Optical coupler, optical coupling member, visible light source module, and optical engine

Abstract

To provide an optical coupler that can be connected to or integrated with an optical modulator using a lithium niobate film and can cope with a high output.SOLUTION: An optical coupler 100 includes one-input and two-output multimode interference input portions 60-1, 60-2, and 60-3 as light input portions of a laser beam for each laser beam. The optical coupler further includes: one light output port 22o through which three laser beams can be coupled and emitted; the total of six light input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, 21-32 of which two extend from each of the multimode interference input portions 60-1, 60-2, and 60-3; a light output side optical waveguide 22 that extends from the light output port 22o; and an optical coupling portion 50 to which the six light input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, 21-32 and the light output side optical waveguide 22 are connected.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical multiplexer, an optical multiplexing member, a visible light source module, and an optical engine. [Background technology]

[0002] Currently, glasses-type terminals are being considered for xR technologies such as VR (Virtual Reality) and AR (Augmented Reality). In particular, in recent years, retinal scanning displays that allow users to view images by forming an image on the user's retina with two-dimensionally scanned light have been attracting attention. In retinal scanning displays, three colors of visible light, generally emitted from light sources such as LEDs (Light Emitting Diodes) or LDs (Laser Diodes) corresponding to the colors R (red), G (green), and B (blue), are combined on one optical axis. The combined three colors of visible light are transmitted to an image display unit. The image display unit two-dimensionally scans the transmitted light and makes it enter the user's pupil. The user views the image as the incident light forms an image on the user's retina. In this case, the retina is the screen that displays the image.

[0003] For example, Patent Document 1 discloses the configuration of a retinal projection display using a Mach-Zehnder type optical modulator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6728596 [Patent Document 2] Patent No. 6787397 [Patent Document 3] Patent No. 6572377 [Patent Document 4] JP 2012-48071 A [Patent Document 5] JP 2020-27170 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the retinal projection display disclosed in Patent Document 1, multiple optical waveguides are arranged close to each other at the exit section, but they are not multiplexed, so the optical axis for each wavelength is different, making it difficult to control the exiting light.

[0006] Also, a visible light modulator using a lithium niobate film is disclosed in Patent Document 2. Although an RGB optical multiplexer that can be connected to or integrated with a visible light modulator using a lithium niobate film is required, it has not yet been studied.

[0007] Regarding multiplexing of visible light, directional couplers have generally been considered (for example, see Patent Document 3). These are made of glass-based materials and have excellent stability, but when using a lithium niobate substrate with a large Δn, the coupling length becomes long and miniaturization is not possible.

[0008] Patent Documents 4 and 5 disclose the configuration of an RGB multiplexer using an MMI (multimode interferometer), but in both cases the materials used are glass-based, and there is no disclosure at all about a configuration using a lithium niobate film. An MMI type optical multiplexer uses multiple waveguide ports on the optical input side to input multiple input signals, and on the optical output side, a single waveguide port is used for the output signal, with all input signals being multiplexed and output as an output signal.

[0009] At present, no optical multiplexer capable of handling high output has been developed.

[0010] The present invention aims to provide an optical multiplexer that can be connected to or integrated with an optical modulator using a lithium niobate film and can handle high output, as well as an optical multiplexing member, a visible light source module, and an optical engine that are equipped with the same. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides the following means.

[0012] A first aspect of the present invention is an optical multiplexer that multiplexes multiple laser beams of different wavelengths, and includes, for each laser beam, a multi-mode interference type input section with one input and multiple outputs as an optical input section for the laser beam, and further includes an optical output port from which the multiple laser beams can be multiplexed and output, a plurality of optical input side optical waveguides extending from each multi-mode interference type input section, an optical output side optical waveguide extending from the optical output port, and an optical multiplexing section to which the multiple optical input side optical waveguides and the optical output side optical waveguide are connected.

[0013] A second aspect of the present invention is an optical multiplexer according to the first aspect, further comprising a plurality of the optical output ports and a plurality of the optical output-side optical waveguides connected to the plurality of optical output ports, respectively.

[0014] A third aspect of the present invention is the optical multiplexer of the second aspect, wherein the interval between the most distant optical output ports among the plurality of optical output ports is 25 μm or less.

[0015] A fourth aspect of the present invention is the optical multiplexer according to any one of the first to third aspects, wherein the optical multiplexing section is a multi-mode interference type multiplexing section.

[0016] A fifth aspect of the present invention is an optical multiplexing member comprising a substrate made of a material other than lithium niobate, and an optical multiplexing function layer made of a lithium niobate film formed on a main surface of the substrate, in which any one of the optical multiplexers of the first to fourth aspects is formed in the optical multiplexing function layer.

[0017] A sixth aspect of the present invention is a visible light source module including the optical multiplexing member of the fifth aspect and a plurality of visible laser light sources that emit visible lasers multiplexed by the optical multiplexing member.

[0018] A seventh aspect of the present invention is an optical multiplexing member with an optical modulation function, which comprises a Mach-Zehnder type optical modulator in the optical multiplexing functional layer of the optical multiplexing member of the fifth aspect.

[0019] An eighth aspect of the present invention is a visible light source module including the optical multiplexing member with optical modulation function of the seventh aspect, and a plurality of visible laser light sources that emit visible lasers multiplexed by the optical multiplexing member with optical modulation function.

[0020] A ninth aspect of the present invention is an optical engine including the visible light source module of the sixth aspect, and a light scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image.

[0021] A tenth aspect of the present invention is an optical engine including the visible light source module of the eighth aspect, and a light scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image. Effect of the Invention

[0022] According to the present invention, it is possible to provide an optical multiplexer that can be connected to or integrated with an optical modulator using a lithium niobate film and that can handle high output. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a schematic plan view showing an optical multiplexer according to a first embodiment. [Diagram 2] FIG. 11 is a schematic plan view showing an optical multiplexer according to a second embodiment. [Diagram 3] FIG. 11 is a schematic plan view showing an optical multiplexer according to a third embodiment. [Figure 4] FIG. 13 is a schematic plan view showing an optical multiplexer according to a fourth embodiment. [Diagram 5] 2 is a schematic cross-sectional view taken along line XX' in FIG. 1 of an optical multiplexing member in which the components shown in FIG. 1 are formed in an optical multiplexing function layer made of lithium niobate. [Figure 6] 11 is a schematic plan view of a modified example of an optical multiplexing member according to an embodiment of the present invention. FIG. [Figure 7] 1 is a schematic plan view of a visible light source module according to a first embodiment. FIG. [Figure 8]FIG. 11 is a schematic plan view of a visible light source module according to a second embodiment. [Figure 9] FIG. 2 is a conceptual diagram for explaining an optical engine according to the present embodiment. [Figure 10] FIG. 13 is a diagram showing the relationship between the laser beam diameter and the distance Z from the laser emission surface corresponding to each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may show characteristic parts in an enlarged scale for the sake of convenience in order to make the characteristics easier to understand, and the dimensional ratios of each component may differ from the actual ones. The materials, dimensions, etc. exemplified in the following description are merely examples, and the present invention is not limited thereto, and may be appropriately modified and implemented within the scope of the effects of the present invention.

[0025] [Optical multiplexer (first embodiment)] 1 is a schematic plan view showing an optical multiplexer according to a first embodiment, in which L1, L2, and L3 conceptually show three laser beams.

[0026] The optical multiplexer 100 shown in FIG. 1 is an optical multiplexer that multiplexes three laser beams L1, L2, and L3 having different wavelengths, and is provided with one-input, two-output multimode interference type input units 60-1, 60-2, and 60-3 as optical input units for the laser beams for each laser beam. The optical multiplexer 100 further includes one optical output port 22o through which the three laser beams can be multiplexed and output, and each of the multimode interference type input units 60-1, 60-2, and 60-3 has a plurality of optical input ports 22a, 22b, 22c, 22d, 22e. 0-3, two of which extend from each of the optical input ports 21-11, 21-12, 21-21, 21-22, 21-31, and 21-32, in total; an optical output side optical waveguide 22 extending from the optical output port 22o; and an optical multiplexing section 50 to which the six optical input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, and 21-32 and the optical output side optical waveguide 22 are connected.

[0027] In FIG. 1, the X direction is perpendicular to the side surface 100A on which the optical input port is located, the Y direction is perpendicular to the X direction, and the Z direction is perpendicular to the plane formed by the X and Y directions.

[0028] The optical multiplexer 100 is configured to guide each laser beam to the optical multiplexing section 50 using two optical waveguides. That is, the laser beam L1 is received at the optical input port 61-1i of the multimode interference (MMI) type input section 60-1, and guided to the optical multiplexing section 50 using the two optical input side optical waveguides 21-11 and 21-12. The laser beam L2 is received at the optical input port 61-2i of the multimode interference (MMI) type input section 60-2, and guided to the optical multiplexing section 50 using the two optical input side optical waveguides 21-21 and 21-22. The laser beam L3 is received at the optical input port 61-3i of the multimode interference (MMI) type input section 60-3, and guided to the optical multiplexing section 50 using the two optical input side optical waveguides 21-31 and 21-32. In this way, by providing a plurality of optical input side optical waveguides that guide light to the optical multiplexing unit 50, the power density of the laser light guided by the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides. This is particularly an effective measure against damage to the optical waveguide of a high-output laser (e.g., laser light of 100 mW or more).

[0029] The dimensions of the optical input side optical waveguide and the optical output side optical waveguide can be, for example, 0.1 to 5 μm in width and 0.1 to 5 μm in height.

[0030] The optical multiplexer 100 is configured to be compatible with three laser beams having different wavelengths, but is not limited to three laser beams having different wavelengths, and may be configured for two laser beams having different wavelengths. The number of optical input ports and the number of optical input side optical waveguides connected to the optical input ports may be changed according to the number of laser beams. The input laser beams having different wavelengths can be visible light, but are not limited to visible light. A configuration may be used for visible laser beams and non-visible laser beams.

[0031] The optical multiplexer 100 has four sides 100A, 100B, 100C, and 100D, with three optical input ports provided on the first side 100A and an optical output port provided on the third side 100C, but the optical output port can also be provided on the second side 100B or the fourth side 100D.

[0032] The optical multiplexing unit 50 is a multi-mode interference (MMI) type multiplexer, but a directional coupler or a Y-shaped multiplexer may also be used. The optical multiplexing unit 50 is a 6-input 1-output type MMI type multiplexer, but is not limited to the 6-input 1-output type, and a multiple-input 1-output type or multiple-input multiple-output type MMI type multiplexer may also be used. By using a multimode interference (MMI) type multiplexer as the optical multiplexer 50, the coupling efficiency of multiplexing can be improved. In the optical multiplexer 100, the MMI type optical multiplexing section 50 has a one-stage configuration, but may have a two or more stages.

[0033] The optical input side optical waveguide and the optical output side optical waveguide connected to the optical multiplexing unit 50, which is an MMI type multiplexer, preferably have a tapered section that is wider as it approaches the input / output port of the optical multiplexing unit 50. The optical input side optical waveguide and the optical output side optical waveguide connected to the optical multiplexing unit 50 are set to propagate single mode (zeroth mode, fundamental mode), and the optical multiplexing unit 50 is set to propagate multimode (zeroth mode to higher mode). Therefore, when the light is input from the optical input side optical waveguide to the optical multiplexing unit 50 and output from the optical multiplexing unit 50 to the optical output side optical waveguide, a coupling loss occurs due to mode mismatch between the input single mode and multimode. On the other hand, if a tapered section is provided at the input / output port, the mode mismatch between the input single mode and multimode is alleviated, and the coupling loss is reduced. The wider the width of the tapered section, the more the mode mismatch is alleviated, and the greater the effect of reducing the coupling loss.

[0034] 1, the six optical input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, and 21-32 and the one optical output side optical waveguide 22 are configured to extend linearly in the x direction, but are not limited to such a configuration. They may have curved portions.

[0035] [Optical multiplexer (second embodiment)] 2 is a schematic plan view showing an optical multiplexer according to the second embodiment, in which the description of the same members as those in the first embodiment may be omitted.

[0036] The optical multiplexer 101 shown in FIG. 2 is an optical multiplexer that multiplexes three laser beams L1, L2, and L3 with different wavelengths, and is provided with one-input, two-output type multimode interference type input units 60-1, 60-2, and 60-3 as optical input units for the laser beams for each laser beam. In addition, the optical multiplexer 101 has two optical output ports 22-1o and 22-2o through which the three laser beams can be multiplexed and output, and ... and the optical input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, 21-32 extending from each of the optical input ports 21-11, 21-12, 21-21, 21-22, 21-31, 21-32; two optical output side optical waveguides 22-1, 22-2 extending from two optical output ports 22-1o, 22-2o, respectively; and an optical multiplexing section 51 to which the six optical input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, 21-32 and the two optical output side optical waveguides 22-1, 22-2 are connected.

[0037] The optical multiplexer 101 not only guides each laser beam to the optical multiplexing section 51 using two optical waveguides, but also has two optical output ports and outputs the multiplexed beam from the two optical output ports using two optical waveguides from the optical multiplexing section 51. That is, the laser beam L1 is received at the optical input port 61-1i of the multimode interference (MMI) type input section 60-1 and guided to the optical multiplexing section 50 using the two optical input side optical waveguides 21-11 and 21-12. The laser beam L2 is received at the optical input port 61-2i of the multimode interference (MMI) type input section 60-2 and guided to the optical multiplexing section 50 using the two optical input side optical waveguides 21-21 and 21-22. The laser light L3 is received at an optical input port 61-3i of a multimode interference (MMI) type input unit 60-3, and is guided to an optical multiplexing unit 51 using two optical input side optical waveguides 21-31 and 21-32. The light multiplexed in the optical multiplexing unit 51 is guided in an optical output side optical waveguide 22-1 and output from an optical output port 22-1o, and is also guided in an optical output side optical waveguide 22-2 and output from an optical output port 22-2o. In this way, by providing multiple optical input side optical waveguides that guide light to the optical multiplexing section 51, and further providing multiple optical output side optical waveguides that guide light from the optical multiplexing section 51, the power density of the laser light guided in the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides.

[0038] The distance do between the two optical output ports 22-1o and 22-2o is preferably 25 μm or less. This is because when the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams appear as one beam, producing a clear image. Here, the distance do is the distance between the centers of the optical output ports 22-1o and 22-2o, as shown in FIG. 1.

[0039] The distance do between the two optical output ports 22-1o and 22-2o is preferably 25 μm or less. This is because when the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams appear as one beam, producing a clear image. Here, the distance do is the distance between the centers of the optical output ports 22-1o and 22-2o, as shown in FIG. 2.

[0040] [Optical multiplexer (third embodiment)] 3 is a schematic plan view showing an optical multiplexer according to a third embodiment of the present invention, and the description of the same members as those in the above embodiments may be omitted.

[0041] The optical multiplexer 102 shown in FIG. 3 is an optical multiplexer that multiplexes three laser beams L1, L2, and L3 having different wavelengths, and includes one-input, three-output multimode interference type input units 60-11, 60-12, and 60-13 as optical input units for the laser beams, respectively, and further includes three optical output ports 22-11o, 22-12o, and 22-13o through which the three laser beams can be multiplexed and output, and a total of nine optical input side optical waveguides 21-111, 21-112 extending three by three from each of the multimode interference type input units 60-11, 60-12, and 60-13. , 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, 21-133, three optical output side optical waveguides 22-11, 22-12, 22-13 extending from the three optical output ports 22-11o, 22-12o, 22-13o, respectively, and an optical multiplexing section 52 to which the nine optical input side optical waveguides 21-111, 21-112, 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, 21-133 and the three optical output side optical waveguides 22-11, 22-12, 22-13 are connected.

[0042] The optical multiplexer 102 is configured to guide each laser beam to the optical multiplexing section 52 using three optical waveguides. That is, the laser beam L1 is received at the optical input port 61-11i of the multimode interference (MMI) type input section 60-11, and guided to the optical multiplexing section 52 using the three optical input side optical waveguides 21-111, 21-112, and 21-113. The laser beam L2 is received at the optical input port 61-12i of the multimode interference (MMI) type input section 60-12, and guided to the optical multiplexing section 52 using the three optical input side optical waveguides 21-121, 21-122, and 21-123. The laser light L3 is received at an optical input port 61-13i of a multimode interference (MMI) type input section 60-13, and is guided to the optical multiplexing section 52 using three optical input side optical waveguides 21-131, 21-132, and 21-133. Moreover, the optical multiplexer 102 has three optical output ports, and outputs multiplexed light from the three optical output ports using three optical waveguides from the optical multiplexing section 52. That is, the light multiplexed in the optical multiplexing section 52 is guided in the optical output side optical waveguide 22-11 and output from the optical output port 22-11o, guided in the optical output side optical waveguide 22-12 and output from the optical output port 22-12o, and guided in the optical output side optical waveguide 22-13 and output from the optical output port 22-13o. In this way, by providing multiple optical input side optical waveguides that guide light to the optical multiplexing section 52, and further providing multiple optical output side optical waveguides that guide light from the optical multiplexing section 52, the power density of the laser light guided in the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides.

[0043] Of the three optical output ports 22-11o, 22-12o, 22-13o, the interval do between the two optical output ports 22-11o, 22-12o at both ends is preferably 25 μm or less. The interval do1 between the two adjacent optical output ports 22-11o, 22-13o and the interval do1 between the two optical output ports 22-12o, 22-13o are preferably 10 μm or less. This is because when the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams appear as a single beam, producing a clear image.

[0044] The optical multiplexer 52 is a 9-input, 3-output MMI type multiplexer.

[0045] [Optical multiplexer (fourth embodiment)] 4 is a schematic plan view showing an optical multiplexer according to the fourth embodiment. Descriptions of members similar to those in the above embodiments may be omitted. The optical multiplexer according to the fourth embodiment is obtained by replacing the optical multiplexing section 52, which is a 9-input, 3-output MMI type multiplexer, of the optical multiplexer according to the fourth embodiment shown in FIG. 3 with an optical multiplexing section 53, which is a 9-input, 2-output MMI type multiplexer.

[0046] The optical multiplexer 103 shown in FIG. 4 is an optical multiplexer that multiplexes three laser beams L1, L2, and L3 having different wavelengths, and includes one-input, three-output multimode interference type input units 60-11, 60-12, and 60-13 as optical input units for the laser beams, respectively. The optical multiplexer 103 further includes three optical output ports 22-11o and 22-12o through which the three laser beams can be multiplexed and output, and a total of nine optical input side optical waveguides 21-111 and 21-112 extending three by three from each of the multimode interference type input units 60-11, 60-12, and 60-13. the two optical output side optical waveguides 22-11 and 22-12 extending from the two optical output ports 22-11o and 22-12o, respectively; and an optical multiplexing section 52 to which the nine optical input side optical waveguides 21-111, 21-112, 21-113, 21-121, 21-122, 21-123, 21-131, 21-132, and 21-133 and the two optical output side optical waveguides 22-11 and 22-12 are connected.

[0047] The optical multiplexer 103 is configured to guide each laser beam to the optical multiplexing section 53 using three optical waveguides. That is, the laser beam L1 is received at the optical input port 61-11i of the multimode interference (MMI) type input section 60-11, and guided to the optical multiplexing section 52 using the three optical input side optical waveguides 21-111, 21-112, and 21-113. The laser beam L2 is received at the optical input port 61-12i of the multimode interference (MMI) type input section 60-12, and guided to the optical multiplexing section 52 using the three optical input side optical waveguides 21-121, 21-122, and 21-123. The laser light L3 is received at an optical input port 61-13i of a multimode interference (MMI) type input section 60-13, and is guided to the optical multiplexing section 52 using three optical input side optical waveguides 21-131, 21-132, and 21-133. Moreover, the optical multiplexer 103 has two optical output ports, and is configured to output multiplexed light from three optical output ports using two optical waveguides from the optical multiplexing section 53. That is, the light multiplexed in the optical multiplexing section 52 is guided in the optical output side optical waveguide 22-11 and output from the optical output port 22-11o, and is also guided in the optical output side optical waveguide 22-12 and output from the optical output port 22-12o. In this way, by providing multiple optical input side optical waveguides that guide light to the optical multiplexing section 52, and further providing multiple optical output side optical waveguides that guide light from the optical multiplexing section 52, the power density of the laser light guided in the optical waveguides is dispersed, making it possible to suppress damage to the optical waveguides.

[0048] The distance do between the two optical output ports 22-11o and 22-12o is preferably 25 μm or less. This is because when the optical multiplexer 100 is applied to retinal projection type XR glasses, the beams appear as a single beam, producing a clear image.

[0049] [Optical multiplexing member] The optical multiplexing member according to the embodiment of the present invention includes a substrate made of a material different from lithium niobate, and an optical multiplexing functional layer made of a lithium niobate film formed on the main surface of the substrate, and the optical multiplexer according to the embodiment is formed in the optical multiplexing functional layer. In the components described below, components having the same functions as those in the above embodiment may be given the same reference numerals and their description may be omitted. In the optical multiplexing member 200 shown in FIG. 5, the optical multiplexer 100 shown in FIG. 1 is formed in the optical multiplexing functional layer.

[0050] FIG. 5 is a schematic cross-sectional view of the optical multiplexer 100 shown in FIG. 1 cut along the YZ plane (XX' in FIG. 1) of the optical multiplexing member 200 formed in an optical multiplexing functional layer made of lithium niobate. The optical multiplexing member 200 shown in FIG. 5 includes a substrate 10 made of a material different from lithium niobate, and an optical multiplexing functional layer 20 made of lithium niobate and formed on a main surface of the substrate 10. The multimode interference type input section, the optical output port, the optical multiplexing section, the optical input side optical waveguide, and the optical output side optical waveguide are formed in an optical multiplexing functional layer 20 .

[0051] In the optical multiplexing member 200, when the refractive index difference between the waveguide core film and the waveguide clad film is Δn, if the waveguide core film is made of lithium niobate, Δn can be designed to be a larger value than when using materials such as glass, and the radius of curvature of the optical waveguide can be made smaller. Furthermore, by using a multimode interference type optical multiplexing section, an increase in coupling length can be prevented compared to when a directional coupler is used, thereby achieving both improved design freedom and miniaturization.

[0052] The optical multiplexing functional layer 20 comprises a waveguide core film 24 made of a lithium niobate film in which the optical input port, the optical output port, the optical multiplexing section, the optical input side optical waveguide, and the output side optical waveguide are formed, and a waveguide clad (buffer) film 25 formed on the waveguide core film 24 so as to cover these. Hereinafter, the reference symbol 24 may also be used to refer to the lithium niobate film.

[0053] Examples of the substrate 10 include a sapphire substrate, a Si substrate, and a thermally oxidized silicon substrate. Since the optical multiplexing functional layer 20 is made of a lithium niobate (LiNbO3) film, there is no particular limitation as long as the refractive index is lower than that of the lithium niobate film, but a sapphire single crystal substrate or a silicon single crystal substrate is preferred as a substrate on which the single crystal lithium niobate film can be formed as an epitaxial film. The crystal orientation of the single crystal substrate is not particularly limited, but for example, since a c-axis oriented lithium niobate film has three-fold symmetry, it is desirable that the underlying single crystal substrate also has the same symmetry, and in the case of a sapphire single crystal substrate, a c-plane substrate is preferred, and in the case of a silicon single crystal substrate, a (111) plane substrate is preferred.

[0054] The lithium niobate film is, for example, a c-axis oriented lithium niobate film. The lithium niobate film is, for example, an epitaxial film epitaxially grown on the substrate 10. The epitaxial film is a single crystal film whose crystal orientation is aligned by the underlying substrate. The epitaxial film is a film having a single crystal orientation in the z direction and the xy in-plane direction, and the crystals are aligned in the x-axis, y-axis, and z-axis directions. Whether the film formed on the substrate 10 is an epitaxial film can be proved by, for example, checking the peak intensity and pole at the orientation position in 2θ-θ X-ray diffraction.

[0055] Specifically, when measured by 2θ-θX-ray diffraction, all peak intensities other than the target plane are 10% or less, preferably 5% or less, of the maximum peak intensity of the target plane. For example, when the lithium niobate film is a c-axis oriented epitaxial film, the peak intensities other than the (00L) plane are 10% or less, preferably 5% or less, of the maximum peak intensity of the (00L) plane. Here, (00L) is a general designation for equivalent planes such as (001) and (002).

[0056] Moreover, the conditions for confirming the peak intensity at the orientation position described above only indicate the orientation in one direction. Therefore, even if the above conditions are obtained, if the crystal orientation is not uniform in the plane, the intensity of the X-rays will not increase at a specific angle position, and no poles will be observed. For example, in the case of a lithium niobate film, since LiNbO3 has a trigonal crystal structure, there are three poles of LiNbO3 (014) in the single crystal. In the case of lithium niobate, it is known that the epitaxial growth occurs in a so-called twin state in which crystals rotated 180° around the c-axis are symmetrically bonded. In this case, the three poles are symmetrically bonded to two, so there are six poles. In addition, when a lithium niobate film is formed on a silicon single crystal substrate with a (100) plane, the substrate is four-fold symmetric, so 4x3=12 poles are observed. In this disclosure, a lithium niobate film epitaxially grown in a twin state is also included in the epitaxial film.

[0057] The composition of lithium niobate is LixNbAyOz. A is an element other than Li, Nb, and O. x is 0.5 or more and 1.2 or less, and preferably 0.9 or more and 1.05 or less. y is 0 or more and 0.5 or less. z is 1.5 or more and 4.0 or less, and preferably 2.5 or more and 3.5 or less. The element A is, for example, K, Na, Rb, Cs, Be, Mg, Ca, Sr, Ba, Ti, Zr, Hf, V, Cr, Mo, W, Fe, Co, Ni, Zn, Sc, and Ce, and two or more of these elements may be combined. Furthermore, the lithium niobate film may be a lithium niobate single crystal thin film bonded onto a substrate.

[0058] The thickness of the lithium niobate film is, for example, 2 μm or less. The thickness of the lithium niobate film refers to the thickness of the portion other than the ridge. The thickness of the lithium niobate film can be optimally designed according to the wavelength and ridge shape to be used.

[0059] The waveguide is a ridge protruding from the first surface 24A of the lithium niobate film 24. The first surface 24A is the upper surface of the portion (slab layer) of the lithium niobate film 24 other than the ridge. 5, the cross-sectional shape of the cross-sectional shape fixed portion of the light input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, and 21-32 is rectangular, but any shape capable of guiding light may be used, for example, a trapezoid, a triangle, a semicircle, etc. The width Wa of the three ridges in the y direction is preferably 0.2 μm or more and 5.0 μm or less, and the height of the three ridges (protruding height Ha from the first surface 24A) is preferably, for example, 0.1 μm or more and 1.0 μm or less. The same applies to the other optical waveguides.

[0060] By making the size of the light input side optical waveguides 21-11, 21-12, 21-21, 21-22, 21-31, 21-32 and other optical waveguides shown in FIG. 1 approximately the wavelength of the laser light, propagation in a single mode can be achieved.

[0061] FIG. 6 is a schematic plan view of a modified example of the optical multiplexing member according to the embodiment of the present invention. The optical multiplexing member 300 shown in Figure 6 is an optical multiplexing member with optical modulation function, comprising a substrate 10 (see Figure 5) made of a material other than lithium niobate, and an optical multiplexing function layer 20 made of a lithium niobate film formed on the main surface of the substrate 10, in which the optical multiplexer according to the above embodiment and a Mach-Zehnder type optical modulator are formed.

[0062] An optical multiplexing member 300 with an optical modulation function shown in FIG. 6 illustrates a case where the optical multiplexer 100 shown in FIG. 1 is included in the optical multiplexers according to the above embodiments. The optical multiplexing member 300 with an optical modulation function includes an optical multiplexer 100 and a Mach-Zehnder type optical modulator 40 in an optical multiplexing function layer 20 .

[0063] The Mach-Zehnder type optical modulator 40 includes six Mach-Zehnder type optical waveguides 40-1, 40-2, 40-3, 40-4, 40-5, and 40-6. The Mach-Zehnder type optical waveguide 40-1 is provided between the optical input side optical waveguide 21-11 and the optical multiplexing section 50. The Mach-Zehnder type optical waveguide 40-2 is provided between the optical input side optical waveguide 21-12 and the optical multiplexing section 50. The Mach-Zehnder type optical waveguide 40-3 is provided between the optical input side optical waveguide 21-21 and the optical multiplexing section 50. The Mach-Zehnder type optical waveguide 40-2 is provided between the optical input side optical waveguide 21-22 and the optical multiplexing section 50. The Mach-Zehnder type optical waveguide 40-5 is provided between the optical input side optical waveguide 21-31 and the optical multiplexing section 50. The Mach-Zehnder type optical waveguide 40-6 is provided between the optical input side optical waveguide 21-32 and the optical multiplexing section 50.

[0064] A known Mach-Zehnder type optical modulator or an optical waveguide can be used as the Mach-Zehnder type optical modulator 40, which splits (demultiplexes) an optical beam with a uniform wavelength and phase into two paired beams, gives each beam a different phase, and then combines (combines) them. The intensity of the combined optical beam changes depending on the difference in phase.

[0065] 6 each include an optical waveguide 41, an optical waveguide 42, an input path 43, an output path 44, a branching portion 45, and a coupling portion 46. In the figure, only the Mach-Zehnder optical waveguide 40-1 is shown with reference symbols for each component. The output paths 44 of the Mach-Zehnder type optical waveguides 40-1, 40-2, 40-3, 40-4, 40-5, and 40-6 are optically connected to an optical multiplexing section 50. The first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 6 are configured to extend linearly in the x direction except for the vicinity of the branching portion 45 and the vicinity of the coupling portion 46, but are not limited to such a configuration. The lengths of the first optical waveguide 41 and the second optical waveguide 42 shown in FIG. 6 are approximately the same. The branching portion 45 is between the input path 43 and the first optical waveguide 41 and the second optical waveguide 42. The input path 43 is connected to the first optical waveguide 41 and the second optical waveguide 42 via the branching portion 45. The coupling portion 46 is between the first optical waveguide 41 and the second optical waveguide 42 and the output path 44. The first optical waveguide 41 and the second optical waveguide 42 are connected to the output path 44 via the coupling portion 46.

[0066] The electrodes 29 and 26 are electrodes that apply a modulation voltage to each of the Mach-Zehnder optical waveguides 40-1, 40-2, 40-3, 40-4, 40-5, and 40-6 (hereinafter, sometimes simply referred to as "each Mach-Zehnder optical waveguide 40"). The electrode 29 is an example of a first electrode, and the electrode 26 is an example of a second electrode. One end of the electrode 29 is connected to a power source 131, and the other end is connected to a termination resistor 132. One end of the electrode 26 is connected to the power source 131, and the other end is connected to the termination resistor 132. The power source 131 is a part of a drive circuit that applies a modulation voltage to each of the Mach-Zehnder optical waveguides 40. For the sake of simplicity, the electrodes 29 and 26 are drawn only on the part of the Mach-Zehnder optical waveguide 40-6.

[0067] The electrodes 27 and 28 are electrodes that apply a DC bias voltage to each Mach-Zehnder type optical waveguide 40. One end of the electrode 27 and one end of the electrode 28 are connected to a power source 133. The power source 133 is a part of a DC bias application circuit that applies a DC bias voltage to each Mach-Zehnder type optical waveguide 40. When a DC bias voltage is superimposed on the electrodes 29, 26, the electrodes 27, 28 do not need to be provided. Also, ground electrodes may be provided around the electrodes 29, 26, 27, 28.

[0068] [Visible Light Source Module (First Embodiment)] The visible light source module according to the first embodiment includes the optical multiplexing member according to the above embodiments, and a plurality of visible light laser light sources that emit visible light multiplexed in the optical multiplexing member. 7 is a schematic plan view of a visible light source module according to this embodiment, which illustrates an example of a visible light source module including the optical multiplexing member 200 illustrated in FIG.

[0069] 7 includes an optical multiplexing member 200 having an optical multiplexing section 50, and three visible laser light sources 30 (30-1, 30-2, 30-3) that emit visible light multiplexed by the optical multiplexing member 200. The optical multiplexing member 200 includes a substrate 10 (see FIG. 5) made of a material different from lithium niobate, and an optical multiplexing functional layer 20 (see FIG. 5) made of lithium niobate and formed on the main surface of the substrate 10, and has a side surface 200A as a light incident surface. Regarding the components shown in FIG. 7, components having the same functions as those described above are denoted by the same reference numerals, and the description thereof may be omitted.

[0070] Various laser elements can be used as the visible light laser light source 30. For example, commercially available laser diodes (LDs) for red light, green light, blue light, etc. can be used. For red light, light with a peak wavelength of 600 nm or more and 750 nm or less can be used, for green light, light with a peak wavelength of 500 nm or more and 600 nm or less can be used, and for blue light, light with a peak wavelength of 380 nm or more and 500 nm or less can be used. In the visible light source module 1000, for example, the visible light laser light sources 30-1, 30-2, and 30-3 are an LD that emits red light, an LD that emits green light, and an LD that emits blue light, respectively. The LDs 30-1, 30-2, and 30-3 are disposed at intervals from each other in a direction substantially perpendicular to the emission direction of the light emitted from each LD, and are provided on the upper surface of the subcarrier 120.

[0071] In the visible light source module 1000, the number of visible light laser light sources is 3, but the number is not limited to 3 as long as there is more than one, and may be 2, 4 or more. The multiple visible light laser light sources may all emit light with different wavelengths, or there may be visible light laser light sources that emit light with the same wavelength. In addition, light other than red (R), green (G), and blue (B) may be used as the emitted light, and the mounting order of red (R), green (G), and blue (B) explained using the drawings does not have to be in this order and can be changed as appropriate.

[0072] The LD 30 can be mounted as a bare chip on the subcarrier 120. The subcarrier 120 is made of, for example, aluminum nitride (AlN) or aluminum oxide (Al 2 O 3 ), silicon (Si), etc.

[0073] The subcarrier 120 can be directly bonded to the substrate 10 via a metal bonding layer. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. By configuring the subcarrier 120 and the substrate 10 to be bonded via a metal bonding layer, the relative positions of the subcarrier 120 and the substrate 10 can be adjusted during manufacture to align the optical axis position of the laser light so that the optical axes of each visible light laser coincide with the axes of the multimode interference type input section 60-1, multimode interference type input section 60-2, and multimode interference type input section 60-3, respectively (active alignment).

[0074] In the visible light source module 1000, the optical input port (optical input port) 61-1i of the multimode interference type input section 60-1, the optical input port (optical input port) 61-2i of the multimode interference type input section 60-2, and the optical input port (optical input port) 61-3i of the multimode interference (MMI) type input section 60-3 face the exit ports of the LDs 30 (30-1, 30-2, 30-3), and are positioned so that light emitted from the exit surface of each LD 30 can enter the optical input ports 61-1i, 61-2i, and 61-3i. With this configuration and arrangement, the red light, green light, and blue light emitted from the LDs 30-1, 30-2, and 30-3 can enter the three multimode interference type input sections 60-1, 60-2, and 60-3 of the optical multiplexing section 50.

[0075] In the visible light source module 1000, the light exit surface 31 of the LD 30 and the light entrance surface 200A of the light combining member 200 are disposed at a predetermined interval. The light entrance surface 200A faces the light exit surface 31, and there is a gap S between the light exit surface 31 and the light entrance surface 200A in the x direction. Since the visible light source module 1000 is exposed to the air, the gap S is filled with air. Since the gap S is filled with the same gas (air), it is easy to make each color light emitted from the LD 30 enter the entrance path while satisfying a predetermined coupling efficiency. When the visible light source module 1000 is used for AR glasses or VR glasses, the size of the gap (spacing) S in the x direction is, for example, larger than 0 μm and 5 μm or less, taking into account the amount of light required for the AR glasses or VR glasses.

[0076] [Visible Light Source Module (Second Embodiment)] FIG. 8 is a schematic plan view of the visible light source module according to the second embodiment. The visible light source module 2000 shown in Fig. 8 includes the optical multiplexing member 300 with optical modulation function shown in Fig. 6, and a plurality of visible light laser light sources 30 (30-1, 30-2, 30-3) that emit visible light that is multiplexed by the optical multiplexing member 300 with optical modulation function. The optical multiplexing member 300 includes a substrate 10 (see Fig. 5) made of a material different from lithium niobate, an optical multiplexing function layer 20 (see Fig. 5) made of lithium niobate and formed on the main surface of the substrate 10, and has a side surface 300A. Regarding the components shown in FIG. 8, components having the same functions as those described above are given the same reference numerals, and the description thereof may be omitted.

[0077] The visible light source module 2000 has six Mach-Zehnder optical waveguides 40-1, 40-2, 40-3, 40-4, 40-5, and 40-6, which is the same number as the number of visible laser light sources 30-1, 30-2, and 30-3. The visible laser light sources 30-1, 30-2, and 30-3, the optical input port 61-1i of the multimode interference type input unit 60-1, the optical input port 61-2i of the multimode interference type input unit 60-2, and the optical input port 61-3i of the multimode interference (MMI) type input unit 60-3 (see FIG. 6) are positioned so that light emitted from the visible laser light sources enters the corresponding Mach-Zehnder optical waveguides.

[0078] The subcarrier 120 on which the visible laser light sources 30-1, 30-2, and 30-3 are mounted and the substrate 10 on which the optical multiplexing function layer 20 having the optical multiplexing member 300 with optical modulation function is formed can be directly bonded via a metal bonding layer. This configuration makes it possible to further reduce the size by eliminating spatial coupling or fiber coupling. Furthermore, during manufacturing, the relative positions of the subcarrier 120 and the substrate 10 can be adjusted to align the optical axis position of the laser light (active alignment).

[0079] The size of the optical multiplexing functional layer 20 is, for example, 100 mm 2 or less. If the size of the optical multiplexing functional layer 20 is 100 mm 2 or less, it is suitable for use in xR glasses such as AR glasses and VR glasses.

[0080] The optical multiplexing function layer 20 can be manufactured by a known method, for example, by using semiconductor processes such as epitaxial growth, photolithography, etching, vapor phase growth, and metallization.

[0081] When the visible light source module according to the present invention is applied to xR glasses such as AR glasses or VR glasses, the width of the first multimode interference type optical multiplexing section and the second multimode interference type optical multiplexing section constituting the optical multiplexer is preferably, for example, about 1 to 1000 μm, and the length thereof is preferably, for example, about 10 to 10000 μm.

[0082] For example, in a retinal projection display, in order to display an image in a desired color, it is necessary to independently modulate the intensity of each of the three colors of RGB that express visible light at high speed. If such modulation is performed only with a visible light laser light source (current modulation), the load on the IC that controls the modulation will be large, but it is possible to use modulation (voltage modulation) by a Mach-Zehnder type optical modulator 40 (optical multiplexing member 300 with optical modulation function) in combination. In this case, rough adjustment may be performed with a current (visible light laser light source) and fine adjustment with a voltage (Mach-Zehnder type optical modulator 40), or rough adjustment may be performed with a voltage (Mach-Zehnder type optical modulator 40) and fine adjustment with a current (visible light laser light source). Since fine adjustment with voltage has better responsiveness, the former is adopted when responsiveness is important, and since fine adjustment with current requires a lower current and thus reduces power consumption, it is preferable to adopt the latter when reducing power consumption is important.

[0083] [Optical engine] In this specification, an optical engine refers to a device that includes multiple light sources, an optical system including a multiplexing section that combines multiple light beams emitted from the multiple light sources into a single beam of light, an optical scanning mirror that reflects the light emitted from the optical system at a different angle so as to display an image, and a control element that controls the optical scanning mirror.

[0084] 9 is a conceptual diagram for explaining an optical engine 5001 according to this embodiment. The diagram shows a state in which the optical engine 5001 is mounted on a frame 10010 of glasses 10000. Symbol L denotes image display light.

[0085] The optical engine 5001 includes a visible light source module 1001 and a light scanning mirror 3001. As the visible light source module 1001 included in the optical engine 5001, the visible light source module according to the above-described embodiment is used.

[0086] Laser light emitted from a visible light source module 1001 attached to the eyeglass frame is reflected and scanned by a light scanning mirror, enters the human eye, and an image (video) is projected directly onto the retina.

[0087] The optical scanning mirror 3001 is, for example, a MEMS mirror. In order to project a 2D image, it is preferable that the optical scanning mirror 3001 is a two-axis MEMS mirror that vibrates so as to reflect the laser light by changing the angle in the horizontal direction (X direction) and the vertical direction (Y direction).

[0088] The optical engine 5001 has a collimator lens 2001a, a slit 2001b, and an ND filter 2001c as an optical system that optically processes the laser light emitted from the visible light source module 1001. This optical system is just an example, and other configurations may be used.

[0089] The optical engine 5001 includes a laser driver 1100, an optical scanning mirror driver 1200, and a video controller 1300 that controls these drivers. EXAMPLES

[0090] The present invention will be described in more detail below using examples, but the present invention is not limited to the examples shown below.

[0091] In the first embodiment, an optical multiplexing member having the configuration shown in FIG. 2 is used. In Examples 2, 4 and 5, an optical multiplexing member having the configuration shown in FIG. 4 is used. The third embodiment is an optical multiplexing member having the configuration shown in FIG. In the sixth embodiment, an optical multiplexing member having the configuration shown in FIG. 1 is used. Comparative Example 1 uses an optical multiplexing member in which the optical multiplexing section 50 in the configuration shown in FIG. 1 is replaced with a 3-input 1-output type MMI type optical multiplexer.

[0092] In Table 1, the shape of the input port indicates whether it is an MMI type input part or not. The laser coupling efficiency is the result of a simulation. Fimmwave (Photon Design) was used as the simulation software. The laser coupling efficiency indicates the ratio of the power of the laser light propagated to the optical input side optical waveguide. The interval between the output ports corresponds to the distance indicated by the symbol do in Figures 2 to 4. The deterioration of the optical waveguide was judged by the shape of the laser beam output from the optical output port. When the shape of the laser beam input to the optical input side optical waveguide and the shape of the laser beam output from the optical output port are in a similar relationship, it was judged that there was no deterioration, and when there was no similar relationship and there was a change in the shape, it was judged that there was deterioration.

[0093] [Table 1]

[0094] FIG. 10 is a diagram for explaining the relationship between the laser beam diameter corresponding to each embodiment and the distance Z from the laser emission surface (corresponding to the gap S in FIGS. 9 and 10) in the case of a Gaussian beam. The laser beam diameter is defined by the following equation (2).

[0095]

number

[0096] In equations (1) and (2), ω 0is the beam waist (the value at which the beam diameter is minimized by diffraction), Z is the distance from the laser light source (corresponding to the gap S in Figures 7 and 8) (see Figure 10), and λ is the wavelength of the laser light. Table 2 shows the beam waist ω 0 The figures show the laser beam diameters [μm] of the RGB laser lights when the distance Z from the laser emission surface is 1 μm, 2.5 μm, and 4 μm, respectively, when the laser diameter is 0.2 μm. Z=1 μm corresponds to Comparative Example 1, Z=2.5 μm corresponds to Examples 1 and 6, and Z=4 μm corresponds to Examples 2 to 5.

[0097] [Table 2]

[0098] In the first, fourth to sixth embodiments, the laser light incident from each laser light source to the optical multiplexer is guided to the optical multiplexer by two optical input-side optical waveguides. Therefore, compared to the comparative example in which the laser light incident from each laser light source to the optical multiplexer is guided to the optical multiplexer by one optical input-side optical waveguide, the first, fourth to sixth embodiments distribute the power density of the laser light to two optical input-side optical waveguides while maintaining the same coupling efficiency with the laser, and therefore, it is possible to suppress deterioration of the optical input-side optical waveguide compared to the comparative example. Therefore, the first, fourth to sixth embodiments are also suitable as optical multiplexers for high-power lasers. Moreover, in Examples 2 and 3, each laser light incident from each laser light source to the optical multiplexer is guided to the optical multiplexing section through three optical input side optical waveguides. Therefore, compared to the comparative example in which each laser light incident from each laser light source to the optical multiplexer is guided to the optical multiplexing section through one optical input side optical waveguide, Examples 2 and 3 distribute the power density of the laser light to three optical input side optical waveguides while maintaining the same coupling efficiency with the laser, making it possible to suppress deterioration of the optical input side optical waveguide compared to the comparative example. Therefore, Examples 2 and 3 are also suitable as optical multiplexers for high-power lasers.

[0099] Moreover, Examples 1, 2, 4, and 5 are configured to have two optical output ports, and output light by guiding the light from the optical multiplexing unit to each optical output port through two optical output-side optical waveguides. Therefore, compared to the comparative example in which there is one optical output port and one optical output-side optical waveguide guides the light to the optical output port, Examples 1, 2, 4, and 5 distribute the power density of the laser light to two optical output-side optical waveguides to output light, making it possible to suppress deterioration of the optical input-side optical waveguide compared to the comparative example. Therefore, Examples 2 and 3 are also suitable as optical multiplexers for high-power lasers. Moreover, the third embodiment has three optical output ports, and outputs light by guiding the light from the optical multiplexing unit to each optical output port through three optical output-side optical waveguides. Therefore, compared to the comparative example having one optical output port and guiding the light to the optical output port through one optical output-side optical waveguide, the third embodiment distributes the power density of the laser light to three optical output-side optical waveguides to output light, and therefore it is possible to suppress deterioration of the optical input-side optical waveguide compared to the comparative example. Therefore, the third embodiment is also suitable as an optical multiplexer for high-power lasers. [Explanation of symbols]

[0100] 10 Substrate 20 Optical multiplexing functional layer 30 Visible light laser source 40 Mach-Zehnder type optical modulator 50, 51, 52 Optical multiplexing section 60-1, 60-2, 60-3 Multimode interference type input section 100, 101, 102 optical multiplexer 200, 300 Optical multiplexing member 1000 2000 Visible light source module

Claims

1. An optical multiplexer that multiplexes a plurality of laser beams having different wavelengths, For each laser beam, a multi-mode interference type input section having one input and multiple outputs is provided as an optical input section for the laser beam, an optical output port capable of outputting the multiple laser beams after being multiplexed; a plurality of optical input side optical waveguides extending from each multimode interference type input section; an optical output side optical waveguide extending from the optical output port; an optical multiplexing section to which the plurality of optical input side optical waveguides and the optical output side optical waveguide are connected.

2. 2. The optical multiplexer according to claim 1, comprising a plurality of said optical output ports, and a plurality of said optical output side optical waveguides connected to each of said plurality of optical output ports.

3. 3. The optical multiplexer according to claim 2, wherein the distance between the most distant optical output ports among said plurality of optical output ports is 25 [mu]m or less.

4. 2. The optical multiplexer according to claim 1, wherein the optical multiplexer is a multimode interference type multiplexer.

5. a substrate made of a material different from lithium niobate; a light-multiplexing functional layer formed on a main surface of the substrate and made of a lithium niobate film; 5. An optical multiplexing member comprising an optical multiplexer according to claim 1 formed in an optical multiplexing functional layer.

6. A visible light source module comprising: the optical multiplexer according to claim 5; and a plurality of visible laser light sources that emit visible laser beams multiplexed by the optical multiplexer.

7. 6. An optical multiplexing member with an optical modulation function, comprising a Mach-Zehnder type optical modulator in the optical multiplexing functional layer of the optical multiplexing member according to claim 5.

8. 8. A visible light source module comprising: the optical multiplexer with optical modulation function according to claim 7; and a plurality of visible light laser light sources that emit visible light lasers multiplexed by the optical multiplexer with optical modulation function.

9. A visible light source module according to claim 6; an optical scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image;

10. A visible light source module according to claim 8; an optical scanning mirror that reflects the light emitted from the visible light source module at a different angle so as to display an image;

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