Optical multiplexing device

Abstract

Provided is an optical multiplexing device capable of: multiplexing a plurality of light beams; reducing the diffusion angle of emitted light as compared with the prior art; and improving light-utilization efficiency. This optical multiplexing device comprises: a plurality of incident ports into which a plurality of light beams respectively enter; a single emission port from which light obtained by multiplexing the plurality of light beams is emitted; a first intersection region in which one light beam that has entered from the incident port intersects with another light beam; a reflection surface on which the one light beam that has passed through the first intersection region is reflected; and a second intersection region in which the one light beam reflected by the reflection surface crosses the other light beam again.

Description

Optical multiplexer

[0001] The present invention relates to an optical multiplexing device.

[0002] Conventionally, projector devices and display devices using light sources such as laser light-emitting elements have been known. For example, a projector device is known that uses a condenser lens to condense light emitted from a light source such as a PLC (planar light circuit) onto a screen to generate a minute spot of light. In this device, an MEMS mirror disposed between the condenser lens and the screen is vibrated within a predetermined angle to scan the spot of light on the screen, thereby forming an image. This type of projector is not only used in MEMS scan projectors, but also in other types such as LCOS, DMD, and vector scan projectors. Furthermore, this type of projector is used not only in projectors but also in a wide range of applications, such as light sources for confocal microscopes, sensing, and illumination.

[0003] Optical multiplexing devices have been proposed as devices that can multiplex a plurality of light beams and use them as a light source (see, for example, Patent Documents 1 and 2).

[0004] JP2020-154335A JP10-142434A

[0005] However, when the spread (diffusion angle) of light emitted from the light source is large, vignetting occurs at the condenser lens and mirror, resulting in a problem of reduced light utilization efficiency. Also, when the area size of the light emitted from the light source is relatively large, the diameter of the spot light generated on the screen by the condenser lens becomes large, resulting in a problem of not being able to obtain a high-definition image.

[0006] The technology disclosed in Patent Document 1 involves connecting multiple optical waveguides extending in one direction at a predetermined angle and combining the incident light beams, but this method results in the formation of an acute-angled portion in the combining region. Since it is practically impossible to create such an acute angle, a flat portion of approximately 3 μm is required between the optical waveguides. This poses a problem in that it is theoretically difficult to make the combining angle of the light beams smaller than the predetermined angle.

[0007] The technology disclosed in Patent Document 2 relates to an optical multiplexing element that multiplexes a first light beam from a first input optical waveguide and a second light beam from a second input optical waveguide, which is substantially perpendicular to the first input optical waveguide, by making the first light beam incident on an output optical waveguide via a reflecting surface. This method requires that the optical axis of the multiplexed light beam be positioned between the optical axes of the first and second light beams. Therefore, as the number of light beams to be multiplexed increases, the area size of the output aperture increases. Therefore, depending on the magnification of the lens that focuses the output light, the focused spot becomes larger, resulting in a problem of reduced light utilization efficiency.

[0008] The present invention has been made in consideration of the above, and aims to provide an optical multiplexing device that can reduce the diffusion angle of the emitted light and the size of the exit port compared to conventional devices, thereby improving light utilization efficiency.

[0009] (1) The present invention relates to an optical multiplexing device capable of multiplexing a plurality of light beams, the optical multiplexing device having a plurality of entrance ports through which the plurality of light beams are respectively incident, and a single exit port through which light resulting from the multiplexing of the plurality of light beams is emitted, the optical multiplexing device having a first intersection region where one light beam incident from the entrance port intersects with another light beam, a reflecting surface where the one light beam that has passed through the first intersection region is reflected, and a second intersection region where the one light beam reflected by the reflecting surface intersects again with the other light beam.

[0010] (2) An optical multiplexing device according to (1), comprising a multiplexing path through which the plurality of light beams are multiplexed, the rear end of the multiplexing path being connected to another multiplexing path at a subsequent stage or being provided with the exit port, the inclination angle of the reflecting surface with respect to the light beams entering from the entrance port being set so that the second intersection region is at the connection point with the other multiplexing path or at the position of the exit port, and the multiplexing angle, which is the angle between the one light beam reflected by the reflecting surface and the other light beam, is 0.23° or less.

[0011] (3) The optical multiplexing device according to (1) or (2), comprising a waveguide having the inlet and a multiplexing path connected to the waveguide at a predetermined angle, the length of the waveguide being 1.5 mm or less.

[0012] (4) An optical multiplexing device according to any one of (1) to (3), comprising: a first optical path unit having the entrance; a second optical path unit having the entrance, the first intersection region, the reflecting surface, and the second intersection region; and a third optical path unit having the entrance, the first intersection region, the reflecting surface, the second intersection region, and the exit; wherein one or more of the second optical path units are provided as needed.

[0013] According to the present invention, it is possible to provide an optical multiplexing device that can reduce the divergence angle of emitted light compared to conventional devices and improve the light utilization efficiency.

[0014] FIG. 1 is a schematic diagram showing the configuration of an optical multiplexing device according to a first embodiment; FIG. 2 is an enlarged view of a main part of FIG. 1; FIG. 3 is a schematic diagram showing a configuration for inputting light to an incident port according to the first embodiment; FIG. 4 is a schematic diagram showing the configuration of an optical multiplexing device according to a comparative example 1; FIG. 5 is a diagram showing the simulation results of an optical multiplexing device according to a comparative example 1; FIG. 6 is a diagram showing the simulation results of an optical multiplexing device according to a second embodiment; FIG. 7 is a diagram showing the simulation results of an optical multiplexing device according to a third embodiment; and FIG. 8 is a diagram showing the simulation results of an optical multiplexing device according to a fourth embodiment.

[0015] An embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the description of the embodiment below.

[0016] First Embodiment Configuration of Optical Multiplexing Device As shown in FIG. 1 , the optical multiplexing device 1 according to this embodiment is a device capable of multiplexing multiple light beams, namely, light beams L10, L20, and L30, and outputting output light L5. The light beams L10, L20, and L30 enter the optical multiplexing device 1 through the light entrances 11a, 21a, and 31a, respectively, are multiplexed within the optical multiplexing device 1, and are output as output light L5. In this specification and claims, the multiple light beams may be multiple light beams that are independent of wavelength. In other words, at least one set of the multiple light beams may have the same wavelength. Note that the multiple light beams may all have different wavelengths. In this embodiment, the light beams L10, L20, and L30 are not particularly limited, and may be, for example, red light, blue light, and green light, respectively.

[0017] 1 to 5, the position of the arrows indicating each light ray indicates the position of the optical axis of each light ray. Furthermore, the above drawings are exaggerated schematic diagrams to clearly show the relationship and angles between the light rays, and do not faithfully represent the configuration of an actual optical multiplexing device.

[0018] The medium constituting the optical multiplexing device 1 is not particularly limited as long as it is a material that can transmit light with low loss, and may be made of, for example, glass, silicon, etc. The structure of the optical multiplexing device 1 can be manufactured, for example, by a known semiconductor manufacturing process. Furthermore, the medium may be a gas such as air, in which case the optical multiplexing device will have a hollow mirror-like shape with a mirrored inner surface on the optical path.

[0019] The optical multiplexing device 1 has optical path units 10, 20, and 30 corresponding to the light beams L10, L20, and L30, respectively. FIG. 1 shows an optical multiplexing device 1 that multiplexes light beams of three different wavelengths. However, in the present disclosure, the number of multiplexed light beams is not particularly limited as long as it is two or more. If an optical multiplexing device that multiplexes light beams of two different wavelengths is to be configured, an optical multiplexing device can be configured that does not have an optical path unit 20, but has an optical path unit 10 and an optical path unit 30 connected together. If an optical multiplexing device that multiplexes light beams of four or more different wavelengths is to be configured, an optical multiplexing device can be configured that has an optical path unit 10, a plurality of optical path units 20 corresponding to the number of light beams to be multiplexed, and an optical path unit 30.

[0020] In FIG. 1 , the optical path unit 10 includes a waveguide 11 and a waveguide 12. The waveguide 11 has an entrance 11a through which a light ray L10 is incident. The waveguide 11 and the waveguide 12 are connected at a substantially right angle in FIG. 1 . A reflecting surface R1 is formed on the surface of the connection portion facing the waveguide 11. The light ray L10 incident from the entrance 11a passes through the interior of the waveguide 11 (light ray L11), is reflected by the reflecting surface R1, and enters the waveguide 12 (light ray L12). The angle of the reflecting surface R1 may be set so that the optical axis of the light ray L12 reflected by the reflecting surface R1 is guided in a direction along the optical path of the waveguide 12 and passes through approximately the center of the waveguide 12. Therefore, the angle at which the waveguide 11 and the waveguide 12 are connected may be any angle. However, the angle of the reflecting surface R1 must be set so as to exceed the critical angle of the medium (so as to cause total reflection at the reflecting surface), and the same applies to the following reflecting surfaces. The waveguide 12 is connected to the multiplexing path 22 of the optical path unit 20, and the light ray L12 is incident on the multiplexing path 22.

[0021] The optical path unit 10 does not need to have the waveguide 11. In this case, the light ray L10 can be made incident directly on the connection surface of the waveguide 12 with the waveguide 11 in Fig. 1. When the optical path unit 10 has the waveguide 11, the position at which the light beam is incident becomes clear as a shape of the waveguide, which makes it easier to assemble and adjust the actual device.

[0022] The optical path unit 10 does not need to have the reflecting surface R1. In this case, instead of the waveguides 11 and 12, a single linear waveguide 12 may be used, and an entrance may be provided at the end face of the waveguide 12. On the other hand, since the optical path unit 10 has the reflecting surface R1, the position of the device that causes light to enter the entrance 11a can be set at any position.

[0023] Here, with reference to FIG. 3 , the configuration of a device for introducing light into the entrance 11a will be described. As shown in FIG. 3 , divergent light L1 emitted from light source B (maximum width of the light-emitting region: w40) is condensed by an input optical system C1 composed of a condensing lens or the like. The condensed light ray L10 enters the entrance 11a. In this case, if the lateral magnification of the input optical system C1 is β, the maximum width w41 of the light-emitting region image formed at the entrance 11a is w41 = w40 × β. Therefore, in order to ensure that the light beam emitted from light source B is incident on the entrance 11a without leakage, the width w3 of the entrance 11a must be larger than w41. When light source B is a single-mode LD, the width w3 of the entrance 11a is preferably 1.5 μm or greater. When light source B is a multi-mode LD, the width w3 of the entrance 11a is preferably 80 μm or greater.

[0024] The optical path unit 20 has a waveguide 21 and a multiplexing path 22. The number of optical path units 20 can be increased or decreased depending on the number of light beams to be multiplexed, and the optical path unit 20 may not be provided. The waveguide 21 has an entrance 21a through which the light ray L20 is incident. The waveguide 21 and the multiplexing path 22 are connected at a substantially right angle in FIG. 1. A reflecting surface R2 is formed on the surface of the connection portion facing the waveguide 21. The waveguide 12 is further connected to the connection portion. The waveguide 12 and the multiplexing path 22 are connected so as to extend in the same direction. The angle at which the waveguide 12 and the waveguide 21 are connected and the angle at which the waveguide 21 and the multiplexing path 22 are connected can be any angle. Like the optical path unit 10, the optical path unit 20 does not have to have a waveguide 21. In this case, the light ray L20 can be made to directly enter the connection surface between the waveguide 21 and the multiplexing path 22.

[0025] A light ray L20 incident from the light entrance 21a passes through the inside of the waveguide 21 (light ray L21), is reflected by the reflecting surface R2, and enters the multiplexing path 22 (light ray L22). The reflecting surface R2 is the reflecting surface that first reflects one of the light rays (light ray L21) incident from the light entrance. The angle of the reflecting surface R2 can be adjusted to any angle, similar to the reflecting surface R1. The multiplexing path 22 is connected to the multiplexing path 32 of the optical path unit 30.

[0026] Light ray L21 (one light ray) incident from the light entrance 21a intersects with light ray L12 (the other light ray) emitted from the preceding optical path unit 10 in a first intersection region F2 located at the connection between the waveguide 21 and the waveguide 12. Light ray L21 is then reflected by the reflecting surface R2 and propagates to the multiplexing path 22 (light ray L22). Light ray L22 reflected by the reflecting surface R2 again intersects with light ray L12 (the other light ray) in a second intersection region F21 and is multiplexed (light ray L4). Light ray L4 then enters the multiplexing path 32. Note that in this specification and claims, the positions where light rays intersect and the positions where light rays are reflected are positions relative to the optical axes of the respective light rays.

[0027] 1 , the second intersection region F21 is located at the rear end of the multiplexing path 22. However, this is not limiting, and the second intersection region F21 may be located within the multiplexing path 32. By locating the second intersection region F21 after the rear end of the multiplexing path 22, the number of reflections on the side surfaces of the optical path can be reduced, thereby narrowing the diffusion angle of the emitted light. The position of the second intersection region F21 can be set by adjusting the optical axis direction of the light ray L21, the angle of the reflecting surface R2, and the length of the multiplexing path 22.

[0028] As shown in FIG. 1 , the multiplexing path 22 is configured so that the optical path width on the side connected to the subsequent multiplexing path is smaller than the optical path width on the side where the reflecting surface R2 is provided. Specifically, the optical path width of the multiplexing path 22 narrows linearly in proportion to the length from the reflecting surface R2 to the connection with the multiplexing path 32. Because the multiplexing position is located near the connection with the multiplexing path 32, the light beam reflected by the reflecting surface R2 propagates from the reflecting surface R2 to the multiplexing path 32 without being reflected by the side surfaces of the waveguide. On the other hand, it is known in principle that the divergence angle of the emitted light increases when the number of reflections of the light beam on the side surfaces of the waveguide increases. Therefore, the above configuration can theoretically narrow the divergence angle of the emitted light.

[0029] The optical path unit 30 has a waveguide 31 and a multiplexing path 32. The waveguide 31 has an entrance 31a through which the light ray L30 is incident. The waveguide 31 and the multiplexing path 32 are connected at approximately a right angle in FIG. 1 . A reflecting surface R3 is formed on the surface of the connection portion facing the waveguide 31. The multiplexing path 22 is further connected to the connection portion. The multiplexing path 22 and the waveguide 31 are connected so as to extend in the same direction. The angle at which the multiplexing path 22 and the waveguide 31 are connected and the angle at which the waveguide 31 and the multiplexing path 32 are connected can be any angle.

[0030] A light ray L30 incident from the light entrance 31a passes through the inside of the waveguide 31 (light ray L31), is reflected by the reflecting surface R3, and enters the multiplexing path 32 (light ray L32). The reflecting surface R3 is the reflecting surface that first reflects one of the light rays (light ray L31) incident from the light entrance. The angle of the reflecting surface R3 can be adjusted to any angle, similar to the reflecting surface R1. A single exit port 32a is formed at the end of the multiplexing path 32.

[0031] Light ray L31 (one light ray) incident from the light entrance 31a intersects with light ray L4 (the other light ray) emitted from the previous optical path unit 20 in a first intersection region F3 located at the connection between the waveguide 31 and the multiplexing path 32. Light ray L31 is then reflected by the reflecting surface R3 and propagates to the multiplexing path 32 (light ray L32). Light ray L32 reflected by the reflecting surface R3 again intersects with light ray L4 (the other light ray) in a second intersection region F4 and is multiplexed with the light ray L4 (the other light ray) (light ray L5). Light ray L5 is then emitted to the outside from the light exit 32a.

[0032] 1, the second intersection region F4 of the optical path unit 30 is preferably set to the position of the exit port 32a. This makes it possible to narrow the divergence angle of the emitted light (light ray L5). The position of the second intersection region F4 can be set by adjusting the optical axis direction of the light ray L31, the angle of the reflecting surface R3, and the length of the multiplexing path 32.

[0033] Here, referring to FIG. 2 , a preferred mode for combining two light rays (one light ray reflected by the reflecting surface and the other light ray emitted from the preceding optical path unit) in the second intersection region will be described. While FIG. 2 uses the optical path unit 30 as an example, a similar configuration can also be applied to the optical path unit 20. As shown in FIG. 2 , the angle A formed by the two light rays when the two light rays are combined is preferably 0.23° or less. This narrows the divergence angle of the combined light. The angle A can be adjusted by changing the reflecting surface inclination angle r3 of the reflecting surface R3 (the angle between the optical axis of the light incident from the entrance and the reflecting surface) and the length (optical path length) w2 of the multiplexing path 32.

[0034] The length (optical path length) w1 of the waveguide 31 is preferably 1.5 mm or less, which can minimize the loss of incident light. The same applies to the first optical path unit and the second optical path unit.

[0035] Although the preferred embodiments of the present invention have been described above, the content of the present invention is not limited to the above embodiments and can be modified as appropriate.

[0036] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0037] Example 1 Optical simulation was performed using the optical design software ZEMAX (registered trademark) (manufactured by ZEMAX Development Corporation) for an optical multiplexing device having a configuration similar to that of the optical multiplexing device 1 according to the first embodiment. The specific configuration of the optical multiplexing device in Example 1 is shown below. Red light was used as the light beam L10, blue light as the light beam L20, and green light as the light beam L30 (input lens: FLGSRSA21A manufactured by Alps Alpine Co., Ltd.). The length w1 (length w1 in FIG. 2) of the waveguides 11, 21, and 31 of each optical path unit was 1.259 mm. The length w2 (length w2 in FIG. 2) of the waveguide 12 and the multiplexing path 22 was 1.5 mm. The length w2 (length w2 in FIG. 2) of the multiplexing path 32 was 1.62 mm. The width w3 (length w3 in FIG. 2 ) of the waveguides 11, 12, 21, and 31 of each optical path unit was 5 μm. The maximum width (width on the front side) of the multiplexing path 22 and the multiplexing path 32 (width on the rear side) was 10 μm, and the minimum width (width on the front side) was 5 μm. The depth (length in the direction perpendicular to the paper surface in FIG. 1 ) of each waveguide and multiplexing path was 5 μm. That is, the cross section of the exit aperture was set to 5 μm x 5 μm. In the multiplexing path 22, the multiplexing angle (multiplexing angle A in FIG. 2 ) of the blue light with other light rays was 0.191° (reflecting surface inclination angle of reflecting surface R2: 45.096°). In the multiplexing path 32, the multiplexing angle (multiplexing angle A in FIG. 2 ) of the green light with other light rays was 0.177° (reflecting surface inclination angle of reflecting surface R3: 45.089°).

[0038] A detector (Detector 1) was placed immediately after the exit port of the optical multiplexing device of Example 1. An output lens (Edmund #84127, manufactured by Edmund Optics Japan, Inc.) was placed on the optical axis 2.6 mm away from the exit port, and a detector (Detector 2) was placed on the first surface (incident surface). A detector (Detector 3) was placed on the optical axis 17.547 mm away from the first surface. Figure 5 shows the intensity distribution of the output light detected by each detector. The vertical and horizontal axes in Figures 5 to 9 correspond to the detector size (unit: mm), and the center (vertical axis = 0, horizontal axis = 0) corresponds to the position of the optical axis. In each figure, darker areas indicate areas with high output light intensity.

[0039] [Examples 2 to 4] Optical multiplexing devices according to Examples 2 to 4 were constructed in the same manner as Example 1, except that the configuration of the optical multiplexing device was as shown in Table 1. Example 3 was constructed without providing waveguides 11, 21, and 31. In addition, optical simulations were performed using the optical multiplexing devices of Examples 2 to 4 with the same arrangement of detectors and output lenses as in Example 1. The intensity distributions of the output light are shown in FIG. 7 for Example 2, FIG. 8 for Example 3, and FIG. 9 for Example 4, respectively.

[0040] Comparative Example 1 The configuration of an optical multiplexing device 1b according to Comparative Example 1 is shown in FIG. 4. As shown in FIG. 4, the optical multiplexing device 1b includes an optical path unit 10B, an optical path unit 20B, and an optical path unit 30B. Each optical path unit includes a waveguide 11B, 21B, and 31B (optical path length: 1.259 mm) into which a light beam L10b (red light), a light beam L20b (blue light), and a light beam L30b (green light), respectively, are incident. The configuration of the optical path unit 10B is the same as that of the optical path unit 10, and includes a waveguide 12B. The configuration of the optical path units 20B and 30B differs from that of the optical path units 20 and 30 in that the incident light (one light beam) is reflected and multiplexed with the other light beam before passing through the first intersection region. With the above configuration, there is a limit to how small the multiplexing angle can be made. Waveguide multiplexers 22B and 32B multiplex multiple light beams with expanded waveguide widths W22b and W32b (both 18 μm). The waveguide width is then reduced to width wb1 (6 μm). Multiplexing angles r2b and r3b are both 1°. The multiplexed light beam L6 is emitted from exit port 32b. Other details of each configuration are shown in Table 1. However, the symbols in Table 1 (W1 to W3, etc.) use the symbols of the optical multiplexer 1 corresponding to the configuration of Comparative Example 1.

[0041] An optical simulation was carried out using the optical multiplexing device 1b according to the comparative example 1, with the detector and output lens arranged in the same manner as in the example 1. The intensity distribution of the output light is shown in FIG.

[0042] From the results of Figures 5 and 6, for example, when comparing the spread of the light beam on the detector 2, it is clear that the spread of the light beam in Example 1 is narrower than that in Comparative Example 1, and therefore the angle of diffusion of the emitted light is narrower than that in the Comparative Example.

[0043]

[0044] The light intensity values ​​reaching each detector in Examples 1 to 4 and Comparative Example 1 are shown in Table 2 below. In Table 2, the waveguide transmittance (%) means the light intensity value of light reaching detector 1 / light intensity value of the light source (%). The output lens conversion efficiency (%) means the light intensity value of light reaching detector 3 / light intensity value of light reaching detector 2 (%). The total light utilization efficiency (%) means the light intensity value of light reaching detector 3 / light intensity value of the light source (%).

[0045]

[0046] As shown in Table 2, compared to the optical multiplexer of Comparative Example 1, the optical multiplexers of each Example are clearly superior in terms of waveguide transmittance (%), output lens conversion efficiency (%), and total light utilization efficiency (%).

[0047] 1 Optical multiplexing device 11a, 21a, 31a Incident port F2, F3 First intersection region F21, F4 Second intersection region 22, 32 Waveguide 11, 21, 31 Waveguide 32a Emission port A Multiplexing angle 10 First optical path unit 20 Second optical path unit 30 Third optical path unit

Claims

1. An optical multiplexing device capable of multiplexing a plurality of light beams, comprising: a plurality of input ports into which the plurality of light beams are respectively incident; and a single output port from which the light obtained by multiplexing the plurality of light beams is emitted, having a first intersection region where one of the light beams incident from the input port intersects with the other light beam, a reflecting surface on which the one light beam passing through the first intersection region is reflected, and a second intersection region where the one light beam reflected by the reflecting surface intersects with the other light beam again.

2. Having a multiplexing path in which the plurality of light beams are multiplexed, the rear end of the multiplexing path is connected to another multiplexing path in a subsequent stage or the output port is provided, and the inclination angle of the reflecting surface with respect to the light beam incident from the input port is set such that the second intersection region becomes the connection portion with the other multiplexing path or the position of the output port, and the multiplexing angle, which is the angle formed by the one light beam reflected by the reflecting surface and the other light beam, is 0.23° or less. The optical multiplexing device according to claim 1.

3. Having a waveguide having the input port and a multiplexing path connected to the waveguide at a predetermined angle, and the length of the waveguide is 1.5 mm or less. The optical multiplexing device according to claim 1 or 2.

4. Having a first optical path unit having the input port, a second optical path unit having the input port, the first intersection region, the reflecting surface, and the second intersection region, and a third optical path unit having the input port, the first intersection region, the reflecting surface, the second intersection region, and the output port, and the second optical path unit is provided with one or more as required. The optical multiplexing device according to claim 1 or 2.

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