.

Neutral density filters 35, 36, 37, 38 are selectively inserted after IRR, ITT, and ITR, respectively, to obtain uniform beam intensities 39, 40, 44, 42.

Problems to be Solved by the Invention However, as the number of branches increases, the variation in the branched light increases, and when this variation is corrected with a neutral density filter, the loss in beam intensity also increases. For example, in a four-branch optical system (not shown in Figure 4), the loss is 10%.
That's all. Furthermore, when branching high-power laser light, damage to the neutral density filter occurs due to absorption of the laser light.

In view of the above problems, the present invention provides a multi-branching optical device that can variably correct variations in the intensity of branched light of a half mirror, branch the beam intensity at an even ratio, and reduce the loss of beam intensity. It is.

Means for Solving the Problems In order to solve the above problems, the multi-branching optical device of the present invention includes:
The reflective surface of the beam splitter is at 45° with respect to the optical axis of the incident light.
The beam splitter is characterized by having a structure in which the reflecting surface of the beam splitter can be rotated about the optical axis of the incident light.

Further, in the beam splitter holder of the present invention, one of the two cylinders is joined to the side surface of the other cylinder so that the central axis of each cylinder is perpendicular to the side surface of the other cylinder, and the side surface of the cylinder inside the joint part is made hollow. , and the beam splitter is held at the intersection of the central axes of the two cylinders so that the reflecting surface forms an angle of 45 degrees with the central axes of the two cylinders.

Effect of the Invention With the above-described configuration, the present invention rotates the reflecting surface of the beam splitter according to changes in the polarization component of the incident light, thereby changing the beam diameter, beam intensity, and The energy distribution can be made the same and the output ratio can be adjusted, so variations in the intensity of the branched light can be variably corrected, the beam intensity can be split at an even ratio, and the loss of the beam intensity can be reduced.

Further, by joining the beam splitter holder of the present invention, the multi-branch optical device described above can be easily constructed.

EXAMPLE Hereinafter, a multi-branching optical device according to an example of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a multi-branching optical device according to the present invention. Fig. 1(a) shows a beam splitter holder which is a unit that constitutes a multi-branching optical device, and Fig. 1(b) shows a beam splitter holder that is a unit that constitutes a multi-branching optical device. This is a multi-branching optical device that can branch.

In Fig. 1(a), 1 is a 45-degree reflective dielectric multilayer thin film half mirror (beam splitter), and 2 is two cylinders, one of which has its central axis perpendicular to the side surface of the other cylinder. At the same time, the side surface of the cylinder inside the joint part is made hollow, and the reflective surface of the half mirror 1 is placed at the intersection of the central axes of the two cylinders at a 45 degree angle with the central axes of the two cylinders. This is the beam splitter holder held by the holder. Reference numeral 3 denotes incident light that enters the central axis ``2'' of the cylinder holding the half mirror 1. Reference numeral 4 denotes transmitted light that is split by the half mirror 1, and travels parallel to the central axis of the cylinder. 5 is the reflected light branched by the half mirror 1;
It moves along the center axis of the other cylinder. Further, 6 is provided at one end of the cylinder in order to align the central axis of the cylinder holding the half mirror 1 with the optical axis of the incident light, and to fix it by changing the rotational position arbitrarily with the optical axis of the incident light as the central axis. Adjustment ring. Incident light 3 is converted into 2 by half mirror 1.
However, the reflective surface of half mirror 1 splits the incident light beams 3 and 4.
Since the angle is 5 degrees, the transmitted light 4 and the reflected light 5 have the same beam diameter, beam intensity, and energy distribution.

Next, a multi-branching optical device in which three beam splitter holders shown in FIG. 1(a) are combined to split a laser beam into four branches will be described with reference to FIG. 1(b). In FIG. 1 (1)), 7, 8.9 are dielectric multilayer thin film half mirrors for 45-degree reflection, and 10, 11.12 are half mirrors, respectively.
This is the beam splitter holder shown in FIG. 1(a) holding the beams 7, 8, and 9. The beam splitter holder 11 is connected to the cylinder on the reflected light side of the beam splitter holder 10 by an adjustment ring 14 of the beam splitter holder 11, and is rotatable. The beam splitter holder 12 is connected to the cylinder on the transmitted light side of the beam splitter holder 10 by an adjustment ring 15 of the beam splitter holder 12, and is rotatable. 16,17.
Reference numerals 18 denote incident light 2, reflected light, and transmitted light of the half mirror 7, respectively. ]9.20 are the reflected light and transmitted light of the half mirror 8, respectively, and 21.22 are the reflected light and transmitted light of the half mirror 9, respectively.

The branching principle of this embodiment will be explained below.

Incident light 16 is split by half mirror 7 into reflected light 17 and transmitted light 18. For example, if the half mirror 7 has the characteristics shown in Fig. 2 and the incident light 17 is assumed to be circularly polarized, the polarization component of the reflected light 17 is the reflected light 17.2/3 (S) + 1/3 (P) This is shown in Fig. 3 using electrolytic vector coordinates. In Fig. 3, the coordinate system s-p represents the coordinates of polarized light of the half mirror 7, OA represents the electrolytic vector of S-polarized light, OB represents the electrolytic vector of P-polarized light, and OC represents the combined electrolytic vector of S-polarized light and P-polarized light. .

Further, the rotation angle θ is tanθ=1/2. Here, if the coordinate axis is rotated by ψ so that tanθ-1 and the coordinate system in that case is S-P, then the coordinate system S-
The S-polarized light component and the P-polarized light component of the reflected light 17 viewed from P are equal. That is, in FIG. 1(b), if the polarization coordinates of the half mirror 8 (SP system) are rotated by an angle ψ with respect to the polarization coordinates of the half mirror 7 (SP system), the incidence on the half mirror 8 is The apparent S-polarized light component and P-polarized light component of the light 17 are equal, and the reflected light]9 and the transmitted light 20
The beam intensities of will be equal. That is, the beam splitter holder 11 may be rotated relative to the beam splitter holder 10 and fixed using the adjustment ring 14 at a point where the beam intensities of the reflected light 19 and the transmitted light 20 become equal. On a similar principle, the adjusting ring 15 of the beam splitter holder 12
By adjusting and fixing it to the beam splitter holder 10, the beam intensities of the split lights 21 and 22 can be made equal. Incidentally, due to the thickness of the half mirror, the optical axis of the light transmitted through the half mirror 7 is misaligned with the cylindrical center axis of the beam splitter holder 12, but this can be adjusted using an adjustment ring.

Effects of the Invention As described above, in the present invention, the reflective surface of the beam splitter has an inclination of 45 degrees with respect to the optical axis of the incident light, and the reflective surface of the beam splitter can rotate around the optical axis of the incident light. By having this structure, the incident circularly polarized light can be branched into multiple branches with the same beam diameter and energy distribution, and since a neutral density filter is not used, beam loss can be reduced, and the beam intensity can be uniformly split into multiple branches.

Furthermore, not only can the ratio of half mirror spectral intensity due to variations in the film thickness of the dielectric multilayer thin film be corrected, but also the output ratio of reflected light and transmitted light can be adjusted using the same half mirror.

Furthermore, it can be used not only when the incident light of the multi-branching optical device is circularly polarized light, but also when it is other than circularly polarized light, and is particularly effective when the polarization component of the laser beam that is the incident light changes due to changes in output, etc. can.

Furthermore, by using the beam splitter holder of the present invention, the rotation can be easily adjusted.

[Brief explanation of the drawing]

FIG. 1 shows a multi-branch optical device according to an embodiment of the present invention, FIG. 1(a) is a perspective view of a beam splitter holder used in the device, and FIG. A perspective view of the branching optical device. Figure 2 is a characteristic diagram of the polarization components of the reflected light and transmitted light when circularly polarized incident light is split by a half mirror. Figure 3 is the polarization at the electrolytic vector) and le coordinates. FIG. 4 is a configuration diagram of a conventional multi-branching optical device, and FIG. 5 is a beam intensity characteristic diagram of branched light by the conventional multi-branching optical device. 1.7, 8.9... Half mirror (beam splitter), 2, 10, 11.12... Beam splitter holder, 3, 16... Incident light, 4 ,1
8...Transmitted light, 5,17...Reflected light,
19.21...Reflected light, 20.22...
·Transmitted light. Agent's name: Patent attorney Shigetaka Awano Haka 1 name number 51! ! , length (pm) Fig. 10.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000 color type type form type form form is to be seen by the S.P.C'10)

Claims (2)

[Claims] (1) The reflective surface of the beam splitter is tilted at 45 degrees with respect to the optical axis of the incident light, and the reflective surface of the beam splitter has a structure that can rotate around the optical axis of the incident light. Multi-branch optical device. (2) One of the two cylinders is joined so that the central axis of each cylinder is perpendicular to the side surface of the other cylinder, and the side surface of the cylinder inside the joint is hollow, and the center of the two cylinders is The reflective surface is on the intersection of the axes with the central axis of the two cylinders and 45
A beam splitter holder characterized in that the beam splitter is held at an angle of 100 degrees.