Optical coupling device

Abstract

This optical coupling device couples a plurality of beams to a single fiber. A plurality of light sources is arranged at predetermined intervals and emits the plurality of beams. A plurality of collimating lens is arranged to face the plurality of light sources and collimates the plurality of beams emitted from the plurality of light sources. A reduction optical system reduces the beam diameter of the plurality of beams collimated by the plurality of collimating lens. A focusing lens focuses the plurality of beams reduced by the reduction optical system on a fiber. A first distance between the light source and the collimating lens arranged so as to correspond to a beam passing through the center of the reduction optical system is different from a second distance between the light source and the collimating lens arranged so as to correspond to a beam passing through the end portion of the reduction optical system.

Claims

1. An optical coupling device for coupling a plurality of beams to a single fiber, comprising: a plurality of light sources configured to emit the plurality of beams, the plurality of light sources being arranged at predetermined intervals; a plurality of collimating lens configured to collimate the plurality of beams emitted from the plurality of light sources, the plurality of collimating lens being arranged to face the plurality of light sources; a reduction optical system configured to reduce a beam diameter of the plurality of beams collimated by the plurality of collimating lens; a focusing lens configured to focus the plurality of beams reduced by the reduction optical system on the fiber; and a collimator in which the light source and the collimating lens arranged so as to correspond to the beam passing through an end portion of the reduction optical system are integrated, wherein the collimator is inclined at a predetermined angle so that the beam is obliquely incident on the reduction optical system.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram showing the entire configuration of an optical coupling device according to Example 1 of the present invention.

(2) FIG. 2 shows focusing properties of the lens used in the optical coupling device according to Example 1 of the present invention.

(3) FIG. 3 is a diagram showing aberrations before and after correcting the aberration at a position where the beam from the laser diode 1b of the optical coupling device according to Example 1 of the present invention is condensed by the focusing lens.

(4) FIG. 4 is a diagram showing the entire configuration of an optical coupling device according to Example 2 of the present invention.

(5) FIG. 5 is a diagram showing the entire configuration of an optical coupling device according to Example 3 of the present invention.

(6) FIG. 6 is a diagram showing the entire configuration of an optical coupling device according to Example 4 of the present invention.

(7) FIG. 7 is a diagram showing the entire configuration of an optical coupling device according to Example 5 of the present invention.

(8) FIG. 8 is a diagram showing the entire configuration of an optical coupling device according to Example 6 of the present invention.

(9) FIG. 9 is a diagram showing the entire configuration of an optical coupling device according to Example 7 of the present invention.

(10) FIG. 10 is a diagram showing the entire configuration of an optical coupling device according to Example 8 of the present invention.

EMBODIMENTS FOR CARRYING OUT THE INVENTION

Example 1

(11) Hereinafter, an optical coupling device according to an embodiment of the present invention will be described in detail with reference to the attached drawings. FIG. 1 is a diagram showing the entire configuration of the optical coupling device according to Example 1 of the present invention. The optical coupling device is configured to couple a plurality of beams to a single fiber 5 and is provided with a plurality of laser diodes 1a to 1c, a plurality of collimating lenses 2a to 2c, a reduction optical system 3, a focusing lens 4, and a fiber 5.

(12) The plurality of laser diodes 1a to 1c corresponds to the plurality of light sources of the present invention and is arranged at predetermined intervals. Each laser diode emits a laser beam. In this Example, three laser diodes are arranged, but not limited thereto, four or more laser diodes may be arranged at predetermined intervals.

(13) As the light source, a light-emitting diode, a surface-emitting laser (VCSEL), or an electroluminescent (EL) may be used in place of each of the plurality of laser diodes 1a to 1c.

(14) The plurality of collimating lenses 2a to 2c is arranged to face the plurality of laser diodes 1a to 1c, respectively, to collimate the plurality of beams emitted from the plurality of laser diodes 1a to 1c.

(15) The reduction optical system 3 is composed of a telescope having a convex lens 3a and a concave lens 3b and is configured to reduce the beam diameter and the beam spacing of the plurality of beams from the plurality of collimating lenses 2a to 2c to guide the beams to the focusing lens 4.

(16) The convex lens 3a and the concave lens 3b each consists of a spherical lens and has a spherical aberration. The focusing lens 4 focuses the plurality of beams reduced by the reduction optical system 3 on the fiber 5.

(17) A first distance Z1 between the laser diode 1a and the collimating lens 2a arranged so as to correspond to a beam passing through a center of the reduction optical system 3 is configured to be different from a second distance Z2 between the laser diode 1b (1c) and the collimating lens 2b (2c) arranged so as to correspond to a beam passing through an end portion of the convex lens 3a of the reduction optical system 3.

(18) When the spherical aberration of the reduction optical system 3 equipped with the convex lens 3a and the concave lens 3b is positive, the second distance Z2 is made smaller than the first distance Z1.

(19) Next, the operation of the optical coupling device of Example 1 configured as described above will be described. FIG. 2 shows the focusing property of the lens used for the optical coupling device. The beam incident on the convex lens becomes longer in the focal length to the focal point f4 as it is closer to the center O of the lens, and the shorter the focal lengths to the focal points f1 and f2 as it approaches the end portions P1 and P2 of the lens.

(20) Therefore, a spherical aberration is generated. When the light incident on the periphery of the lens is focused on a side closer to the lens than the focal point by the light incident on the vicinity of the center of the lens, it is referred to as a positive spherical aberration. In FIG. 2, a positive spherical aberration is generated.

(21) In Example 1 shown in FIG. 1, when the distance between the laser diode 1b (1c) and the collimating lens 2b (2c) arranged so as to correspond to the end portion of the convex lens 3a is Z1, the beams BM1 emitted from the collimating lenses 2b and 2c are parallel light. Here, it is considered that a positive spherical aberration is generated when the beam is incident on the outer side of the convex lens 3a.

(22) On the other hand, in Example 1, the distance Z2 between the laser diode 1b (1c) and the collimating lens 2b (2c) arranged so as to correspond to the end portion of the convex lens 3a is made smaller than the first distance Z1. The beam BM2 diverges (expands outward by the angle φ with respect to the collimated light beam BM1) and is incident on the end portion side (outer side) of the convex lens 3a.

(23) Therefore, the diverging beam BM2 is condensed by the convex lens 3a, and the focal position moves further than the focal position when the beam BM1 is condensed by the convex lens 3a. Therefore, it is possible to suppress the positive spherical aberration.

(24) FIG. 3 shows aberrations before and after correcting the aberration at the position where the beam from the laser diode 1b is condensed by the focusing lens. The vertical axis indicates the aberration amount, and the horizontal axis indicates the image height after passing through the collimating lens. FIG. 3 shows the comparison between the aberration amount before spherical aberration correction when the distance Z2 is equal to the distance Z1 and the aberration amount after spherical aberration correction when the distance Z2 is different from the distance Z1.

(25) Before the aberration correction, when the image height increases (e.g., the image height 1), the aberration amount increases.

(26) On the other hand, after the aberration correction of Example 1, when the image height becomes large, the aberration amount decreases as compared with that before the correction. For example, as shown in FIG. 1, when focusing on the fiber 5 of the core of 100 μm, when the aberration amount shown in FIG. 3 exceeds 100 μm, the beam diameter also exceeds 100 μm. Therefore, the power is lost at the fiber 5.

(27) On the other hand, after the aberration correction of Example 1, the aberration amount is 100 μm or less at any image height, and therefore the loss at the fiber 5 can be reduced as compared with the case before the aberration correction.

(28) According to the optical coupling device of Example 1 as described above, as compared with the first distance Z1 between the laser diode 1a and the collimating lens 2a arranged so as to correspond to the beam passing through the center of the reduction optical system 3, the second distance Z2 between the laser diode 1b (1c) and the collimating lens 2b (2c) arranged so as to correspond to the beam passing through the end portion of the reduction optical system 3 is configured to be smaller. Therefore, it is possible to suppress the spherical aberration of the light from the laser diodes 1a to 1c to improve the fiber coupling efficiency.

Example 2

(29) FIG. 4 is a diagram showing the entire configuration of an optical coupling device according to Example 2 of the present invention. The optical coupling device according to Example 2 includes a reduction optical system 3 having a convex lens 3a and a concave lens 3b. When the beams are incident on a position away from the central axis of the focusing lens 4, the spherical aberration is considered to be positive. The optical coupling device of Example 2 is provided with a collimator 10b (10c) in which a laser diode 1b (1c) and a collimating lens 2b (2c) arranged so as to correspond to the beam passing through the end portion of the reduction optical system 3 are integrated.

(30) The collimator 10b (10c) is arranged so as to be inclined at a predetermined angle φ so that the beam is obliquely incident on the reduction optical system 3. More specifically, the collimator 10b (10c) is arranged such that the beam BM2 emitted from the collimator 10b (10c) is inclined outward by a predetermined angle φ (φ>0) with respect to the beam BM1 consisting of parallel light, and causes the beam BM2 to be incident on the convex lens 3a obliquely.

(31) The rest of the configuration shown in FIG. 4 is the same as the configuration of the optical coupling device according to Example 1 shown in FIG. 1, and therefore the descriptions of the same portions will be omitted.

(32) According to the optical coupling device of Example 2 configured as described above, since the collimator 10b (10c) is arranged such that the beam BM2 is inclined outward by a predetermined angle φ with respect to the beam BM1, the beam BM2 is diverged with respect to the beam BM1, and the beam BM2 is obliquely incident on the convex lens 3a. Therefore, it is possible to suppress the spherical aberration of the light from the laser diodes 1a to 1c to improve the fiber coupling efficiency.

Example 3

(33) FIG. 5 is a diagram showing the entire configuration of an optical coupling device according to Example 3 of the present invention. The optical coupling device according to Example 3 includes a reduction optical system 3 having a convex lens 3a and a concave lens 3b. When the beam is incident on a position away from the central axis of the focusing lens 4, the spherical aberration is considered to be positive. In the optical coupling device according to Example 3 shown in FIG. 5, the distance Z2 between the laser diode 1b (1c) and the collimating lens 2b (2c) arranged so as to correspond to the end portion of the convex lens 3a is smaller than the first distance Z1.

(34) The collimator 10d (10e) is arranged so as to be inclined by a predetermined angle φ to diverge the beam BM2 with respect to the beam BM1, and causes the beam BM2 to be incident on the convex lens 3a obliquely.

(35) According to the optical coupling device of Example 3 configured as described above, the distance Z2 between the laser diode 1b (1c) and the collimating lens 2b (2c) is made smaller than the first distance Z1, and the collimator 10d (10e) is arranged so as to be inclined by a predetermined angle φ to diverge the beam BM2 with respect to the beam BM1. Therefore, the combined effect in which the effect of the optical coupling device of Example 1 and the effect of the optical coupling device of Example 2 are combined can be obtained.

Example 4

(36) FIG. 6 is a diagram showing the entire configuration of an optical coupling device according to Example 4 of the present invention. The optical coupling device according to Example 4 includes a reduction optical system 3 having a convex lens 3a and a concave lens 3b. When the beam is incident on a position away from the central axis of the focusing lens 4, the spherical aberration is considered to be positive. In the optical coupling device according to Example 4, the laser diode 1a and the collimating lens 2a arranged so as to correspond to the beam passing through the center of the reduction optical system 3 are arranged on the optical axis.

(37) The laser diode 1b and the collimating lens 2b arranged so as to correspond to the beam passing through the end portion of the reduction optical system 3 are arranged such that the center O of the collimating lens 2b is shifted in the positive X-direction (X>0) with respect to the center of the laser diode 1b.

(38) The laser diode 1c and the collimating lens 2c arranged so as to correspond to the beam passing through the end portion of the reduction optical system 3 are arranged such that the center O of the collimating lens 2c is shifted in the negative X-direction (X<0) with respect to the center of the laser diode 1c.

(39) According to the optical coupling device according to Example 4, since the center O of the collimating lens 2b is shifted in the positive X-direction (X>0) with respect to the center of the laser diode 1b, the beam BM2 diverged outward than the beam BM1 is incident on the convex lens 3a.

(40) Further, since the center O of collimating lens 2c is shifted in the negative X-direction (X<0) with respect to the center of the laser diode 1c, the beam BM2 diverged outward than the beam BM1 is incident on the convex lens 3a. Therefore, the same effect as the effect of the optical coupling device of Example 1 can be obtained.

Example 5

(41) FIG. 7 is a diagram showing the entire configuration of an optical coupling device according to Example 5 of the present invention. The optical coupling device according to Example 5 includes a reduction optical system 3. When the beam is incident on a position away from the central axis of the focusing lens 4, the spherical aberration is considered to be positive, and therefore the second distance Z2 is made to be larger than the first distance Z1.

(42) The rest of the configuration shown in FIG. 7 has the same configuration as that of the optical coupling device according to Example 1, and therefore, the same reference numerals are assigned to the same portions, and the descriptions thereof will be omitted.

(43) According to the optical coupling device of Example 5, since the spherical aberration due to the reduction optical system 3 is negative and the second distance Z2 is made larger than the first distance Z1, the beam BM3 passed through the collimating lens 2b (2c) from the laser diode 1b (1c) is condensed inward with respect to the parallel beam BM1 by the angle φ (φ0) and is incident on the center side of the convex lens 3a. Therefore, the same effect as the effect of the optical coupling device of Example 1 can be obtained.

Example 6

(44) FIG. 8 is a diagram showing the entire configuration of an optical coupling device according to Example 6 of the present invention. In the optical coupling device according to Example 6, the spherical aberration due to the reduction optical system 3 is negative.

(45) The collimator 10d (10e) is arranged such that the beam BM3 emitted from the collimator 10d (10e) is inclined inward by a predetermined angle φ (φ<0) with respect to the beam BM1 composed of collimated light, and causes the beam BM3 to be incident on the convex lens 3a obliquely.

(46) The rest of the configuration shown in FIG. 8 has the same configuration as that of the optical coupling device according to Example 2, and therefore the same reference numerals are assigned to the same portions, and the descriptions thereof will be omitted.

(47) According to the optical coupling device according to Example 6, the same effect as the effect of optical coupling device of Example 2 can be obtained.

Example 7

(48) FIG. 9 is a diagram showing the entire configuration of an optical coupling device according to Example 7 of the present invention. In the optical coupling device according to Example 7, the spherical aberration caused by the reduction optical system 3 is negative, and the second distance Z2 is larger than the first distance Z1.

(49) The collimator 10d (10e) is arranged such that the beam BM3 emitted from the collimator 10d (10e) is inclined inward by a predetermined angle φ (φ<0) with respect to the beam BM1 composed of collimated light, and causes the beam BM3 to be incident on the convex lens 3a obliquely.

(50) The rest of the configuration shown in FIG. 9 has the same configuration as that of the optical coupling device according to Example 3, and therefore, the same reference numerals are assigned to the same portions, and the descriptions thereof will be omitted.

(51) According to the optical coupling device according to Example 7, the effect in which the effect of the optical coupling device of Example 1 and the effect of the optical coupling device of Example 2 are combined can be obtained.

Example 8

(52) FIG. 10 is a diagram showing the entire configuration of an optical coupling device according to Example 8 of the present invention. In the optical coupling device according to Example 8, the spherical aberration due to the reduction optical system 3 is negative.

(53) In the optical coupling device according to Example 8, the laser diode 1a and the collimating lens 2a arranged so as to correspond to the beam passing through the center of the reduction optical system 3 are arranged on the optical axis.

(54) The laser diode 1b and the collimating lens 2b arranged so as to correspond to the beam passing through the end portion of the reduction optical system 3 are arranged such that the center O of the collimating lens 2b is shifted in the negative X-direction (X<0) with respect to the center of the laser diode 1b.

(55) The laser diode 1c and the collimating lens 2c arranged so as to correspond to the beam passed through the end portion of the reduction optical system 3 are arranged such that the center O of the collimating lens 2c is shifted in the positive X-direction (X>0) with respect to the center of the laser diode 1c.

(56) According to the optical coupling device according to Example 8, since the center O of the collimating lens 2b is displaced in the negative X-direction (X<0) with respect to the center of the laser diode 1b, the beam BM3 focused inward of the beam BM1 is incident on the convex lens 3a.

(57) Further, since the center O of the collimating lens 2c is shifted from the center of the laser diode 1c in the positive X-direction (X>0), the beam BM3 focused inward of the beam BM1 is incident on the convex lens 3a. Therefore, the same effect as the effect of the optical coupling device of Example 1 can be obtained.

(58) Note that the present invention is not limited to the optical coupling devices of Example 1 to Example 8 described above. Any two or more Examples of the optical coupling devices of Example 1 to Example 8 may be combined.

INDUSTRIAL APPLICABILITY

(59) The present invention is applicable to laser machining, exposure, lighting, imaging, medicine, and the like.