JP2014022700A - Optical module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical module which suppresses optical coupling between a reflecting return light and a light emitting element, is convenient, and is excellent in optical performance.SOLUTION: An optical module 10 comprises a light emitting element 11 for emitting light and a window lens 2 which light transmits, and emits light that has transmitted the window lens 2 outside. The window lens 2 is provided on its surface with a first lens surface 2a and on its back surface with a second lens surface 2b. In the optical module 10, optical axes of the light emitting element 11 and of the window lens 2 coincide, the first lens surface 2a is provided facing the light emitting element 11, and one of the first lens surface 2a and the second lens surface 2b is a projection surface, and the other is a recessed surface.

Description

  The present invention relates to an optical module that suppresses optical coupling between a light emitting element that emits light and reflected return light.

  In the optical communication field, an optical module is used that has a housing that houses a light emitting element and includes a light-transmitting window through which the emitted light passes. The translucent window is made of plate-like glass, and the housing is filled with an inert gas such as helium and hermetically sealed in order to prevent oxidation of the emission part of the light emitting element.

  By the way, the emitted light emitted from the light emitting element passes through the light transmitting window and is emitted to the outside of the housing. At this time, part of the emitted light is reflected by the light transmitting window and returns to the light emitting element, and noise caused by the reflected return light is a problem.

  An optical module (semiconductor laser device) for solving this problem is disclosed in Patent Document 1. FIG. 12 is a schematic cross-sectional view of an optical module disclosed in Patent Document 1. As shown in FIG. 12, in the optical module 500, an opening 511b through which laser light is transmitted is formed on an upper surface 511a of a housing 511 (cap) that houses a semiconductor laser 513 that is a light emitting element. Then, a plate-like plate glass 502 (cover glass) is fixed by a low melting point glass 508 so as to block the opening 511 b on the inner side surface 511 c of the housing 511.

  The plate glass 502 is provided non-orthogonally with respect to the optical axis 515 of the semiconductor laser 513 so that the laser light reflected by the plate glass 502 does not return to the semiconductor laser 513.

JP 2011-216583 A

  FIG. 13 is an explanatory diagram of the influence of the plate-like glass disclosed in Patent Document 1 on the optical path of laser light. As shown in FIG. 13, in the optical module 500, the diffused light 514a emitted from the semiconductor laser 513 passes through the plate glass 502 and is emitted outside the housing 511 (not shown in FIG. 13). At this time, the light beam 514b in the vicinity of the optical axis 515 of the diffused light 514a travels almost parallel to the optical axis 515 on the optical axis 515 until it is emitted from the semiconductor laser 513 and enters the plate glass 502.

  However, the plate glass 502 is provided so as to be non-orthogonal with respect to the optical axis 515 of the semiconductor laser 513, that is, the normal line 502a of the plate glass 502 and the optical axis of the semiconductor laser 513 are inclined with respect to each other. Therefore, when the diffused light 514a is transmitted through the plate glass 502, the light beam 514b is on the optical path 515a shifted from the optical axis 515 depending on the inclination angle 502b between the optical axis 515 and the normal line 502a and the thickness of the plate glass 502. It travels almost parallel to the optical axis 515.

  When the optical module 500 is used for optical communication, the diffused light 514a transmitted through the plate glass 502 is converted into parallel light using a collimator lens (not shown), and then used using a condensing lens (not shown). It is condensed on the end face of an optical fiber (not shown). At this time, since the light beam 514b travels on the optical path 515a shifted from the optical axis 515, it is necessary to align the optical axis of the collimating lens with the shifted optical path 515a.

  Thus, it is necessary to shift the optical axis of the collimating lens from the optical axis 515 of the semiconductor laser 513 so that the optical axis of the collimating lens is aligned with the optical path 515a. Therefore, the optical module 500 disclosed in Patent Document 1 has a problem that assembly is complicated.

  Further, the diffused light 514a emitted from the semiconductor laser 513 is coupled to a light receiving unit such as an optical fiber using a collimator lens. At that time, the collimating lens and the optical fiber are installed with their positions shifted so that the optical axes of the collimating lens and the optical fiber coincide with the optical path 515a shifted from the optical axis 515. For this reason, there is a problem in that optical performance deteriorates because coupling loss occurs due to shifting of the installation positions of the collimating lens and the optical fiber.

  The object of the present invention has been made in view of such problems, and provides an optical module that suppresses optical coupling between reflected return light and a light-emitting element, is easy to assemble, and has excellent optical performance. That is.

  A light emitting element that emits light; and a window lens that transmits the light; and an optical module that emits the light transmitted through the window lens to the outside. A first lens surface and a second lens surface on the back surface thereof, wherein the light axes of the light emitting element and the window lens are provided so as to coincide with each other, and the first lens surface is provided on the light emitting element. One of the first lens surface and the second lens surface is a convex surface, and the other is a concave surface.

  In the optical module of the present invention, the light emitted from the light emitting element passes through the first lens surface and the second lens surface. At that time, the reflected return light generated by the reflection at the window lens is reflected light from the first lens surface and the second lens surface. In the present invention, one of the first lens surface and the second lens surface is a convex surface, and the other is a concave surface. Therefore, except for the vicinity of the optical axis, the optical path of the reflected return light is different from the optical path of the light emitted from the light emitting element, and therefore the reflected return light is not condensed on the light emitting element.

  Therefore, according to the present invention, the optical coupling between the reflected return light and the light emitting element is suppressed.

  In the optical module of the present invention, the window lens has a concave and convex lens surface. For this reason, even if the optical axes of the light emitting element and the window lens are aligned, the optical coupling between the reflected return light and the light emitting element is suppressed. Therefore, the light passing through the window lens does not change its optical axis before and after passing through the window lens, and travels on an optical path that substantially matches the optical axis of the light emitting element.

  Therefore, the optical module of the present invention does not require optical axis adjustment by shifting the optical axis, and is easy to assemble. Further, since there is no coupling loss caused by shifting the optical axis, the optical performance is excellent.

  Therefore, according to the present invention, it is possible to provide an optical module that suppresses the optical coupling between the reflected return light and the light emitting element, is easy to assemble, and has excellent optical performance.

  A collimating lens for collimating the light; the collimating lens is provided between the light emitting element and the window lens; and the optical axes of the collimating lens and the window lens are provided in parallel. It is preferable that the first lens surface is a convex surface and the second lens surface is a concave surface.

  The optical axes of the light emitting element and the window lens are provided so as to coincide with each other, and the optical axes of the collimating lens and the window lens are provided in parallel. Therefore, the diffused light emitted from the light emitting element becomes parallel light by the collimator lens and enters the window lens. The reflected return light reflected by the window lens is parallel light and is condensed on the light emitting element only when returning to the collimating lens.

  On the other hand, in the window lens, the first lens surface and the second lens surface have the convex surfaces facing the incident light, so that the reflected return light reflected by the window lens is diffused light. Therefore, the reflected return light reflected by the window lens is not condensed on the light emitting element.

  Therefore, according to the present invention, the optical coupling between the reflected return light and the light emitting element is suppressed.

  The light emitting element and the window lens are provided with the same optical axis, and the collimating lens and the window lens are provided with the optical axes in parallel. Therefore, the diffused light emitted from the light emitting element becomes parallel light by the collimator lens and enters the window lens. The parallel light incident on the window lens travels along an optical path that matches the optical axis of the light emitting element without changing its optical axis before and after passing through the window lens.

  Therefore, when the optical module of the present invention is used for optical communication, the optical axis of the light emitting element and the optical axis of the condenser lens for condensing the light emitted from the optical module on the end face of the optical fiber are matched. The optical axis can be adjusted as it is. Therefore, the optical module of the present invention does not require optical axis adjustment by shifting the optical axis, and is easy to assemble. Since an error caused by this shifting does not occur, the optical performance is excellent.

  The collimating lens which makes the 1st lens surface concave, the 2nd lens surface convex, and makes the emitted light of the light emitting element parallel light is provided between the light emitting element and the window lens. In addition, the light axes of the light emitting element, the collimating lens, and the window lens are provided so that the reflected light reflected by the first lens surface is focused between the collimating lens and the window lens. It is preferable that the focal point is at a position closer to the first lens surface side than the midpoint of the distance between the surfaces of the collimating lens facing the window lens and the first lens surface.

  In such an embodiment, a part of the reflected return light can be provided so as to pass outside the collimating lens. At this time, a part of the reflected return light does not return to the light emitting element, so that the optical coupling between the reflected return light and the light emitting element can be further suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, while suppressing the optical coupling | bonding of reflected return light and a light emitting element, it is possible to provide the optical module which is easy to assemble and is excellent in optical performance.

1 is a schematic plan view of a window lens with a lens barrel in a first embodiment. FIG. 2 is a schematic cross-sectional view taken along the line AA shown in FIG. It is an optical module in a 1st embodiment. It is explanatory drawing of the reflected return light in 1st Embodiment. It is an example which used the optical module in 1st Embodiment for optical communication. It is explanatory drawing of the manufacturing method of the window lens with a lens-barrel in 1st Embodiment. It is a modification of the optical module in 1st Embodiment. It is an example which used the optical module of the modification for optical communications. It is an optical module in a 2nd embodiment. It is explanatory drawing of the reflected return light in 2nd Embodiment. It is explanatory drawing of the reflected return light in the 1st deformation | transformation in 2nd Embodiment. 1 is a schematic cross-sectional view of an optical module disclosed in Patent Document 1. It is explanatory drawing of the influence which the plate-shaped glass disclosed by patent document 1 has on the optical path of a laser beam.

<First Embodiment>
This embodiment will be described in detail with reference to the drawings. FIG. 1 is a schematic plan view of a window lens with a lens barrel in the first embodiment. FIG. 2 is a schematic sectional view taken along the line AA shown in FIG. FIG. 3 shows an optical module according to the first embodiment. Each drawing is illustrated with dimensions appropriately changed for easy viewing.

  As shown in FIGS. 1 and 2, the window lens 1 with a lens barrel of the present embodiment includes a cylindrical lens barrel 3 and a window lens 2 that is a circle in plan view. The lens barrel 3 includes an opening 3 a through which light passes, and the opening 3 a is covered with the window lens 2. The lens barrel 3 is manufactured by cutting stainless steel or the like, for example. The window lens 2 is made of transparent glass.

  The window lens 2 includes a first lens surface 2a on the surface of the window lens 2, that is, as shown in FIG. 2, in the upper direction (Z2 direction) in the figure. The window lens 2 includes a second lens surface 2b on the back surface of the window lens 2, that is, in the lower direction (Z1 direction) in the figure as shown in FIG.

  In the present embodiment, the first lens surface 2a is a convex surface protruding outward, and the second lens surface 2b is a concave surface recessed inward. On the first lens surface 2a, the light incident from the outside and transmitted through the first lens surface 2a converges (condenses), and the light incident from the outside and reflected by the first lens surface 2a is Diffuse (diverge).

  In addition, in the second lens surface 2b, light that is transmitted through the first lens surface 2a and incident on the second lens surface 2b is diffused both when transmitted through the second lens surface 2b and when reflected. To do.

  As shown in FIG. 2, the first lens surface 2 a and the second lens surface 2 b have the same optical axis 3 h, and the optical axis 3 h is formed to coincide with the central axis 3 f of the lens barrel 3. That is, the optical axis 3h is also the optical axis of the window lens 1 with a lens barrel.

  In the present embodiment, the lens barrel 3 is cylindrical, but is not limited to this. The lens barrel 3 can also have a cylindrical structure that is polygonal in plan view. Although the window lens 2 is assumed to be a circle in plan view, the present invention is not limited to this. The window lens 2 can be an ellipse or a polygon in plan view.

  Although the window lens 2 is formed of transparent glass, the present invention is not limited to this. If it is transparent, a resin or the like is also possible.

  The outer diameter of the window lens 2 is, for example, about 0.5 mm to 2.0 mm. The curvature radius of the first lens surface 2a is, for example, about 1.0 mm to 2.0 mm, and the curvature radius of the second lens surface 2b is, for example, about 0.1 mm to 1.0 mm. The outer diameter of the lens barrel 3 is, for example, about 2.0 mm to 3.0 mm.

  As shown in FIG. 3, the optical module 10 in the first embodiment has a housing 13, and a semiconductor laser 11, which is a light emitting element that emits light from the left side of the figure, and a collimating lens 12 in the housing 13. And is housed. The housing 13 is filled with an inert gas such as helium, and the lens barrel-equipped window lens 1 is hermetically fixed to the right end 13 b of the housing 13. By filling the inert gas, oxidation of the emission part of the semiconductor laser 11 is prevented.

  As shown in FIG. 3, the base 11 a is fixed on the bottom surface 13 a in the housing 13. The semiconductor laser 11 is fixed on the pedestal 11a with its emitting part facing the right side of the figure.

  The semiconductor laser 11 emits diffused light 14a toward the right side of the figure. The diffused light 14a emitted from the semiconductor laser 11 is converted into parallel light 14b by the collimator lens 12, and the parallel light 14b travels in the right direction in the figure.

  And the window lens 1 with a lens barrel fixed to the edge part 13b of the housing 13 is installed ahead of the parallel light 14b. The lens barrel-equipped window lens 1 is installed with the first lens surface 2a facing the semiconductor laser 11 and the second lens surface 2b facing outward.

  In the optical module 10 of the present embodiment, as shown in FIG. 3, the semiconductor laser 11 and the collimating lens 12 are fixed in the housing 13 so that the optical axes 15 coincide. Next, the lens barrel-equipped window lens 1 is fixed to the housing 13 so that the optical axis 15 and the optical axis 3h (illustrated in FIG. 2) of the lens barrel-equipped window lens 1 coincide with each other. In the following, the optical axis 15 is the optical axis of the optical module 10.

  In the optical module 10 of this embodiment, the optical axes of the semiconductor laser 11, the collimating lens 12, and the window lens 1 with the lens barrel are made to coincide with each other, but the present invention is not limited to this. It is also possible that the optical axes of the semiconductor laser 11 and the window lens 1 with a lens barrel are aligned with each other, and the optical axes of the collimating lens 12 and the window lens 1 with a lens barrel are provided in parallel.

  In the window lens 2, when the parallel light 14b is incident on the first lens surface 2a, the parallel light 14b becomes the convergent light 14c when passing through the first lens surface 2a. The convergent light 14c becomes parallel light 14d when transmitted through the second lens surface 2b. Thus, the first lens surface 2a and the second lens surface 2b of the window lens 2 are provided.

  Therefore, the diffused light 14 a emitted from the semiconductor laser 11 becomes parallel light 14 b when transmitted through the collimator lens 12, and becomes parallel light 14 d when transmitted through the window lens 2, and travels along an optical path 16 parallel to the optical axis 15. At that time, the parallel light 14d travels with the center of the parallel light 14d substantially aligned with the optical axis 15.

  It will be described that the optical coupling between the reflected return light and the semiconductor laser 11 is suppressed by this embodiment. FIG. 4 is an explanatory diagram of the reflected return light in the first embodiment. In the present embodiment, as shown in FIG. 4, the semiconductor laser 11, the collimating lens 12, and the window lens 2 are adjusted in optical axis as described above. Therefore, the reflected return light is focused on the emitting portion of the semiconductor laser 11 only when returning to the collimating lens 12 with parallel light. When the reflected return light returns to the collimating lens 12 with diffused light or convergent light, the condensing position, that is, the condensing points 14g and 14h deviate from the emitting part of the semiconductor laser 11.

  As shown in FIG. 4, the reflected return light 14e generated when the parallel light 14b is reflected by the first lens surface 2a is collimated while diffusing since the first lens surface 2a has a convex surface facing the parallel light 14b. Proceed toward the lens 12. Therefore, the reflected return light 14e enters the collimating lens 12 while being diffused, and is collected at a condensing point 14g on the left side of the drawing from the emitting portion of the semiconductor laser 11. That is, the reflected return light 14e is not condensed on the emission part of the semiconductor laser 11, but returns to the emission part of the semiconductor laser 11 in a diffused state.

  The reflected return light 14f generated by reflecting the convergent light 14c on the second lens surface 2b has a convex surface directed toward the convergent light 14c as shown in FIG. 1 is incident on the lens surface 2a. Next, when the light passes through the first lens surface 2a, the light advances toward the collimating lens 12 while diffusing. Therefore, the reflected return light 14f enters the collimating lens 12 while diffusing, and when it passes through the collimating lens 12, it is condensed at a condensing point 14h on the left side of the drawing from the condensing point 14g. Therefore, the reflected return light 14f returns to the emitting part of the semiconductor laser 11 in a diffused state.

  Thus, since the optical paths of the reflected return lights 14e and 14f are different from the optical path of the light emitted from the semiconductor laser 11 as the light emitting element except for the vicinity of the optical axis 15, the reflected return lights 14e and 14f are the semiconductor lasers. The light is not condensed on the 11 exit portions. Therefore, according to the present embodiment, the optical coupling between the reflected return lights 14e and 14f and the semiconductor laser 11 can be suppressed.

  According to the present embodiment, as shown in FIG. 4, the collimating lens 12 and the window lens 2 are connected by the parallel light 14b. Therefore, even if the distance between the collimating lens 12 and the window lens 2 is changed, the optical module is used. The influence on the parallel light 14d emitted from 10 is small. However, if the distance between the collimating lens 12 and the window lens 2 is changed, the positions of the condensing points 14g and 14h can be moved in the horizontal direction in the drawing. Therefore, according to the present embodiment, it is possible to adjust the optical coupling between the reflected return lights 14e and 14f and the semiconductor laser 11 while suppressing the influence on the parallel light 14d.

  FIG. 5 shows an example in which the optical module according to the first embodiment is used for optical communication. When the optical module 10 is used for optical communication, the parallel light 14 d is optically coupled to the end face 33 a of the optical fiber 33 by the condenser lens 32 as shown in FIG.

  According to the present embodiment, the reflected return light 14e is obtained in a state where the optical axes 15 of the semiconductor laser 11, the collimating lens 12, and the window lens 2 are matched, that is, without tilting the window lens 2 with respect to the optical axis 15. , 14f and the semiconductor laser 11 can be suppressed. Therefore, in the present embodiment, the parallel light 14d transmitted through the window lens 2 travels with the center of the parallel light 14d substantially coincident with the optical axis 15.

  Therefore, according to this embodiment, the optical axis of the optical module 10 and the condenser lens 32 can be adjusted in a state where the optical axis 35 of the condenser lens 32 is aligned with the optical axis 15 of the optical module 10. it can. The optical axis 15 and the optical axis 35 can be arranged linearly as shown in FIG.

  Therefore, according to the present embodiment, it is not necessary to adjust the optical axis by shifting the optical axis 35 of the condenser lens 32 from the optical axis 15 of the optical module 10, so that assembly is simple.

  Further, according to the present embodiment, it is not necessary to adjust the optical axis by shifting the optical axis, so that an error caused by this shifting does not occur. Therefore, the semiconductor laser 11 can be optically coupled to the end face 33a of the optical fiber 33, and the optical performance is excellent.

  Next, the manufacturing method of the window lens 1 with a lens barrel in the present embodiment will be described. FIG. 6 is an explanatory diagram of a method for manufacturing a window lens with a lens barrel in the first embodiment.

  In the step shown in FIG. 6A, the press device 50 is prepared. The press device 50 includes a body mold 53, an upper mold 51, a lower mold 52, and a heater 54. The upper mold 51 and the lower mold 52 include projecting portions 51a and 52a that project from the flat base surfaces 51b and 52b, respectively.

  The central axis of the upper mold 51 and the central axis of the lower mold 52 are provided so as to coincide with each other. The base surfaces 51b and 52b are provided so as to be orthogonal to these central axes.

  Next, in the step shown in FIG. 6B, the lens barrel 3 and the window material 2 e are placed in the barrel mold 53. At this time, the lens barrel 3 has the protruding portion 52a inserted into the inner peripheral surface thereof, and the window material 2e is placed on the protruding portion 52a. The heater 54 is heated to a temperature at which the window material 2e is softened.

  The lens barrel 3 has an upper surface 3g orthogonal to the central axis 3f of the lens barrel 3, as shown in FIG. The lens barrel 3 is placed with the upper surface 3g in contact with the base surface 52b. Therefore, the central axis 3 f of the lens barrel 3 substantially coincides with the central axis of the upper mold 51 and the central axis of the lower mold 52.

  Next, in the step shown in FIG. 6C, the upper mold 51 and the lower mold 52 are moved substantially parallel to the respective central axes to press the window material 2e from above and below. As a result, the shape of the upper mold 51 and the lower mold 52 is transferred to the window material 2e, whereby the window lens 1 with a lens barrel is formed.

  In this way, in the window lens 1 with the lens barrel, the central axes of the first lens surface 2a and the second lens surface 2b, that is, the optical axis 3h (shown in FIG. 2) are the central axes 3f ( 2) and is formed so as to be orthogonal to the upper surface 3g.

  Next, in the step shown in FIG. 6D, the heater 54 is turned off and cooled to a predetermined temperature. Then, the upper mold 51 and the lower mold 52 are pulled out from the body mold 53, and the window lens 1 with the lens barrel is released from the upper mold 51 and the lower mold 52, whereby the window lens 1 with the lens barrel is formed. Manufactured.

  As described above, according to the present embodiment, the lens barrel-attached window lens 1 is integrally molded by using only the lens barrel 3 and the window material 2e as members and press molding using a mold. According to the present embodiment, the window lens 1 with the lens barrel is integrally formed only with the lens barrel 3 and the window material 2e, but the present invention is not limited to this. It is possible to manufacture the window lens 1 with the lens barrel by bonding the lens barrel 3 manufactured by cutting from stainless steel or the like and the window lens 2 press-molded from the glass member with an adhesive member such as low-melting glass. It is.

  As shown in FIG. 3, the optical module 10 in the first embodiment includes a semiconductor laser 11, a housing 13 that houses a collimating lens 12, and a window lens 1 with a lens barrel manufactured as described above, such as helium. It is manufactured by fixing in an inert gas atmosphere.

  The housing 13 is formed with a joint surface 13 c orthogonal to the optical axis 15 of the semiconductor laser 11 and the collimating lens 12. As described above, the window lens 1 with the lens barrel is formed such that the upper surface 3g is orthogonal to the optical axes 3h of the first lens surface 2a and the second lens surface 2b.

  Therefore, according to this embodiment, when the window lens 1 with the lens barrel is fixed to the housing 13, the optical axis of the semiconductor laser 11 and the collimating lens 12 is fixed by bringing the upper surface 3g into contact with the bonding surface 13c and fixing it. 15 and the optical axis 3h of the window lens 1 with the lens barrel can be easily matched.

<Modification>
FIG. 7 shows a modification of the optical module in the first embodiment. FIG. 8 shows an example in which the modified optical module is used for optical communication. This modification is a case where the collimating lens 12 is removed from the optical module 10 of the first embodiment. That is, the optical module of the present modification is configured to include the semiconductor laser 11 and the window lens 2. The semiconductor laser 11 and the window lens 2 have the optical axis 15 coincident.

  As shown in FIG. 7, when the diffused light 18a emitted from the semiconductor laser 11 passes through the window lens 2, it is emitted to the outside as diffused light 18d. At this time, the reflected return lights 18b and 18c generated when the diffused light 18a is reflected by the first lens surface 2a and the second lens surface 2b are diffused by the first lens surface 2a and the second lens surface 2b. Since the convex surface is directed to 18a, it proceeds toward the semiconductor laser 11 while diffusing. Therefore, the reflected return lights 18b and 18c are not condensed on the emission part of the semiconductor laser 11, but return to the emission part of the semiconductor laser 11 in a diffused state.

  Therefore, according to the present modification, the optical coupling between the reflected return lights 18b and 18c and the semiconductor laser 11 can be suppressed.

  The case where the optical module of this modification is used for optical communication will be described. As shown in FIG. 7, when the diffused light 18a emitted from the semiconductor laser 11 passes through the window lens 2, it is emitted to the outside as diffused light 18d. Therefore, as shown in FIG. 8, in order to optically couple the diffused light 18d to the end face 33a of the optical fiber 33, the collimator lens 12 for making the diffused light 18d parallel light and the parallel light into the optical fiber. The condensing lens 32 for condensing on the end surface 33a of 33 is required.

  At this time, the optical module, the collimating lens 12, the condensing lens 32, and the optical fiber of the present modification are made in a state where the optical axes of the collimating lens 12 and the condensing lens 32 are aligned with the optical axis 15 of the window lens 2. The optical axis of the end surface 33a of 33 can be adjusted.

  Therefore, according to this modification, it is not necessary to adjust the optical axis by shifting the optical axes of the collimating lens 12, the condenser lens 32, and the optical fiber 33 from the optical axis 15 of the window lens 2. .

  Moreover, according to this modification, it is not necessary to adjust the optical axis by shifting the optical axis, so that an error caused by this shifting does not occur. Therefore, the semiconductor laser 11 can be coupled to the end face 33a of the optical fiber 33 optically efficiently, that is, with reduced coupling loss, and the optical performance is excellent.

<Second Embodiment>
FIG. 9 shows an optical module according to the second embodiment. FIG. 10 is an explanatory diagram of the reflected return light in the second embodiment. In the optical module 20 of the present embodiment, as shown in FIG. 9, the window lens 1 with a lens barrel is a convex second lens surface with the concave first lens surface 2 a facing the semiconductor laser 11 side. 2b is facing outward. The only difference between the present embodiment and the first embodiment is that the shapes of the first lens surface 2a and the second lens surface 2b are different, and the others are substantially the same.

  In this embodiment, the outer diameter of the window lens 2 is, for example, about 0.5 mm to 2.0 mm. The curvature radius of the first lens surface 2a is, for example, about 0.1 mm to 1.0 mm, and the curvature radius of the second lens surface 2b is, for example, about 1.0 mm to 2.0 mm. The outer diameter of the lens barrel 3 is, for example, about 2.0 mm to 3.0 mm.

  In the present embodiment, it will be described that the optical coupling between the reflected return light and the semiconductor laser 11 is suppressed. In the present embodiment, as shown in FIG. 10, the optical axes of the semiconductor laser 11, the collimator lens 12, and the window lens 2 that are light emitting elements are adjusted. Therefore, the reflected return light is focused on the emitting portion of the semiconductor laser 11 only when returning to the collimating lens 12 with parallel light. When the reflected return light returns to the collimating lens 12 with diffused light or convergent light, the condensing positions, that is, the condensing points 14m and 14n are out of the emitting part of the semiconductor laser 11.

  As shown in FIG. 10, the diffused light emitted from the semiconductor laser 11 is converted into parallel light 14 b by the collimator lens 12. The reflected return light 14i generated when the parallel light 14b is reflected by the first lens surface 2a is focused on the collimating lens 12 while converging because the first lens surface 2a has a concave surface with respect to the parallel light 14b. Proceed toward. Therefore, the reflected return light 14 i is incident on the collimating lens 12 while converging and passes through the collimating lens 12, and then converges on a condensing point 14 m between the collimating lens 12 and the semiconductor laser 11. And after condensing, it advances toward the semiconductor laser 11 while diffusing. Therefore, the reflected return light 14i returns to the emission part of the semiconductor laser 11 in a diffused state.

  As shown in FIG. 10, when the parallel light 14b passes through the first lens surface 2a, it changes to diffused light 14w that travels toward the second lens surface 2b while diffusing. The reflected return light 14k generated when the diffused light 14w is reflected by the second lens surface 2b is focused on the first lens while converging because the second lens surface 2b faces the concave surface with respect to the diffused light 14w. Proceed toward the surface 2a. Next, when passing through the first lens surface 2a, it proceeds toward the collimating lens 12 while converging. Therefore, the reflected return light 14k enters the collimating lens 12 while converging, and is collected at the condensing point 14n on the right side of the drawing with respect to the condensing point 14m. That is, the reflected return light 14k is not condensed on the emission part of the semiconductor laser 11, but returns to the emission part of the semiconductor laser 11 in a diffused state.

  Thus, since the optical paths of the reflected return lights 14i and 14k are different from the optical path of the light emitted from the semiconductor laser 11 as the light emitting element except for the vicinity of the optical axis 15, the reflected return lights 14i and 14k are the semiconductor lasers. The light is not condensed on the 11 exit portions. Therefore, according to the present embodiment, the optical coupling between the reflected return lights 14i and 14k and the semiconductor laser 11 can be suppressed.

  According to the present embodiment, as shown in FIG. 10, the collimating lens 12 and the window lens 2 are connected by the parallel light 14b, so that the optical module can be obtained even if the distance between the collimating lens 12 and the window lens 2 is changed. 20 (shown in FIG. 9) has a small influence on the parallel light 14d. However, if the distance between the collimating lens 12 and the window lens 2 is changed, the positions of the condensing points 14m and 14n can be moved in the horizontal direction in the drawing. Therefore, according to the present embodiment, as in the first embodiment, it is possible to adjust the optical coupling between the reflected return lights 14i and 14k and the semiconductor laser 11 while suppressing the influence on the parallel light 14d.

  According to the present embodiment, as shown in FIGS. 9 and 10, the optical axis 15 of the semiconductor laser 11, the collimating lens 12, and the window lens 2 is aligned, that is, the window lens with respect to the optical axis 15. The optical coupling between the reflected return lights 14i and 14k and the semiconductor laser 11 can be suppressed without tilting 2. Therefore, in the present embodiment, the parallel light 14d transmitted through the window lens 2 travels with the center of the parallel light 14d substantially coincident with the optical axis 15.

  Therefore, according to this embodiment, the optical axis of the condensing lens which condenses the optical module 20 on the end surface of the optical fiber is made to coincide with the optical axis 15 of the optical module 20 as in the first embodiment. Thus, the optical axis can be adjusted. Therefore, according to this embodiment, it is not necessary to adjust the optical axis by shifting the optical axis of the condensing lens from the optical axis 15, so that the assembly is simple.

  Further, according to the present embodiment, it is not necessary to adjust the optical axis by shifting the optical axis, so that an error caused by this shifting does not occur. Therefore, the semiconductor laser 11 can be optically efficiently coupled to the end face of the optical fiber, that is, coupled with reduced coupling loss, and the optical performance is excellent.

  The positions and positional relationships of the condensing points 14m, 14n, etc. include the curvature radii of the first lens surface 2a and the second lens surface 2b, and the inter-surface distance between the first lens surface 2a and the second lens surface 2b. Varies depending on etc. In the present embodiment, these values are selected so as to be the modes shown in FIG. 10 and FIG. 11, but the present invention is not limited to this.

<First Modification>
FIG. 11 is an explanatory diagram of reflected return light in the first modification example of the second embodiment. In this modification, the reflected return light 14i is closer to the first lens surface 2a side than the midpoint of the distance between the surfaces of the collimating lens 12 facing the window lens 2 and the first lens surface 2a. A distance between the collimating lens 12 and the window lens 2 is provided so as to have a focal point, that is, a condensing point 14p.

  Even if the distance between the collimating lens 12 and the window lens 2 is increased, the influence on the parallel light 14d emitted from the window lens 2 to the outside is small. Therefore, in this modification, the influence on the parallel light 14d emitted to the outside is suppressed, and the midpoint of the distance between the surfaces of the collimating lens 12 facing the window lens 2 and the first lens surface 2a is determined. Also, it is possible to provide a condensing point 14p at a position close to the first lens surface 2a side.

  By appropriately selecting the radius of curvature of the first lens surface 2a, the first lens surface is more than the midpoint of the distance between the surfaces of the collimating lens 12 facing the window lens 2 and the first lens surface 2a. It is possible to provide the condensing point 14p at a position close to the 2a side.

  As shown in FIG. 11, the reflected return light 14i generated by reflecting the parallel light 14b on the first lens surface 2a is condensed at the condensing point 14p and then travels toward the collimating lens 12 while diffusing. Next, when the light passes through the collimating lens 12, the light is condensed at a condensing point 14 s located on the left side in the drawing from the emission part of the semiconductor laser 11. That is, the reflected return light 14i is not condensed on the emission part of the semiconductor laser 11, but returns to the emission part of the semiconductor laser 11 in a diffused state.

  The reflected return light 14k generated by reflecting the diffused light 14w by the second lens surface 2b travels toward the first lens surface 2a while converging. Next, when the light passes through the first lens surface 2a, the light converges, converges on the condensing point 14q, and then proceeds toward the collimating lens 12 while diffusing. Therefore, the reflected return light 14k enters the collimating lens 12 while diffusing, and is collected at a condensing point 14r located on the left side in the drawing with respect to the emitting portion of the semiconductor laser 11. That is, the reflected return light 14k is not condensed on the emission part of the semiconductor laser 11, but returns to the emission part of the semiconductor laser 11 in a diffused state.

  At this time, the condensing point 14p and the condensing point 14q are closer to the first lens surface 2a than the midpoint of the distance between the surface of the collimating lens 12 facing the window lens 2 and the first lens surface 2a. By providing in the close position, the reflected return light 14i and the reflected return light 14k enter the collimating lens 12 in a more diffused state. As a result, the reflected return light 14i and the reflected return light 14k return to the emission part of the semiconductor laser 11 in a more diffused state.

  Therefore, according to this modification, the optical coupling between the reflected return lights 14i and 14k and the semiconductor laser 11 can be further suppressed.

  Furthermore, it is also possible to provide the condensing point 14p and the condensing point 14q so that the reflected return light 14i and the reflected return light 14k enter the collimating lens 12 in a more diffuse state. In this case, some of the reflected return light 14 i and the reflected return light 14 k pass outside the collimating lens 12. If provided in this way, part of the reflected return light 14 i and the reflected return light 14 k that pass outside the collimating lens 12 cannot return to the semiconductor laser 11.

  Therefore, in such a case, the optical coupling between the reflected return lights 14i and 14k and the semiconductor laser 11 can be further suppressed.

DESCRIPTION OF SYMBOLS 1 Window lens with lens barrel 2 Window lens 2a 1st lens surface 2b 2nd lens surface 3 Lens barrel 3a Opening part 3f Center axis 3g Top surface 3h, 15 Optical axis 10, 20 Optical module 11 Semiconductor laser 11a Base 12 Collimating lens 13 Housing 13a Bottom surface 13b End portion 13c Joint surface 14a, 14h Diffused light 14b, 14d Parallel light 14c Converging light 32 Condensing lens 33 Optical fiber 33a End surface

Claims (3)

A light emitting element that emits light;
An optical module comprising: a window lens that transmits the light; and the light transmitted through the window lens is emitted to the outside.
The window lens includes a first lens surface on a front surface thereof and a second lens surface on a rear surface thereof, and the light axes of the light emitting element and the window lens are provided so as to coincide with each other. An optical module having a lens surface facing the light emitting element, wherein one of the first lens surface and the second lens surface is a convex surface and the other is a concave surface. Having a collimating lens for collimating the light;
The collimating lens is provided between the light emitting element and the window lens, the optical axes of the collimating lens and the window lens are provided in parallel, and the first lens surface is a convex surface, The optical module according to claim 1, wherein the second lens surface is a concave surface.   The collimating lens which makes the 1st lens surface concave, the 2nd lens surface convex, and makes the emitted light of the light emitting element parallel light is provided between the light emitting element and the window lens. In addition, the light axes of the light emitting element, the collimating lens, and the window lens are provided so that the reflected light reflected by the first lens surface is focused between the collimating lens and the window lens. And the focal point is located closer to the first lens surface than the midpoint of the distance between the surfaces of the collimating lens facing the window lens and the first lens surface. The optical module according to claim 1.

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