JP2001156371A - Optical branching method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To branch one laser beam into a plurality of parallel beams having equal light intensity under simple constitution, and to easily align the beams. SOLUTION: In the optical branching method, a pair composed of a light reflecting surface 1 and a light branching surface 2 mutually arranged in parallel is inclined and arranged in the projection direction of a laser beam Lo, a transmitting beam L1 at a time when the laser beam Lo is projected to the first spot P1 of the light branching surface 2 on the rear stage side is used as the first beam while a reflecting beam at the first spot P1 is total-reflected by the light reflecting surface 2 and projected to the second spot P2 of the light branching surface 2, and the projection and the reflection are repeated up to the N spot and the beam is branched into N transmitting beams while reflectivity represented by the following formula (1) is used as ones Ri at each spot of the light branching surface 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical splitting method for splitting a laser beam into a plurality of beams.

[0002]

2. Description of the Related Art When one laser beam is split into a plurality of beams, and the plurality of beams are transmitted spatially to be used for optical communication, each beam is made several cm in consideration of fluctuations in the atmosphere in order to stabilize the reception intensity. It is necessary to transmit at a distance above.

In this case, one laser beam is split into a plurality of laser beams which are parallel and have the same light intensity. The splitting method is as follows: (1) One high-power laser beam is split by an optical system. And (2) a method of emitting a laser beam from each laser device using a plurality of laser devices. In the case of (2), a plurality of laser devices are required, the size of the entire system is increased, and the cost is high. In addition, since it is necessary to align the respective beams, adjustment becomes difficult. on the other hand,
In the case of (1), the alignment is easy because the system is simple.

Therefore, when the branching method (1) is adopted, the branching method includes a method using an optical fiber and a method using an optical system such as a beam splitter. When an optical fiber is used, an optical system for collimating each beam at the fiber exit end is required, and alignment adjustment of each beam is required. on the other hand,
When an optical system such as a beam splitter is used, the alignment of all the beams can be made common by collimating and adjusting the alignment of one laser beam before splitting, so that splitting into multiple parallel beams is possible. Relatively easy.

[0005]

However, even if the method (1) described above is used and the beam is split into a plurality of beams using an optical system such as a beam splitter, the optical system components to be used. However, there are still many cases, the configuration is complicated, and it is necessary to set the light intensities to be equal to each other. Therefore, the alignment is difficult and time is required in combination with the complicated configuration.

[0006] The present invention has been proposed in view of the above,
It is an object of the present invention to provide an optical splitting method that can split a single laser beam into a plurality of beams having parallel and equal light intensities under a simple configuration, and that can easily perform the alignment.

[0007]

According to a first aspect of the present invention, there is provided an optical branching method for splitting a laser beam into a plurality of beams, the method comprising the steps of: Are arranged so that the light reflecting surface is on the front side while being inclined with respect to the projection direction of the laser beam, and the transmitted beam when the laser beam is projected on the first point on the light branching surface on the rear side is defined as the first beam. At the same time, the reflected beam at the first point is totally reflected by the light-reflecting surface on the preceding stage and projected to the second point on the light branching surface. And the reflectance Ri at each point from the first point to the N-th point on the light splitting surface is expressed by the following equation (1).

It is characterized in that the light branch surface is provided with a reflectance distribution so that the reflectance is expressed by the following formula.

According to a second aspect of the present invention, in the optical splitting method for splitting a laser beam into a plurality of beams, the light reflecting surface and the light splitting surface parallel to each other are inclined with respect to the projection direction of the laser beam. It is arranged so that the light splitting surface is on the front side, and the reflected beam when the laser beam is projected on the first point on the light splitting surface on the front side is the first beam, and the transmitted beam at the first point is the latter. The light is totally reflected by the light reflecting surface on the side and is projected on the second point of the light branching surface, and the transmitted beam when projected on the second point is used as the second beam, and the reflected beam at the second point is reflected on the light reflecting surface The laser beam is totally reflected and projected to the third point of the light splitting surface, and the projection and reflection from the second point onward are repeatedly performed to the Nth point to split the laser beam into N beams. The reflectance R1 at the first point is 1 = As a reflectance represented by 1 / N, also the reflectance Ri of each point from the second point to the N-th point is the following formula (2)

It is characterized in that the light branch surface has a distribution of the reflectance so that the reflectance is expressed by the following equation.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect of the invention, two sets of the combination of the light reflecting surface and the light branching surface are separated from each other. , And arranged in different directions from each other, splitting the laser beam with these two sets to distribute the beam two-dimensionally,
It is characterized by:

Further, in the invention according to claim 4, in addition to the configuration according to any one of claims 1 to 3, the light reflecting surface and the light branching surface are integrally formed of a bulk optical material. Is formed.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is an explanatory diagram of an optical branching method according to the present invention. Here, a case where one laser beam L0 is branched into four beams will be described. As shown in the drawing, in the light splitting method according to the present invention, a pair of a mirror (light reflecting surface) 1 and a beam splitter (light splitting surface) 2 is formed by a laser beam L.
It is arranged parallel to each other so that it is inclined by an angle α (= π / 2−θ) with respect to the projection direction of 0, and the mirror 1 is at the front stage and the beam splitter 2 is at the rear stage.

This pair of mirror 1 and beam splitter 2
, First, the laser beam L0 is directly projected on the first point P1 of the beam splitter 2 on the subsequent stage. At this time,
The laser beam L0 passes outside the former-stage mirror 1. The laser beam L0 is incident on the first point at an incident angle θ, a part of the laser beam L0 passes through the beam splitter 2 as it is, and becomes a transmitted beam L1, and the rest is reflected at the first point P1 in the direction of the angle θ.

This reflected light is then totally reflected by the mirror 1 and is projected on the second point P2 of the beam splitter 2, and is incident on the second point P2 at an incident angle θ, similar to the case at the first point P1. Meanwhile, a part of the light beam passes through the beam splitter 2 as it is to become a transmitted beam L2, and the rest is reflected at the second point P2 in the direction of the angle θ.

The reflected light is then totally reflected by the mirror 1 and is projected on a third point P3 of the beam splitter 2, and is incident on the third point P3 at an incident angle θ, where the first point P1 and the second point P2 As in the case of the above, a part is transmitted through the beam splitter 2 as it is to become a transmitted beam L3, and the rest is reflected at the third point P3 in the direction of the angle θ. This reflected light is then totally reflected by the mirror 1 and projected on the fourth point P4 of the beam splitter 2, and is incident on the fourth point P4 at an incident angle θ, and all of the light is transmitted at the fourth point P4. Thus, a transmission beam L4 is obtained.

Here, assuming that the distance between the mirror 1 and the beam splitter 2 is d, the distance between the transmitted beams L1 to L4 is 2 dsin θ, and the distance between the transmitted beams L1 to L4 is to stabilize the reception intensity. Considering the fluctuation of the atmosphere, the distance should be longer than the coherence length of the atmosphere. Also,
Considering the mutual interference of the laser beams, the optical path difference delay 2dcos θ / c (c is the speed of light) of each beam is set longer than the time coherence length of the laser.

As described above, the laser beam L0 is split into four parallel transmitted beams L1 to L4, and in this embodiment, each part of the beam splitter 2 from the first point P1 to the fourth point P4. The reflectance Ri at a point is given by the following equation (3).

(Equation 3) The beam splitter 2 has a distribution of the reflectance so that the reflectance is represented by the following expression.

That is, from the above equation (3), the reflectance R1 at the first point P1 is 3/4, the reflectance R2 at the second point P2 is 2/3, and the reflectance R3 at the third point P3 is R3. Is 1/2,
The reflectance R4 at the fourth point P4 is zero. Here, when the light intensity of the laser beam L0 is I0, the transmitted beam L
The light intensities I1 to I4 of the transmitted beams L1 to L4 are given by the following equation (4).
It becomes 0 and becomes equal intensity.

(Equation 4)

In the above description, the laser beam L0
Has been described, the beam splitter 2 can be provided with a distribution of the reflectance in the same manner as described above even when the beam splitter is arbitrarily branched into N beams. The light intensities of the beams L1 to LN are all 1 /
N · I0 and equal strength.

As described above, in the embodiment according to the present invention, one set of the mirror 1 and the beam splitter 2 arranged in parallel with each other is arranged obliquely with respect to the projection direction of the laser beam L0. Is transmitted to the first point P1 of the subsequent beam splitter 2 as a first beam, and the reflected beam at the first point P1 is totally reflected by the front mirror 1 to form a beam splitter 2 At the second point P2, and the projection and reflection are repeatedly performed up to the N-th point to split the laser beam into N transmission beams, and to give the beam splitter 2 a distribution of the reflectance, and Was set to be the reflectance represented by the above (1). For this reason,
One laser beam L0 can be split into a plurality of beams of parallel and equal light intensity under a simple configuration, and the alignment can be easily performed. Further, the laser beam branching device can be manufactured at low cost.

Next, a second embodiment of the optical branching method according to the present invention will be described with reference to FIG.

FIG. 2 is an explanatory diagram when the incident direction of the laser beam is different from that of FIG. In FIG. 1, the mirror 1 is arranged at the front stage and the beam splitter 2 is arranged at the rear stage with respect to the projection direction of the laser beam L0. However, in FIG. 2, the beam splitter 102 is arranged with respect to the projection direction of the laser beam L0. At the front stage, the mirror 101 is arranged so as to be at the rear stage.

Due to this difference, in the second embodiment, the reflected beam when the laser beam L0 is projected on the first point P1 of the beam splitter 102 is defined as a first beam L101 and the first point P1 Is transmitted to the second point P2 of the beam splitter 102, and the transmitted beam when projected onto the second point P2 is defined as a second beam L102 and the second point The reflected beam at P2 is mirror 101
At the third point P3 of the beam splitter 102
The laser beam L0 is branched into four beams by repeatedly performing the projection and reflection from the second point P2 to the fourth point P4.

Further, with respect to the beam splitter 102, the reflectance R1 at the first point P1 is R1 = 1 / N = 1.
/ 4, and the second point P
The reflectance Ri at each point from the 2 to the N-th point is given by the following equation (5).

(Equation 5) The beam splitter 10 is set to have a reflectance represented by
2 has a reflectance distribution.

Also in the case of the second embodiment, the number of laser beams L0 is not limited to four, and the beam splitter 102 is provided with a distribution of the reflectance by the same method as described above, so that the light It is possible to branch into arbitrary N lines having the same intensity.

In the description of FIG. 2, the mirror 101
The beam splitter 102 and the beam splitter 102 are arranged in parallel. Instead of the mirror 101 and the beam splitter 102, a bulk optical material 103 made of glass or the like may be used as shown in FIG. When this bulk optical material 103 is used, both surfaces 103a and 103b of the bulk optical material 103 are processed in parallel, and one surface 103a is used as a light reflecting surface and the other surface 103b is used as a light branching surface. Mirror 101 and beam splitter 10
By using the integral bulk optical material 103, the number of parts can be reduced by half, and parallel alignment can be obtained extremely easily, as compared with the case where 2 is used.

Next, a third embodiment of the optical branching method according to the present invention will be described with reference to FIG.

Although the method for one-dimensionally splitting the laser beam L0 has been described with reference to FIGS. 1 and 2, a method for two-dimensionally splitting the laser beam L0 will be described here.

FIG. 4 is an explanatory view showing a case where a laser beam is two-dimensionally branched by the optical branching method of the present invention. In order to split the laser beam L0 two-dimensionally, as shown in the figure, first, a set C1 composed of a mirror 11 and a beam splitter 12 and a pair C2 composed of a mirror 21 and a beam splitter 22 are formed by a laser. They are arranged apart from each other with respect to the projection direction of the beam L0. It should be noted that which pair C1, C
Also in 2, the mirrors 11 and 21 are arranged at the front stage, the beam splitters 12 and 22 are arranged at the rear stage, and they are arranged in parallel with each other. One set C1 is set by rotating it about a vertical axis M1 provided on a plane orthogonal to the projection direction of the laser beam L0 by a predetermined angle β in plan view (in the figure, as viewed in the direction of arrow X). . The other set C2 has the laser beam L0 in a plane parallel to the projection direction of the laser beam L0.
The setting is made by rotating by a predetermined angle γ in a side view (viewed in the direction of the arrow Y in the figure) about an axis M2 provided so as to be orthogonal to the projection direction of 0.

Under such a configuration, first, the laser beam L0 passes through the outside of the mirror 11 of one set C1 and is directly projected on the beam splitter 12, and the projection and reflection are repeated in the same manner as in FIG. Thereby, four transmitted beams L11 to L14 are obtained.

Subsequently, the four transmitted beams L11 to L11
14 is passed through the outside of the mirror 21 of the other set C2 and is directly projected on the beam splitter 22, and the projection and reflection are repeated in the same manner as in FIG. 1 described above, whereby, for example, four beams are transmitted from one transmitted beam L11. Transmitted beams L111 to L
114 were obtained, and thus 4 rows × 4 columns, a total of 16
Two transmitted beams are obtained in two dimensions. Since the reflectance at each point where the laser beam is projected on the beam splitters 21 and 22 is set to the reflectance determined by the above-described equation (3), as in the case of FIG.
The six transmitted beams L111 and the like also have light intensity (1/16 · I0) parallel and equal to each other.

Therefore, even when one laser beam L0 is branched two-dimensionally, it can be branched into a plurality of beams having parallel and equal light intensities with a simple structure, and its alignment is also smaller than that of the conventional method. It can be performed much easier and in a shorter time. Further, the laser beam branching device can be manufactured at low cost.

In the above description, the laser beam L0
Has been described as branching into 4 × 4 = 16 lines,
Similarly, it is possible to branch to any (N × N) lines,
In this case, the light intensities of the (N × N) transmitted beams are all {1 / (N × N)} · I0.

The plurality of laser beams obtained in this manner are used, for example, in the field of spatial optical communication where a laser beam is radiated spatially, in the field of optical communication where optical signals need to be equally distributed, and In the field of processing technology that requires precise positioning, and in the field of measurement technology that recognizes the shape of objects using spatial markers,
It can be used effectively.

[0035]

Since the present invention has the above-described configuration,
The following effects can be obtained.

According to the first and second aspects of the present invention, a laser beam is formed by using a pair of a light reflecting surface arranged in parallel with each other and a light branching surface having a predetermined reflectance distribution. Since the laser beam is split into a plurality of beams, one laser beam can be split into a plurality of beams of parallel and equal light intensity under a simple configuration, and the alignment can be easily performed. Further, the laser beam branching device can be manufactured at low cost.

According to the third aspect of the present invention, the laser beam is split by using two sets of a light reflecting surface arranged in parallel with each other and a light splitting surface having a predetermined reflectance distribution. Therefore, under the simple structure, it is possible to split into multiple beams of parallel and equal light intensity, and the two beams can be split two-dimensionally, so that the alignment is much easier than the conventional method. It can be performed in a short time. Further, a laser beam branching device that branches two-dimensionally can be manufactured at low cost.

According to the fourth aspect of the present invention, since a bulk optical material is used instead of the light reflecting surface and the light branching surface, the number of parts can be reduced by half, and the parallel alignment can be performed. It can be obtained very easily.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an optical branching method according to the present invention.

FIG. 2 is an explanatory diagram of a second embodiment of the present invention.

FIG. 3 is an explanatory diagram when a bulk optical material is used.

FIG. 4 is an explanatory diagram of a case where a laser beam is two-dimensionally branched according to a third embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 mirror (light reflecting surface) 2 beam splitter (light splitting surface) 11 mirror (light reflecting surface) 12 beam splitter (light splitting surface) 21 mirror 22 beam splitter 101 mirror 102 beam splitter 103 bulk optical material 103a light reflecting surface 103b light Branch surface L0 Laser beam L1 to L4 Transmitted beam L11 to L14 Transmitted beam L111 to L114 Transmitted beam L101 Reflected beam (first beam) L102 to L104 Transmitted beam (second to fourth beam)

Claims (4)

[Claims] 1. A light splitting method for splitting a laser beam into a plurality of beams, wherein a light reflecting surface and a light splitting surface parallel to each other are inclined with respect to a projection direction of the laser beam, and the light reflecting surface is located on a front stage side. And the transmitted beam when the laser beam is projected on the first point on the light splitting surface on the subsequent stage is defined as the first beam, and the reflected beam at the first point is totally reflected on the light reflecting surface on the preceding stage. To the second point of the light splitting surface, and the projection and reflection are repeated to the Nth point to split the laser beam into N transmission beams, and from the first point to the Nth point of the light splitting surface. The reflectance Ri at each point is expressed by the following equation (1). An optical branching method characterized in that the optical branching surface has a distribution of the reflectance so that the reflectance is represented by the following formula. 2. A light splitting method for splitting a laser beam into a plurality of beams, wherein a light reflecting surface and a light splitting surface which are parallel to each other are inclined with respect to a projection direction of the laser beam, and the light splitting surface is located on a front side. And the reflected beam when the laser beam is projected to the first point of the light splitting surface on the front side is defined as the first beam, and the transmitted beam at the first point is totally reflected by the light reflecting surface on the subsequent side. To the second point of the light branching surface, and the transmitted beam when projected at the second point is used as the second beam, and the reflected beam at the second point is totally reflected by the light reflecting surface to form a second beam. The laser beam is projected to the third point, and the projection and reflection from the second point onward are repeated to the Nth point to split the laser beam into N beams, and the first beam on the light splitting surface.
The reflectance R1 at the point is set to be the reflectance represented by R1 = 1 / N, and the reflectance Ri at each point from the second point to the Nth point is expressed by the following equation (2). ] An optical branching method characterized in that the optical branching surface has a distribution of the reflectance so as to have a reflectance represented by: 3. A combination of two sets of the light reflecting surface and the light splitting surface, which are spaced apart from each other and arranged so as to be inclined in different directions. The two sets split a laser beam and two-dimensionally split the beam. The optical branching method according to claim 1, wherein the light is distributed. 4. The light splitting method according to claim 1, wherein the light reflecting surface and the light splitting surface are integrally formed of a bulk optical material.