Optical axis adjustment device and optical communication device

Abstract

To achieve the control of a light beam in a travel direction with a wedge prism with high accuracy.SOLUTION: An optical axis adjustment device (1) includes: a first wedge prism (31) and a second wedge prism (32) rotatably arranged around a rotation axis (CA) as an axis; voice coil motors for rotating the respective prisms; and a CPU (21) that controls energization of the voice coil motors according to rotation angles of the wedge prisms corresponding to a specific direction of emitted light.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical axis adjustment device and an optical communication device. [Background technology]

[0002] In optical communications, it is preferable to reduce the number of intermediate transmission devices required to transmit a beam to its destination in order to increase efficiency. This requires higher accuracy in transmission and reception. In optical communications, lenses are generally used to diffuse and focus a light beam during transmission and reception. To increase the accuracy of focusing, a known technique is to transmit a light beam LB by controlling the direction of travel of the light beam LB emitted from a light-emitting element 110 toward a lens 130 using a wedge prism pair 140, as shown in FIG. 20 . The control of the direction of travel of the light beam by the wedge prism is achieved by rotating the wedge prism. A known technique for rotating a wedge prism is to use a hollow motor as a driving source for rotation (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2016 / 024340 Summary of the Invention [Problem to be solved by the invention]

[0004] Due to its structure, hollow motors are prone to generating micro-vibrations. Therefore, when a hollow motor is used as a drive source to rotate a wedge prism, the wedge prism may not be able to fully control the direction of travel of the light beam with high precision. In particular, in optical communications, significant vibrations in the thrust direction can easily cause a significant degradation in performance. Thus, there is still room for improvement in the control of the direction of travel of a light beam using a wedge prism in optical communications, with the aim of achieving even more precise control.

[0005] An object of one aspect of the present invention is to realize highly accurate control of the traveling direction of a light beam using a wedge prism. [Means for solving the problem]

[0006] In order to solve the above problem, an optical axis adjustment device according to one aspect of the present invention includes a wedge prism that is arranged to be rotatable around a specific axis, a voice coil motor for rotating the wedge prism, and a control device for controlling the flow of current to the voice coil motor in accordance with the rotation angle of the wedge prism that corresponds to a specific orientation of the optical axis of light emitted from the wedge prism.

[0007] In order to solve the above-mentioned problems, an optical communication device according to an aspect of the present invention includes the optical axis adjusting device of the present invention. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to control the direction of travel of a light beam with high precision using a wedge prism. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram schematically illustrating a configuration of an optical axis adjusting device according to an embodiment of the present invention. [Figure 2] 1 is a diagram illustrating a structure of an optical axis adjusting device according to an embodiment of the present invention in a thrust direction; [Figure 3] FIG. 2 is a plan view schematically showing a coil according to an embodiment of the present invention. [Figure 4] FIG. 10 is a diagram schematically illustrating the arrangement of coils arranged corresponding to a wedge prism in one embodiment of the present invention. [Figure 5] FIG. 2 is a diagram illustrating an example of an electric circuit including a coil according to an embodiment of the present invention. [Figure 6] 3A and 3B are diagrams schematically showing grooves formed on a substrate in an embodiment of the present invention. [Figure 7] FIG. 2 is a diagram illustrating a schematic diagram of the positional relationship between a magnet and a coil in one embodiment of the present invention. [Figure 8] 10A and 10B are diagrams for explaining the generation of thrust force during rotation in an embodiment of the present invention. [Figure 9] 10A and 10B are diagrams for explaining the direction of thrust force of rotation in the embodiment of the present invention. [Figure 10] 5A and 5B are diagrams for explaining control of current supply to a coil in the embodiment of the present invention. [Figure 11] 5A and 5B are diagrams illustrating a relationship between a detection value of a Hall element and a rotation angle of a wedge prism in an embodiment of the present invention. [Figure 12] 4A and 4B are diagrams illustrating a relationship between the rotation angle of a wedge prism and the refraction angle of a light beam emitted from the wedge prism in an embodiment of the present invention. [Figure 13] 10A and 10B are diagrams for explaining adjustment of the direction of the optical axis of a light beam by a pair of wedge prisms in an embodiment of the present invention. [Figure 14] 10A and 10B are diagrams for explaining adjustment of the direction of the optical axis of a light beam by two pairs of wedge prisms in an embodiment of the present invention. [Figure 15] 1 is a diagram schematically illustrating a configuration of an optical communication device according to an embodiment of the present invention. [Figure 16] FIG. 1 is a diagram schematically illustrating an example of the configuration of a conventional optical communication device. [Figure 17] 10A and 10B are diagrams illustrating a first example of coil arrangement when the center of gravity of the rotating body is shifted from the rotation axis in the embodiment of the present invention. [Figure 18] 10A and 10B are diagrams illustrating a second example of coil arrangement when the center of gravity of the rotating body is shifted from the rotation axis in the embodiment of the present invention. [Figure 19] FIG. 10 is a diagram schematically illustrating another example of an electric circuit between a coil and a power source according to an embodiment of the present invention. [Figure 20] FIG. 10 is a diagram schematically illustrating another example of the configuration of a conventional optical communication device. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Optical axis adjustment device] [composition] An embodiment of the present invention will be described in detail below. Fig. 1 is a diagram schematically showing the configuration of an optical axis adjustment device according to an embodiment of the present invention. Fig. 2 is a diagram schematically showing the structure of an optical axis adjustment device according to an embodiment of the present invention in order to explain the structure in the thrust direction of the optical axis adjustment device. As shown in Figs. 1 and 2, the optical axis adjustment device 1 has a substrate 2, a wedge prism pair 3 supported on one main surface of the substrate 2, and a casing 4 on the substrate 2 that houses the wedge prism pair 3.

[0011] The substrate 2 is a plate material having an annular shape in a plan view. The substrate 2 has a circular hole in the center of its planar shape. The axis that passes through the center of this hole and is perpendicular to one main surface of the substrate is defined as the rotation axis CA.

[0012] The substrate 2 has a CPU 21, a first coil 22, a second coil 23, a first hall element 24, and a second hall element 25. The CPU 21 controls the supply of electricity from a power supply (not shown) to the first coil 22 and the second coil 23. The first coil 22 and the second coil 23 are disposed on one main surface of the substrate 2.

[0013] Fig. 3 is a plan view schematically showing a coil according to one embodiment of the present invention. As shown in Fig. 3, both first coil 22 and second coil 23 are formed of a conductor wound in a generally fan-shaped configuration when viewed in plan. θ represents the angle formed by the direction along the central axis of the generally fan-shaped configuration of first coil 22 and second coil 23 and the linear outer periphery of the generally fan-shaped configuration. Thus, both first coil 22 and second coil 23 have a fan-shaped configuration that widens outward from the rotation axis when viewed in plan.

[0014] A plurality of first coils 22 and a plurality of second coils 23 are arranged, and each of the first coils 22 and the second coils 23 is arranged at a rotationally symmetrical position when viewed from above. The first coils 22 and the second coils 23 are arranged in the same manner.

[0015] Fig. 4 is a diagram schematically illustrating the arrangement of coils arranged corresponding to wedge prisms in one embodiment of the present invention. For example, as shown in Fig. 4, first coil 22 is arranged at a position of three-fold rotational symmetry with rotation axis CA as the center of rotation in a plan view. Second coil 23 is also arranged at a position of three-fold rotational symmetry similar to first coil 22. In Fig. 4, reference numeral 31 denotes a first wedge prism, which will be described later, and reference numeral 35 denotes a first frame, which will be described later.

[0016] When the first coil 22 and the second coil 23 are arranged on the same plane, the first coil 22 and the second coil 23 are arranged so that their positions are shifted from each other when viewed in a plane. For example, when the first coil 22 and the second coil 23 are arranged at positions with three-fold rotational symmetry, the first coil 22 and the second coil 23 are arranged in a positional relationship where they are rotated 60° from each other.

[0017] The first coil 22 and the second coil 23 are each connected to a power supply. Figure 5 is a diagram schematically illustrating an example of an electric circuit including coils in one embodiment of the present invention. As shown in Figure 5, the three first coils 22 are connected in series to the power supply, and the three second coils 23 are connected in series to the power supply.

[0018] 6 is a diagram schematically showing grooves formed on a substrate in an embodiment of the present invention. As shown in FIG. 2, substrate 2 has ball receiving portion 29 on one main surface thereof. Ball receiving portion 29 is a protrusion portion having a circular arc shape in plan view. A groove 26 is formed on the top of ball receiving portion 29 along the longitudinal direction of ball receiving portion 29.

[0019] As shown in FIG. 6, the recessed ribs 26 have a planar shape that is aligned with the circumferential direction of the substrate 2 (the long axis direction of the ball receiving portions 29). Balls 27 are housed in the recessed ribs 26. The ball receiving portions 29 and the recessed ribs 26 in the substrate 2 are formed between the first coil 22 and the second coil 23 that are adjacent in the circumferential direction when viewed in plan, with an appropriate size that corresponds to the movement distance of the wedge prism pair 3 in the rotation direction. The recessed ribs 26 and the balls 27 will be explained later. The arrow in the figure indicates the rotation direction of the wedge prism.

[0020] 1, a first Hall element 24 is disposed corresponding to the first coil 22, and a second Hall element 25 is disposed corresponding to the second coil 23. The Hall element is an element that outputs a voltage corresponding to a magnetic field formed between a magnet (described later) corresponding to the coil and a yoke. For example, in the direction along the rotation axis CA, the first Hall element and the second Hall element 25 are both disposed on the opposite side of the magnet from the coil, for example, embedded in the substrate 2. In plan view, the first Hall element 24 is disposed inside the approximately sector-shaped first coil 22, and the second Hall element 25 is disposed inside the approximately sector-shaped second coil 23. Each Hall element is connected to the CPU 21.

[0021] 2, a yoke is disposed on the main surface of substrate 2 opposite the coil. The yoke is disposed to align the direction of the magnetic field generated by the magnet with a direction along rotation axis CA and perpendicular to the direction in which the coil's conductor wire extends. That is, a first yoke 28 is disposed corresponding to first coil 22, and a second yoke is disposed corresponding to second coil 23.

[0022] As shown in Fig. 1, the wedge prism pair 3 includes a first wedge prism 31 and a second wedge prism 32. Both the first wedge prism 31 and the second wedge prism 32 have a circular planar shape, one end face perpendicular to the central axis, and the other end face inclined obliquely relative to the one end face. The inclination angle of the other end face relative to the planar direction of the one end face of the wedge prism is also called the apex angle (see Fig. 16).

[0023] A first magnet 33 is disposed corresponding to the first wedge prism 31, and a second magnet 34 is disposed corresponding to the second wedge prism 32. For example, as shown in Fig. 4, the first wedge prism 31 is fitted into a circular hole at the center of a first frame 35 in the shape of an annular plate, and the first magnet 33 is fixed to the first frame 35 on the outer periphery of the first wedge prism 31 (see Fig. 2). Similarly, the second wedge prism 32 is fitted into a circular hole at the center of a second frame in the shape of an annular plate, and the second magnet 34 is fixed to the second frame on the outer periphery of the second wedge prism 32.

[0024] As shown in FIG. 1 , the first wedge prism 31 and the second wedge prism 32 are both disposed on a circular opening in the center of the substrate 2 and are supported rotatably about a rotation axis CA. Like the substrate 2, the first frame 35 and the second frame each have the aforementioned recessed grooves, which have a planar shape along the circumferential direction, on one main surface. The aforementioned balls are accommodated in the recessed grooves. The first wedge prism 31 is placed on the substrate 2 so that the recessed grooves 26 on the first main surface of the substrate 2 face the recessed grooves 36 on the first main surface of the first frame 35. Furthermore, for example, the second wedge prism 32 is placed on the first wedge prism 31 so that the recessed grooves on the second main surface of the first frame 35 face the recessed grooves on the first main surface of the second frame.

[0025] Opposite grooves share the same balls. For example, as shown in Figure 2, ball 27 in groove 26 of substrate 2 is also accommodated in groove 36 of first frame 35. The rolling direction of ball 27 is determined by these grooves 26, 36, so that ball 27 functions as a spacer and moves while rolling when the wedge prism rotates. This allows first frame 35 and second frame 36 to rotate more smoothly.

[0026] 7 is a diagram schematically illustrating the positional relationship between magnets and coils in one embodiment of the present invention. As shown in Fig. 7, first wedge prism 31 moves as first magnet 33 held by first frame 35 passes over first coil 22 on substrate 2. Similarly, second wedge prism 32 moves as second magnet 34 held by second frame passes over second coil 23 on substrate 2.

[0027] 2, one end of the casing 4 is fixed onto one main surface of the substrate 2, and has a peripheral wall portion 41 that surrounds the first frame 35 from the outer periphery, and an annular portion 42 that extends inward from one end edge of the peripheral wall portion 41 and abuts against the second main surface of the first frame 35. The casing 4 rotatably holds the substrate 2 and the first frame 35, which overlap each other with the recessed lines 26, 36 facing each other and the balls 27 interposed therebetween, so as to maintain their positional relationship in the direction along the rotation axis CA.

[0028] In this embodiment, the above-described positional relationship in the overlapping direction between the substrate 2 and the overlapping first frame 35 can be applied to the positional relationship between the wedge prisms. That is, in this embodiment, a similar positional relationship in the overlapping direction may be established between the nth wedge prism and the (n+1)th wedge prism that are adjacent in the direction along the rotation axis CA, for example, between the first wedge prism 31 and the first frame 35 and the second wedge prism 32 and the second frame.

[0029] [Rotation of the wedge prism] The rotation of the wedge prisms in this embodiment will be described using the rotation of the first wedge prism as an example. FIG. 8 is a diagram illustrating the generation of thrust due to rotation in this embodiment of the present invention. As shown in FIG. 8, a magnetic field is formed between the first magnet 33 of the first frame 35 and the first yoke 28 in the direction indicated by the arrow M. When a current is passed through the first coil 22 in the direction shown, a thrust is generated in the direction indicated by the white arrow. The first yoke 28 and the first coil 22 are fixed to the substrate 2, and the first frame 35 is disposed rotatably relative to the substrate 2, so that the first frame 35 moves in the direction indicated by the white arrow.

[0030] FIG. 9 is a diagram illustrating the direction of thrust for rotation in an embodiment of the present invention. As described above, the first coil 22 has a generally sectorial planar shape, and its linear outer peripheral edge intersects the central axis of the planar shape at an angle of θ°. Therefore, as shown in FIG. 9 , a thrust is generated at the linear outer peripheral edge of the first coil 22 in a direction perpendicular to the outer peripheral edge in a planar view, as indicated by the hollow arrow, which rotates the first frame 35, i.e., the first wedge prism 31. The direction of this thrust is substantially along the line segment L that represents the circular locus traced by the center of the first magnet 33 when the first frame 35 rotates. In this way, the first coil 22 and the first magnet 33 constitute a voice coil motor that rotates the first wedge prism 31 when current is applied to the first coil 22.

[0031] The rotation of the wedge prism by the voice coil motor is controlled by the CPU 21. Fig. 10 is a diagram for explaining the control of the current supply to the coil in an embodiment of the present invention. As shown in Fig. 10, the Hall element outputs a voltage according to the magnetic field (magnetic flux density). The CPU 21 obtains the rotation angle (current angle) of the wedge prism according to the voltage output from the Hall element.

[0032] FIG. 11 is a diagram showing a relationship between the detection value of the Hall element and the rotation angle of the wedge prism in an embodiment of the present invention. In this embodiment of the present invention, the center position of the coil and magnet, i.e., the center of the range of rotational movement of the wedge prism, is used as the reference position of the optical axis adjustment mechanism including the wedge prism. In FIG. 11, this reference position is used as the origin (center), and changes in magnetic flux density due to rotational movement of the wedge prism are expressed as voltage values. As is clear from FIG. 11, the rotation angle of the wedge prism can be approximated by a linear equation with the voltage value (magnetic flux density) detected by the Hall element within a specific range of voltage centered on the reference position. The current angle may be calculated based on this linear equation or obtained from a map storing data on the voltage value and rotation angle within the specific range.

[0033] The specific range of magnetic flux density may be measured using an optical axis adjustment device or may be determined by calculation such as computer simulation. In this manner, CPU 21 obtains the rotation angle of first wedge prism 31 according to, for example, the magnetic flux density of the magnetic field generated by first magnet 33.

[0034] Next, the CPU 21 acquires the target rotation angle of the wedge prism (target rotation angle). FIG. 12 is a diagram schematically illustrating the relationship between the rotation angle of the wedge prism and the refraction angle of the light beam emitted from the wedge prism in an embodiment of the present invention. As shown in FIG. 12, the refraction angle of the light beam by the wedge prism can be approximated by a linear equation with respect to the rotation angle within a specific range of the wedge prism rotation angle. The target rotation angle may be acquired based on position information of another optical communication device with which optical communication should be performed relative to the position information of the optical axis adjustment device 1, or may be determined by a specific program. The specific range of the rotation angle may correspond to the range of the voltage value and rotation angle shown in FIG. 11 that can be approximated by a linear equation. In this way, the CPU 21 can calculate the position of the light beam on a plane coordinate system based on the output value from the Hall element. The CPU 21 then acquires the target rotation angle of the wedge prism based on the position information.

[0035] Next, the CPU 21 acquires information on the output value of the power that realizes the target rotation angle according to the current angle and the target rotation angle, for example, a signal according to a specific duration of on-off of the current.

[0036] Next, the CPU 21 controls the supply of power from the power supply based on the acquired information on the power output value. Thus, the power supply supplies the first coil 22 with power that realizes the target rotation angle, and the first wedge prism 31 rotates to a position that realizes the target rotation angle.

[0037] [Major effects] The optical axis adjustment device 1 includes a wedge prism that is rotatably arranged around a rotation axis CA. In this way, the optical axis adjustment device 1 uses a wedge prism as an optical element for adjusting the traveling direction of an optical beam. By controlling the traveling direction of the optical beam with the wedge prism, the optical axis adjustment device 1 absorbs misalignment of the optical components in the optical communication device that becomes apparent during transmission and reception of optical communications. In this embodiment, it is possible to control the rotation of the wedge prism with high precision, which is highly effective in improving the accuracy of optical communications.

[0038] The optical axis adjustment device 1 includes a voice coil motor for rotating the wedge prism. As mentioned above, in conventional mechanisms including a wedge prism, a hollow motor is generally used as the drive source for rotating the wedge prism. For this reason, the size and weight of the structure for rotation are larger than the wedge prism itself, and as a result, the size and weight of the optical axis adjustment device 1 are also large.

[0039] The optical axis adjustment device 1 has a voice coil motor as a rotation mechanism corresponding to each wedge prism. A typical hollow motor generates a rotational force through the attraction and repulsion of a magnetic circuit. In contrast, a voice coil motor generates a thrust force according to Fleming's left-hand rule. In this embodiment, the direction of the magnetic field and current is appropriately set based on Fleming's left-hand rule, making it possible to direct the thrust force of the voice coil motor's rotation of the wedge prism in the direction of the wedge prism's rotation. In this way, the voice coil motor generates a thrust force in the direction of the wedge prism's rotation. This suppresses the wedge prism's vibration in the thrust direction (the direction along the rotation axis CA).

[0040] Voice coil motors are advantageous for miniaturization because they require less width than other motors. Furthermore, because voice coil motors can be realized with a simple structure, the weight of the motor can be made lighter than other motors. For example, the voice coil motor may include a magnet that is integrally disposed with the wedge prism and generates a magnetic field in a direction along the rotation axis of the wedge prism. Because the voice coil motor can be configured in this way by arranging a magnet integrally with the wedge prism, this is advantageous for realizing miniaturization and weight reduction.

[0041] The voice coil motor includes a coil through which electricity flows in a direction intersecting both the rotation direction of the wedge prism and the direction of the magnetic field generated by the magnet. In this embodiment, the coil is fixed to a substrate 2, which serves as a support that rotatably supports the wedge prism. In this embodiment, the force that propels the rotation of the wedge prism generated by the voice coil motor is directed in the rotation direction of the wedge prism. This reduces loss of the propelling force from the voice coil motor. The substrate 2 is fixed to a casing 4. Therefore, the support that rotatably supports the wedge prism may be the casing 4.

[0042] In this embodiment, the planar shape of the coil is such that it generates the above-mentioned thrust in the rotation direction of the wedge prism. That is, when viewed in plan, the coil has a fan-like shape that spreads outward from the rotation axis CA of the optical axis adjustment device. Therefore, in this embodiment, the direction of current flow in the magnetic field intersects the circular rotation path of the wedge prism at an angle of 90°. Therefore, the direction of the thrust that rotates the wedge prism is substantially perpendicular to the linear outer edge of the fan-like shape, further reducing thrust loss.

[0043] The optical axis adjustment device 1 has multiple voice coil motors. Each of the multiple voice coil motors is arranged at two or more positions relative to a single wedge prism in the rotation direction of the wedge prism. While it is possible to rotate a single wedge prism using a single voice coil motor, the wedge prism may move due to attraction and repulsion in the thrust direction caused by the magnetic force of a magnet arranged on the wedge prism side. In controlling the rotation of the optical axis adjustment device 1, such movement may be determined to be a rotation.

[0044] Furthermore, when the wedge prism rotates, force tends to concentrate on one part of the wedge prism, which can easily cause vibrations as the wedge prism rotates. As a result, the rotational position of the wedge prism may be misidentified. Furthermore, the coils and magnets that make up the voice coil motor, as well as the arbitrarily placed yoke, become larger. This can lead to an imbalance in the weight of the wedge prism, which can cause the wedge prism to rotate in an elliptical pattern and not be consistent.

[0045] In this way, when one wedge prism is rotated by one voice coil motor, there is a possibility that a non-negligible error will occur in determining the rotation position of the wedge prism, and these phenomena may reduce the communication accuracy of the light beam.

[0046] In a configuration in which the optical axis adjustment device 1 has multiple voice coil motors, the multiple coils can be arranged in a balanced manner in the rotation direction of the wedge prism. For example, when the wedge prism is viewed in a plan view, each of the multiple voice coil motors is arranged in a rotationally symmetrical position around the rotation axis CA. In this way, a so-called equal pitch is adopted, and magnetic circuits are formed at equally spaced positions on a specific circumference. This prevents the magnetic circuits from concentrating in one area, and further suppresses displacement of the wedge prism in the thrust direction. This makes it easier to stabilize the performance of the optical axis adjustment device.

[0047] The optical axis adjustment device 1 includes a CPU 21, which is a control device for controlling the power supply to the voice coil motor in accordance with the rotation angle of the wedge prism, which corresponds to a specific orientation of the optical axis of light emitted from the wedge prism. To detect this rotation angle, Hall elements are used to detect the magnetic flux density of the magnetic fields formed by the first magnet 33 and the second magnet 34. Specifically, the CPU 21 obtains the rotation angle of the wedge prism that achieves a specific orientation of the optical axis of light emitted from the wedge prism in accordance with the magnetic flux density detected by the Hall elements. In this manner, in this embodiment, the rotation angle of the wedge prism is electronically controlled. Therefore, the rotation angle of the wedge prism can be controlled with greater precision than by using a gear mechanism.

[0048] Generally, the direction of the optical axis of a light beam using a wedge prism is controlled by rotating the wedge prism. The movement of the light beam due to this rotation is simply caused by refraction due to the apex angle of the wedge prism. In this embodiment, the optical axis adjusting device 1 has a pair of wedge prisms. By combining the two wedge prisms, the direction of the optical axis of the light beam emitted from the optical axis adjusting device 1 is controlled by its position in a plane coordinate system perpendicular to the rotation axis.

[0049] FIG. 13 is a diagram illustrating adjustment of the direction of the optical axis of a light beam using a pair of wedge prisms in an embodiment of the present invention. As shown in FIG. 13, in the wedge prism pair 3, the first wedge prism 31 and the second wedge prism 32 are each rotated. The arrows in the figure indicate the rotation directions of the wedge prisms in the wedge prism pair 3. This makes it possible to adjust the direction of the optical axis of light passing through the wedge prisms in any direction perpendicular to the rotation axis CA. Note that in FIGS. 13 and 14, the arrows in the figures indicate the rotation directions of the wedge prisms in the wedge prism pair 3.

[0050] FIG. 14 is a diagram illustrating the adjustment of the direction of the optical axis of a light beam by two pairs of wedge prisms in an embodiment of the present invention. If it is desired to reduce the rotation angle of each wedge prism or to increase the refraction angle of the light beam, this can be achieved by increasing the number of wedge prisms. In other words, in this case, it is sufficient to provide additional wedge prisms and magnets and appropriately position coils corresponding to the magnets. Thus, there may be multiple wedge prism pairs 3, and as shown in FIG. 14, there may be two wedge prism pairs 3 (four wedge prisms).

[0051] In this embodiment, the optical axis adjustment device 1 may have two pairs of wedge prisms, or may have more than two pairs of wedge prisms. Increasing the number of wedge prisms arranged along the rotation axis CA allows the desired refraction angle of the light beam to be achieved with a smaller rotation angle of the wedge prisms. Increasing the number of wedge prisms and reducing the rotation angle of the wedge prisms reduces the rotational movement distance of each wedge prism, which is advantageous for speeding up the adjustment of the direction of the optical axis of the light beam.

[0052] Optical beam communications have a function for locating communication partners (beacons, described below). Such a search for a communication partner involves randomly irradiating a light beam to locate the partner's location. One example of a search using optical beam irradiation involves designating a specific rectangular planar area and scanning the planar area with the light beam. A more specific example involves repeatedly scanning the planar area horizontally (from left to right, from right to left) with the light beam while sequentially changing its vertical position until the communication partner is detected. In such optical beam scanning, the smaller the rotation angle of the wedge prism, the smaller the rotational movement distance of the wedge prism, and the more rapidly the direction of the optical axis of the light beam changes. This allows for faster scanning of the optical beam, resulting in more rapid detection of the communication partner. Thus, having two or more pairs of wedge prisms is even more effective in scanning a high-frequency optical beam that moves rapidly and periodically within a certain range.

[0053] Furthermore, the casing 4 is usually susceptible to vibration due to high-frequency electrode supply. Increasing the number of wedge prisms and reducing the rotation angle of the wedge prisms is also advantageous from the perspective of suppressing vibration of the casing 4 due to electrode supply.

[0054] In this embodiment, adjacent components that can rotate relative to each other in the direction along the rotation axis CA, such as the substrate 2, the first frame 35, and the second frame, have grooves 26, 36 on their opposing main surfaces and are adjacent to each other in the direction along the rotation axis CA via balls 27 housed in the grooves. This allows the wedge prism to rotate smoothly in its rotation direction. Furthermore, adjusting the size of the balls ensures a constant clearance between the coil and the magnet. As a result, the magnetic field generated by the magnet is stable regardless of whether the wedge prism rotates.

[0055] In this embodiment, the thrust force in the rotation direction when the wedge prism is energized is essentially used only to rotate the wedge prism. In this embodiment, the casing 4 restrains the wedge prism in the direction along the rotation axis CA (thrust direction). Therefore, regardless of whether the wedge prism rotates, the position of the wedge prisms in the thrust direction is fixed. As a result, a stable magnetic field is formed and stable rotation of the wedge prism is achieved.

[0056] In this embodiment, three first coils 22 are arranged at positions with three-fold rotational symmetry, and an electrical circuit is formed in which each first coil 22 is connected in series to a power source. Because multiple coils are energized by a common power source in this manner, in this embodiment, the timing of energizing the three voice coil motors that rotate the first wedge prism 31 is substantially simultaneous. Therefore, sliding of the wedge prism, which occurs at the beginning of the rotation, is unlikely to occur. Furthermore, because the electrical circuit for the coils is simply configured, this is particularly effective when the optical axis adjustment device 1 has a large number of wedge prisms (for example, two or more pairs).

[0057] Furthermore, power can be supplied to the coil by switching drive using pulse width modulation (PWM) as described above. In this case, it is preferable to further reduce power loss caused by turning the power supply on and off. From the viewpoint of reducing such power loss, an electric circuit configuration with fewer switching parts, such as the above-mentioned series circuit, is preferable.

[0058] [Optical communication device] An optical communication device according to an embodiment of the present invention includes the optical axis adjustment device according to the embodiment of the present invention. The optical communication device further includes a light-emitting element if it is a transmitting device, or a light-receiving element if it is a receiving device.

[0059] Optical semiconductors can be used for the light-emitting element and the light-receiving element. The light-emitting element may be, for example, an element that converts electricity into light. Examples of the light-emitting element include a light-emitting diode and a semiconductor laser. The light-receiving element may be, for example, an element that converts light into electricity. Examples of the light-receiving element include a photodiode and a CMOS image sensor.

[0060] The optical communication device of this embodiment may further include other components in addition to the optical axis adjustment device or the light emitting element and the light receiving element, as long as the effects of this embodiment can be obtained. Examples of such other components include optical elements such as a condensing lens and a diffusing lens, a mount for rotatably supporting the light emitting element or the light receiving element and the optical axis adjustment device, a wireless communication device for transmitting and receiving signals from the optical communication device to a user, or from the user to the optical communication device, etc.

[0061] FIG. 15 is a diagram schematically illustrating the configuration of an optical communication device according to one embodiment of the present invention. As shown in FIG. 15, the optical communication device 100 includes a light-emitting element 110 and an optical axis adjustment device 120. The optical axis adjustment device 120 has the same configuration as the optical axis adjustment device 1 described above, except that it includes two wedge prism pairs 3A and 3B. A plane perpendicular to the rotation axis CA of the wedge prism is defined as the yaw direction, and a vertical direction on the plane is defined as the pitch direction. One wedge prism pair 3A of the optical axis adjustment device controls refraction in the pitch direction, for example. The other wedge prism pair 3B of the optical axis adjustment device controls refraction in the pitch direction, for example.

[0062] The optical communication device 100 is suitable for use in a beacon. A beacon emits a light beam over a wide area to notify the other party of its location. It is difficult to accurately capture the location of a communication partner in a large space. In a beacon, the light beam is directed in an approximate direction and emitted within the search area. This search can be performed by scanning the light beam, as described above. The light emission direction is determined by combining the pitch angle and yaw angle.

[0063] The optical communication device 100 may have a mechanism for further turning the optical axis adjustment device to a specific direction. This mechanism may be configured using, for example, a motor, and may be appropriately selected from mechanisms that do not substantially generate vibrations while the optical axis adjustment device is turned to a specific direction.

[0064] Like the optical axis adjustment device 1, the optical axis adjustment device 120 employs a wedge prism rotation system that employs a voice coil motor. This makes it suitable for achieving compactness and lightness. Furthermore, the realization of compactness and lightness enables even higher speed driving. As a result, it is possible to irradiate the irradiation range for searching for a communication partner with an optical beam in a shorter time than with conventional optical communication devices, and it is also possible to find the communication partner more quickly.

[0065] FIG. 16 is a diagram schematically illustrating the configuration of a conventional optical communication device. As shown in FIG. 16, a conventional optical communication device 200, such as an optical communication device with a gimbal mechanism, includes a main body 210 having an irradiation optical system including a light-emitting element, and a mount 220 supporting the main body 210. The main body 210 further includes a first hollow motor that rotates the irradiation optical system in the pitch direction. The mount 220 further includes a second hollow motor that rotates the main body 210 in the yaw direction. The optical communication device 200 with a gimbal mechanism requires two hollow motors for rotating the irradiation optical system in two directions, in addition to the irradiation optical system. This increases the size of the optical communication device 200. Furthermore, the hollow motors are likely to generate micro-vibrations when the main body 210 and the mount 220 rotate, causing the light beam from the irradiation optical system to vibrate and reducing the accuracy of optical communication.

[0066] Other Embodiments An embodiment of the present invention relates to a technology for improving the accuracy of optical axis adjustment in an optical axis adjustment device, which is a technology for refracting a transmission path of an optical beam using a wedge prism in optical communications and converging the optical beam within a specified range. The embodiment of the present invention may include configurations other than those described above, as long as the effects of the embodiment of the present invention can be obtained.

[0067] For example, in an embodiment of the present invention, the arrangement and size of the coils corresponding to the wedge prisms do not have to be uniform. When performing optical beam communication, it is preferable that the mounting state of the optical communication device is not always the same, but that various mounting positions can be accommodated. Figure 17 is a diagram schematically illustrating a first example of coil arrangement when the center of gravity of the rotating body in an embodiment of the present invention is deviated from the rotation axis. Figure 18 is a diagram schematically illustrating a second example of coil arrangement when the center of gravity of the rotating body in an embodiment of the present invention is deviated from the rotation axis.

[0068] For example, as shown in Fig. 17, the position of the center of gravity G1 of the rotating body (e.g., first frame, magnet) in a particular posture of the optical communication device may be shifted from the center (rotation axis CA) of the planar shape of the rotating body. In this case, one of the three evenly spaced first coils 22 may be replaced with a first coil 22A having a larger number of turns. In this case, when the center of the rotating body is shifted as shown in Fig. 17, the output of the voice coil motor with the larger coil will be greater than the other voice coil motors, which is preferable from the perspective of achieving smooth rotation.

[0069] 18, when the position of the center of gravity G2 of the rotor in a specific orientation of the optical communication device is shifted from the center (rotation axis CA) of the planar shape of the rotor, more coils may be arranged at positions closer to the center of gravity G2. For example, in a specification in which three first coils 22 are arranged at equal intervals, one first coil 22 may be replaced with two first coils 22B, 22B arranged at positions on either side of the center of gravity. In such a case, since the number of first coils 22 increases from three to four, it is preferable to arrange the first coils at positions with four-fold rotational symmetry so that the four first coils are equally spaced.

[0070] The coil arrangements shown in FIGS. 17 and 18 are advantageous in terms of stabilizing the performance of optical communications, regardless of the mounting orientation of the optical communications device.

[0071] In an embodiment of the present invention, as shown in FIG. 19, a power supply may be connected to each coil to supply power to the coil. FIG. 19 is a diagram schematically illustrating another example of an electrical circuit between the coil and the power supply in an embodiment of the present invention. In a configuration in which a power supply is connected to each coil individually, if the position of the center of gravity G of the rotating body described above is offset from the center of rotation of the rotating body, it is possible to further stabilize the rotation of the rotating body by individually and appropriately setting the amount of current supplied to each coil. Therefore, such a configuration is also advantageous from the viewpoint of stabilizing the performance of optical communication regardless of the mounting orientation of the optical communication device.

[0072] In an embodiment of the present invention, the range in which the rotation angle of the wedge prism according to the magnetic flux density of the magnetic field generated by the magnet can be approximated by a linear equation can be adjusted appropriately according to the magnetic field generated, the power supplied, etc.

[0073] Embodiments of the present invention are effective in enabling faster adjustment of the optical axis of an optical beam. In optical beam communications, the communication partner is not always fixed; rather, the positional relationship with the communication partner may change relative to the communication partner, such as by moving slowly. Even in such cases, if the communication partner's range of movement is predictable and the optical axis direction of the optical beam can be adjusted to match the communication partner, the communication state can be maintained by tracking the optical beam. In other words, if the communication partner's position is known to change in advance, or if there is a possibility that communication with the communication partner will be interrupted, periodic status checks can be performed using the beacon described above to ensure stable communication. Compared to radio wave communications, more directional communication methods such as optical communications require the position of the communication partner to be constantly determined with high accuracy. In embodiments of the present invention, the position of the communication partner in optical communications can be determined with high accuracy by controlling the rotation of the wedge prism using the electronic technology described above and employing a high-precision actuator including the specific voice coil motor described above.

[0074] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0075] 〔summary〕 As is clear from the above description, the optical axis adjustment device (1) according to an embodiment of the present invention includes a wedge prism (such as the first wedge prism 31) rotatably arranged about a rotation axis (CA), a voice coil motor for rotating the wedge prism, and a control device (CPU 21) for controlling the power supply to the voice coil motor in accordance with the rotation angle of the wedge prism corresponding to a specific direction of the optical axis of light emitted from the wedge prism. Furthermore, the optical axis adjustment device (100) according to an embodiment of the present invention includes the optical axis adjustment device according to the embodiment of the present invention described above. Therefore, the embodiment of the present invention can achieve more accurate control of the traveling direction of the light beam using the wedge prism than conventional optical axis adjustment devices that use, for example, the aforementioned hollow motor as a rotation drive source.

[0076] The voice coil motor may have a magnet (such as first magnet 33) fixed to the wedge prism for generating a magnetic field in a direction along the rotation axis of the wedge prism, and a coil (such as first coil 22) fixed to a support (such as substrate 2) that rotatably supports the wedge prism and has a portion extending in a direction intersecting both the rotation direction of the wedge prism and the direction of the magnetic field. This configuration is even more effective from the perspective of realizing a smaller and lighter optical axis adjustment device.

[0077] The coil may have a fan-like shape that spreads outward from the rotation axis in a plan view, which is even more effective in reducing loss of thrust force during rotation of the wedge prism.

[0078] The optical axis adjustment device may further include a Hall element for detecting the magnetic flux density of the magnetic field generated by the magnet, and the control device may obtain the rotation angle of the wedge prism that realizes a specific orientation of the optical axis of the light emitted from the wedge prism in accordance with the magnetic flux density detected by the Hall element. This configuration is even more effective from the viewpoint of quickly and easily determining the rotation angle of the wedge prism.

[0079] The optical axis adjustment device may have multiple voice coil motors, and the voice coil motors may be arranged at two or more locations in the rotation direction of one wedge prism, which is even more effective in terms of improving the stability of the performance of the optical axis adjustment device.

[0080] The voice coil motors may be arranged at positions rotationally symmetrical about the rotation axis when the wedge prism is viewed from above, which is even more effective in suppressing thrust direction displacement of the wedge prism due to concentration of magnetic circuitry.

[0081] The optical axis adjustment device may have a pair of wedge prisms. This configuration is more effective from the viewpoint of reducing the rotation angle of the wedge prisms and suppressing the generation of vibrations due to power supply. The optical axis adjustment device may have two or more pairs of wedge prisms. This configuration is even more effective from the viewpoint mentioned above.

[0082] The optical axis adjustment device and optical communication device according to the embodiments of the present invention are expected to realize more power-saving and more accurate optical communication. This is expected to lead to further improvements in industrial productivity and further economic growth. In this way, the embodiments of the present invention are expected to contribute to the achievement of the Sustainable Development Goals (SDGs). [Explanation of symbols]

[0083] 1, 120 Optical axis adjustment device 2 boards 3, 3A, 3B, 140 Wedge Prism Pair 4 Casing 21 CPU (controller) 22, 22A, 22B First coil 23 Second coil 24 First Hall element 25 Second Hall element 26, 36 grooves 27 balls 28 First York 29 Ball receiving part 31 First wedge prism 32 Second wedge prism 33 First magnet 34 Second magnet 35 First slot 41 Peripheral wall section 42 Annular part 100, 200 Optical communication device 110 Light-emitting element 130 Lens 210 Main Unit 220 Mounting stand CA Rotation Axis G1, G2 center of gravity LB Light Beam

Claims

1. a wedge prism that is rotatably disposed around a specific axis; a plurality of voice coil motors for rotating the wedge prism; a control device for controlling energization of the voice coil motor in accordance with a rotation angle of the wedge prism corresponding to a specific direction of the optical axis of the light emitted from the wedge prism; and the voice coil motors are arranged at two or more positions for one of the wedge prisms in the rotation direction of the wedge prism, the plurality of voice coil motors are arranged at positions rotationally symmetrical about the rotation axis when the wedge prism is viewed in a plane; Optical axis adjustment device.

2. The voice coil motor is a magnet fixed to the wedge prism for generating a magnetic field in a direction along the rotation axis of the wedge prism; a coil fixed to a support that rotatably supports the wedge prism and including a portion extending in a direction intersecting both the rotation direction of the wedge prism and the direction of the magnetic field; The optical axis adjusting device according to claim 1 , further comprising:

3. The optical axis adjusting device according to claim 2 , wherein the coil has a fan-like shape that spreads outward from the rotation axis when viewed in a plan view.

4. further comprising a Hall element for detecting the magnetic flux density of the magnetic field; the control device acquires a rotation angle of the wedge prism that realizes a specific orientation of the optical axis of the light emitted from the wedge prism, in accordance with a value of the magnetic flux density detected by the Hall element.

4. The optical axis adjusting device according to claim 2 or 3.

5. 5. The optical axis adjusting device according to claim 1, further comprising a pair of the wedge prisms.

6. 5. The optical axis adjusting device according to claim 1, wherein the optical axis adjusting device comprises two or more pairs of the wedge prisms.

7. An optical communication device comprising the optical axis adjusting device according to any one of claims 1 to 6.

Images