JP7748841B2 - Optical axis adjustment device and optical communication device - Google Patents

Description

The present invention relates to an optical axis adjustment device and an optical communication device.

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

International Publication No. 2016/024340

Hollow motors are structurally prone to generating micro-vibrations. Therefore, when using a hollow motor 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. As such, there is still room for improvement in the control of the direction of travel of light beams using wedge prisms in optical communications, with the aim of achieving even more precise control.

One aspect of the present invention aims to achieve highly accurate control of the direction of travel of a light beam using a wedge prism.

In order to solve the above problem, an optical axis adjustment device according to one aspect of the present invention comprises a wedge prism that is rotatably arranged 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.

Furthermore, in order to solve the above-mentioned problems, an optical communication device according to one aspect of the present invention is equipped with the optical axis adjustment device of the present invention.

According to one aspect of the present invention, it is possible to control the direction of a light beam using a wedge prism with high precision.

1 is a diagram schematically illustrating a configuration of an optical axis adjusting device according to an embodiment of the present invention. 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; FIG. 2 is a plan view schematically showing a coil according to an embodiment of the present invention. FIG. 10 is a diagram schematically illustrating the arrangement of coils arranged corresponding to a wedge prism in one embodiment of the present invention. FIG. 2 is a diagram illustrating an example of an electric circuit including a coil according to an embodiment of the present invention. 3A and 3B are diagrams schematically showing grooves formed on a substrate in an embodiment of the present invention. 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. 10A and 10B are diagrams for explaining the generation of thrust force during rotation in an embodiment of the present invention. 10A and 10B are diagrams for explaining the direction of thrust force of rotation in the embodiment of the present invention. 5A and 5B are diagrams for explaining control of current supply to a coil in the embodiment of the present invention. 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. 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. 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. 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. 1 is a diagram schematically illustrating a configuration of an optical communication device according to an embodiment of the present invention. FIG. 1 is a diagram schematically illustrating an example of the configuration of a conventional optical communication device. 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. 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. 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. FIG. 10 is a diagram schematically illustrating another example of the configuration of a conventional optical communication device.

[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 the 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.

The substrate 2 is a plate material that has a circular ring shape when viewed 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 the rotation axis CA.

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 to the first coil 22 and the second coil 23 from a power supply (not shown). The first coil 22 and the second coil 23 are arranged on one main surface of the substrate 2.

Figure 3 is a plan view schematically illustrating a coil according to one embodiment of the present invention. As shown in Figure 3, both the first coil 22 and the second coil 23 are constructed of conductive wire wound in a generally fan-shaped configuration when viewed in plan. Note that the angle θ represents the angle between the direction along the central axis of the generally fan-shaped first coil 22 and the second coil 23 and the linear outer edge of the generally fan-shaped configuration. In this way, both the first coil 22 and the second coil 23 have a fan-shaped configuration that spreads outward from the rotation axis when viewed in plan.

Multiple first coils 22 and multiple second coils 23 are arranged, and each first coil 22 or second coil 23 is arranged in a rotationally symmetrical position when viewed in a plane. The first coils 22 and second coils 23 are arranged in the same manner.

Figure 4 is a diagram showing the arrangement of coils corresponding to the wedge prism in one embodiment of the present invention. For example, as shown in Figure 4, the first coil 22 is arranged in a position of three-fold rotational symmetry with the rotation axis CA as the center of rotation when viewed from above. The second coil 23 is also arranged in a position of three-fold rotational symmetry similar to the first coil 22. In Figure 4, reference numeral 31 denotes the first wedge prism, which will be described later, and reference numeral 35 denotes the first frame, which will be described later.

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 offset from each other when viewed in a plan view. 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 degrees from each other.

The first coil 22 and the second coil 23 are each connected to a power source. Figure 5 is a schematic diagram showing an example of an electrical circuit including coils in one embodiment of the present invention. As shown in Figure 5, three first coils 22 are connected in series to a power source, and three second coils 23 are connected in series to a power source.

Figure 6 is a schematic diagram showing the grooves formed on a substrate in an embodiment of the present invention. As shown in Figure 2, substrate 2 has a ball receiving portion 29 on one main surface. Ball receiving portion 29 is a protrusion portion whose planar shape is an arc. A groove 26 is formed at the top of ball receiving portion 29 along the longitudinal direction of ball receiving portion 29.

As shown in Figure 6, the recessed rib 26 has a planar shape that runs along the circumferential direction of the substrate 2 (the long axis direction of the ball receiving portion 29). A ball 27 is accommodated in the recessed rib 26. The ball receiving portion 29 and recessed rib 26 on 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 in the rotation direction of the wedge prism pair 3. The recessed rib 26 and ball 27 will be explained later. Note that the arrow in the figure indicates the rotation direction of the wedge prism.

As shown in FIG. 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 force corresponding to the magnetic field formed between the yoke and a magnet (described later) corresponding to the coil. 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 approximate sector of the first coil 22, and the second Hall element 25 is disposed inside the approximate sector of the second coil 23. Each Hall element is connected to the CPU 21.

Furthermore, as shown in FIG. 2, a yoke is disposed on the main surface of the substrate 2 opposite the coil. The yoke is disposed to align the direction of the magnetic field generated by the magnet in a direction along the 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 the first coil 22, and a second yoke is disposed corresponding to the second coil 23.

As shown in Figure 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 their central axes, and the other end face inclined obliquely relative to the one end face. The angle of inclination 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 Figure 16).

A first magnet 33 is arranged corresponding to the first wedge prism 31, and a second magnet 34 is arranged corresponding to the second wedge prism 32. For example, as shown in FIG. 4, the first wedge prism 31 is fitted into a central circular hole in a first annular plate-shaped frame 35, 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 central circular hole in a second annular plate-shaped frame, and the second magnet 34 is fixed to the second frame on the outer periphery of the second wedge prism 32.

As shown in FIG. 1, the first wedge prism 31 and the second wedge prism 32 are both positioned on a circular opening in the center of the substrate 2 and are supported rotatably around a rotation axis CA. Like the substrate 2, the first frame 35 and the second frame both have the aforementioned recessed grooves on one main surface, which have a planar shape along the circumferential direction. The aforementioned balls are accommodated in these recessed grooves. The first wedge prism 31 is then 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.

Opposing grooves share the balls housed in the grooves. For example, as shown in Figure 2, ball 27 in groove 26 of substrate 2 is also housed in groove 36 of first frame 35. These grooves 26, 36 determine the rolling direction of ball 27, allowing ball 27 to function as a spacer and to move while rolling when the wedge prism rotates. This allows first frame 35 and second frame 36 to rotate more smoothly.

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

As shown in Figure 2, the casing 4 has one end fixed to 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 edge of the peripheral wall portion 41 and abuts 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 via the balls 27 with the recesses 26, 36 facing each other, so as to maintain their positional relationship in the direction along the rotation axis CA.

In this embodiment, the above-described positional relationship in the overlapping direction between the substrate 2 and the overlapping first frame 35 can also be applied to the positional relationship between the wedge prisms. That is, in this embodiment, a similar positional relationship in the overlapping direction may exist 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 first frame 35 and the second wedge prism 32 and second frame.

[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. Figure 8 is a diagram for explaining the generation of thrust due to rotation in this embodiment of the present invention. As shown in Figure 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 arrow M. When a current is passed through the first coil 22 in the illustrated direction, a thrust is generated in the direction indicated by the open 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 open arrow.

Figure 9 is a diagram illustrating the direction of rotational thrust 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 Figure 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 indicates the circular trajectory 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.

The rotation of the wedge prism by the voice coil motor is controlled by the CPU 21. Figure 10 is a diagram for explaining the control of coil current flow in an embodiment of the present invention. As shown in Figure 10, the Hall element outputs a voltage corresponding 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.

Figure 11 is a diagram schematically illustrating the 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 for the optical axis adjustment mechanism including the wedge prism. In Figure 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 Figure 11, the rotation angle of the wedge prism can be approximated by a linear equation using 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 may be obtained from a map storing data on the voltage value and rotation angle within that specific range.

The above-mentioned 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 way, the CPU 21 obtains the rotation angle of the first wedge prism 31 according to, for example, the magnetic flux density of the magnetic field generated by the first magnet 33.

Next, the CPU 21 obtains the target rotation angle of the wedge prism (target rotation angle). Figure 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 Figure 12, the refraction angle of the light beam by the wedge prism can be approximated by a linear equation with the rotation angle within a specific range of the wedge prism rotation angle. The target rotation angle may be obtained based on position information of other optical communication devices 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 rotation angles may correspond to the range of voltage values and rotation angles shown in Figure 11 that can be approximated by a linear equation. In this way, the CPU 21 can calculate the position of the light beam on planar coordinates based on the output value from the Hall element. The CPU 21 then obtains the target rotation angle of the wedge prism based on the position information.

Next, the CPU 21 obtains information on the power output value that achieves the target rotation angle based on the current angle and the target rotation angle, for example, a signal corresponding to a specific on-time width when the current is turned on and off.

The CPU 21 then controls the supply of power from the power supply based on the acquired power output value information. Thus, the first coil 22 is supplied with power from the power supply to achieve the target rotation angle, and the first wedge prism 31 rotates to a position that achieves the target rotation angle.

[Major effects]
The optical axis adjustment device 1 includes a wedge prism that is rotatably disposed about a rotation axis CA. In this manner, 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 using 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.

The optical axis adjustment device 1 includes a voice coil motor for rotating the wedge prism. As mentioned above, in conventional mechanisms including wedge prisms, a hollow motor is generally used as the drive source for rotating the wedge prism. As a result, 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 large.

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 rotational force through the attraction and repulsion of a magnetic circuit. In contrast, a voice coil motor generates thrust in accordance with 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 of the voice coil motor's rotation of the wedge prism in the direction of rotation of the wedge prism. In this way, the voice coil motor generates thrust in the direction of rotation of the wedge prism. This suppresses shaking of the wedge prism in the thrust direction (along the rotation axis CA).

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

The voice coil motor includes a coil through which electricity flows in a direction that intersects 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 the 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 direction of rotation of the wedge prism. This reduces loss of the propelling force from the voice coil motor. The substrate 2 is fixed to the casing 4. Therefore, the support that rotatably supports the wedge prism may be the casing 4.

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 is a direction that intersects the circular rotation orbit 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.

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 rotational direction of the wedge prism. While it is possible to rotate a single wedge prism using a single voice coil motor, the magnetic force of a magnet arranged on the wedge prism side may cause the wedge prism to move due to attraction and repulsion in the thrust direction. When controlling the rotation of the optical axis adjustment device 1, such movement may be judged as rotation.

In addition, when the wedge prism rotates, force tends to concentrate on one part of the wedge prism, which makes it more likely to vibrate as it 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 may cause the wedge prism to rotate in an elliptical pattern and not be constant.

As such, when one wedge prism is rotated by one voice coil motor, there is a possibility that non-negligible errors may occur in determining the rotational position of the wedge prism, and these events may result in a decrease in the accuracy of light beam communication.

When the optical axis adjustment device 1 is configured with multiple voice coil motors, the multiple coils can be arranged in a balanced manner in the rotational direction of the wedge prism. For example, each of the multiple voice coil motors is arranged in a rotationally symmetrical position around the rotation axis CA when the wedge prism is viewed in a plan view. 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.

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 the light emitted from the wedge prism. To detect this rotation angle, a Hall element is used to detect the magnetic flux density of the magnetic fields formed by the first magnet 33 and the second magnet 34. In other words, the CPU 21 obtains the rotation angle of the wedge prism that achieves 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. In this manner, in this embodiment, the rotation angle of the wedge prism is electronically controlled. Therefore, the rotation angle of the wedge prism is controlled with greater precision than when the rotation angle is controlled by a gear mechanism.

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 adjustment 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 adjustment device 1 is controlled by its position in a plane coordinate system perpendicular to the rotation axis.

Figure 13 is a diagram illustrating the adjustment of the optical axis direction of a light beam using a pair of wedge prisms in an embodiment of the present invention. As shown in Figure 13, the first wedge prism 31 and the second wedge prism 32 in the wedge prism pair 3 are each rotated. The arrows in the figure indicate the rotation direction 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 Figures 13 and 14, the arrows in the figures indicate the rotation direction of the wedge prisms in the wedge prism pair 3.

Figure 14 is a diagram illustrating the adjustment of the direction of the optical axis of a light beam using 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 place more wedge prisms and magnets and appropriately position coils corresponding to the magnets. In this way, there may be multiple wedge prism pairs 3, and as shown in Figure 14, there may be two wedge prism pairs 3 (four wedge prisms).

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 side by side along the rotation axis CA makes it possible to achieve the desired refraction angle of the light beam through the wedge prisms 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.

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

In addition, the casing 4 is typically 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.

In this embodiment, adjacent components that can rotate relatively in the direction along the rotation axis CA, such as the substrate 2, first frame 35, and second frame, have grooves 26, 36 on their opposing main surfaces and are adjacent 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, by adjusting the size of the balls, the clearance between the coil and the magnet is kept constant. As a result, the magnetic field generated by the magnet is stable regardless of whether the wedge prism rotates or not.

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 between 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.

In this embodiment, three first coils 22 are arranged in positions with three-fold rotational symmetry, and an electrical circuit is formed that connects each first coil 22 in series to a power source. Because multiple coils are energized by a common power source in this way, in this embodiment, the timing of energization to the three voice coil motors that rotate the first wedge prism 31 is substantially simultaneous. Therefore, the sliding movement of the wedge prism that occurs at the beginning of the rotation is less likely to occur. Furthermore, because the coil electrical circuit 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).

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 perspective of reducing such power loss, an electrical circuit configuration with fewer switching parts, such as the above-mentioned series circuit, is preferable.

[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.

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 light-emitting elements include light-emitting diodes and semiconductor lasers. The light-receiving element may be, for example, an element that converts light into electricity. Examples of light-receiving elements include photodiodes and CMOS image sensors.

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 achieved. Examples of such other components include optical elements such as a focusing lens and a diffusing lens, a mount for rotatably supporting the light-emitting element or light-receiving element and the optical axis adjustment device, and a wireless communication device for transmitting and receiving signals from the optical communication device to a user or from a user to the optical communication device.

Figure 15 is a diagram schematically illustrating the configuration of an optical communication device according to one embodiment of the present invention. As shown in Figure 15, the optical communication device 100 has 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 has two wedge prism pairs 3A and 3B. The plane is perpendicular to the rotation axis CA of the wedge prism, and the horizontal direction in this plane is the yaw direction, and the vertical direction in this plane is 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.

The optical communication device 100 is suitable for use in beacons. 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.

The optical communication device 100 may have an additional rotation mechanism for pointing the optical axis adjustment device in a specific direction. This additional mechanism may be constructed using, for example, a motor, and may be appropriately selected from mechanisms that generate substantially no vibration while the optical axis adjustment device is pointed in a specific direction.

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 ideal for achieving compactness and light weight. Furthermore, the ability to achieve compactness and light weight allows for even faster driving. As a result, the irradiation range for searching for a communication partner using an optical beam can be expanded in a shorter time than with conventional optical communication devices, making it possible to find the communication partner more quickly.

Figure 16 is a diagram schematically illustrating the configuration of a conventional optical communication device. As shown in Figure 16, a conventional optical communication device 200, for example, 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 that supports 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 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 mount 220 rotate, causing the light beam from the irradiation optical system to vibrate and reducing the accuracy of optical communication.

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.

For example, in an embodiment of the present invention, the placement 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, and that various mounting positions can be tolerated. Figure 17 is a diagram schematically showing a first example of coil placement 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 showing a second example of coil placement when the center of gravity of the rotating body in an embodiment of the present invention is deviated from the rotation axis.

For example, as shown in Figure 17, the position of the center of gravity G1 of the rotating body (e.g., first frame, magnet) in a particular orientation 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 with a larger number of turns. In this case, when the center of the rotating body is shifted as shown in Figure 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.

Furthermore, as shown in FIG. 18, if the position of the center of gravity G2 of the rotor in a particular 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 placed closer to the center of gravity G2. For example, in a specification in which three first coils 22 are placed at equal intervals, one first coil 22 may be replaced with two first coils 22B, 22B placed 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 place the first coils at positions with four-fold rotational symmetry so that the four first coils are equally spaced.

The coil arrangement shown in Figures 17 and 18 is advantageous in terms of stabilizing optical communication performance regardless of the mounting position of the optical communication device.

In an embodiment of the present invention, as shown in Figure 19, a power supply may be connected to each coil to supply power to the coil. Figure 19 is a diagram schematically illustrating another example of an electrical circuit between a coil and a 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 aforementioned rotating body is offset from the center of rotation of the rotating body, it is possible to make the rotation of the rotating body more stable by individually and appropriately setting the amount of current flowing to each coil. Therefore, this configuration is also advantageous from the perspective of stabilizing the performance of optical communications regardless of the mounting orientation of the optical communications device.

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

Embodiments of the present invention are effective in enabling faster adjustment of the optical axis of a light beam. In optical beam communications, the communication partner is not necessarily fixed at all times; rather, the positional relationship with the communication partner may change relatively, such as by moving slowly. Even in such cases, if the communication partner's range of movement is predictable and the optical axis of the light beam can be adjusted to match the communication partner, the communication state can be maintained by tracking the light beam. In other words, if there is a possibility that communication with the communication partner will be interrupted, such as when it is known in advance that the communication partner's position will change, 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.

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.

〔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 energization of the voice coil motor in accordance with the rotation angle of the wedge prism corresponding to a specific orientation 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 highly accurate control of the traveling direction of the light beam using the wedge prism, compared to, for example, a conventional optical axis adjustment device that uses the aforementioned hollow motor as a rotation drive source.

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 in terms of achieving a smaller and lighter optical axis adjustment device.

The coil may have a fan-like shape that spreads outward from the axis of rotation when viewed in a plane. This configuration is even more effective in reducing loss of thrust force during rotation of the wedge prism.

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 achieves a specific orientation of the optical axis of the light emitted from the wedge prism based on the magnetic flux density detected by the Hall element. This configuration is even more effective in terms of quickly and easily determining the rotation angle of the wedge prism.

The optical axis adjustment device may have multiple voice coil motors, with the voice coil motors being arranged at two or more locations in the rotation direction of a single wedge prism. This configuration is even more effective in terms of improving the stability of the performance of the optical axis adjustment device.

Each of the multiple voice coil motors may be arranged at positions rotationally symmetrical about the rotation axis when the wedge prism is viewed in a plan view. This configuration is even more effective in preventing the wedge prism from displacing in the thrust direction due to concentration of magnetic circuitry.

The optical axis adjustment device may have a pair of wedge prisms. This configuration is more effective from the perspective of reducing the rotation angle of the wedge prisms and suppressing the generation of vibrations associated with power supply. The optical axis adjustment device may have two or more pairs of wedge prisms. This configuration is even more effective from the above perspective.

The optical axis adjustment device and optical communication device according to the embodiments of the present invention are expected to realize more energy-efficient and more accurate optical communications. 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).

1, 120 Optical axis adjustment device 2 Substrate 3, 3A, 3B, 140 Wedge prism pair 4 Casing 21 CPU (control device)
22, 22A, 22B First coil 23 Second coil 24 First hall element 25 Second hall element 26, 36 Concave rib 27 Ball 28 First yoke 29 Ball receiving portion 31 First wedge prism 32 Second wedge prism 33 First magnet 34 Second magnet 35 First frame 41 Peripheral wall portion 42 Annular portion 100, 200 Optical communication device 110 Light emitting element 130 Lens 210 Main body 220 Mount CA Rotation axis G1, G2 Center of gravity LB Light beam

Claims (7)

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. 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: The optical axis adjustment device described in claim 2, wherein the coil has a fan-shaped configuration that spreads outward from the rotation axis when viewed in a plane. 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. The optical axis adjusting device according to claim 1 , further comprising a pair of the wedge prisms. 5. The optical axis adjusting device according to claim 1 , comprising two or more pairs of the wedge prisms. An optical communication device comprising the optical axis adjusting device according to any one of claims 1 to 6 .