Optical communication optical system and optical communication device

Abstract

To make it possible to simply prevent vibration of signal light in an optical communication optical system including wedge prisms.SOLUTION: An optical communication optical system has four groups, i.e., a first group (11) to a fourth group (14). The optical communication optical system satisfies a first relation based on focal lengths of the first group (11) and the second group (12), and a second relation based on rotation angles and apex angles of two wedge prisms that rotate in opposite directions at the same angle, in each of two pairs of wedge prisms in the third group (13).SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, radio wave communication technologies such as 5G have dramatically increased in speed. In the field of communication technologies, there is a demand to respond to such increases in speed. Regarding high-speed communication, optical wireless communication (also called "optical communication") is currently attracting attention. Optical wireless communication is particularly suited to communication between fixed locations, such as base stations and relay points. As such optical communication technology, a beam expander is known that expands the beam diameter of parallel light (collimated light) while maintaining the parallel light by using an optical system with a short overall lens length (see, for example, Patent Document 1).

[0003] On the other hand, optical wireless communication requires vibration isolation technology to prevent vibration of the optical communication device itself in which the optical communication optical system is installed. The technology described in Patent Document 1 leaves room for further study from the viewpoint of vibration isolation of the optical communication device.

[0004] As an anti-vibration technique for optical wireless communication, a technique of mounting an optical system on a mount such as a gimbal mechanism is generally known. However, the gimbal mechanism may not be able to sufficiently prevent even minute vibrations. As a result, the optical axis may shift during communication due to the vibration, which may cause communication failure in receiving the optical wireless communication.

[0005] As a vibration isolation technique for optical wireless communication, a technique using a fine pointing mirror driven by a MEMS (microelectromechanical system) is generally known. However, the fine pointing mirror is expensive and its small size makes it very difficult to arrange it according to the size of the beam diameter, so there is room for further study.

[0006] As an optical wireless communication technology that solves the above-mentioned problems of vibration reduction, size, cost, etc., an image stabilization device is known that can perform image stabilization by the optical path deflection action of a wedge prism, while suppressing increases in the optical path length and costs (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-362608 [Patent Document 2] JP 2008-209712 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the technology described in Patent Document 2, a convex or concave lens is attached to one of the wedge prisms. This increases the weight of the wedge prism, which is disadvantageous in controlling the rotation of the wedge prism. In addition, since a lens is attached to the wedge prism, the location where the wedge prism can be placed in the optical system is limited. Furthermore, since a lens is attached to the wedge prism, the eccentricity of the lens itself is added to the rotation control of the wedge prism, and the correction of the wedge prism during vibration compensation (the rotation angle that corrects the angle of incidence) becomes large, making control difficult.

[0009] An object of one aspect of the present invention is to provide a technique capable of simply preventing vibration of signal light in an optical communication system including a wedge prism. [Means for solving the problem]

[0010] In order to solve the above problems, an optical communication optical system according to one aspect of the present invention is an optical communication optical system arranged on an optical path of a signal light emitted from a light-emitting element and transmitted, or a signal light incident on a light-receiving element and received, a first group, a second group, a third group, and a fourth group arranged in this order from the opposite side to the light emitting element or the light receiving element, the first group changes a beam diameter of the signal light so as to be smaller at an end of the first group on the second group side in an optical axis direction; the second group changes a beam diameter of the signal light so as to be smaller at an end of the second group on the third group side in the optical axis direction; the third group is composed of two pairs of wedge prisms, each pair of wedge prisms being composed of two wedge prisms that rotate in opposite directions to each other and at the same rotation angle; the fourth group changes a beam diameter of the signal so as to be smaller at an end of the fourth group on the side of the light emitting element or the light receiving element in the optical axis direction; The following formulas (1) and (2) are satisfied. 3.89 <Ff / Bf<14.00···(1) 0.090 <R / a<6.565···(2) (In formula (1), Ff represents the focal length (mm) of the first group, Bf represents the focal length (mm) of the second group, and in formula (2), R represents the rotation angle of the wedge prism in one or the other of the wedge prism pairs, and a represents the apex angle of the wedge prism in one or the other of the wedge prism pairs).

[0011] In order to solve the above problem, an optical communication device according to an aspect of the present invention includes the above optical communication optical system. Effect of the Invention

[0012] According to one aspect of the present invention, it is possible to easily prevent vibration of signal light in an optical communication system including a wedge prism. [Brief description of the drawings]

[0013] [Figure 1] 1 is a diagram illustrating a schematic configuration of an optical communication device according to an embodiment of the present invention. [Diagram 2] FIG. 11 is a perspective view showing an arrangement of wedge prisms in a third group in one embodiment of the present invention. [Diagram 3] FIG. 11 is a front view illustrating an arrangement of wedge prisms in a third group in one embodiment of the present invention. [Figure 4] FIG. 11 is a plan view illustrating an arrangement of wedge prisms in a third group in one embodiment of the present invention. [Diagram 5] FIG. 4 is a diagram illustrating a drive mechanism for a wedge prism pair in one embodiment of the present invention. [Figure 6] 1 is a front view showing a schematic configuration of an optical communication optical system according to a first embodiment. [Figure 7] 4 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system in Example 1 in which the wedge prism is removed. FIG. [Figure 8] 4 is a diagram showing the wavelength dependency of the focus shift amount in the optical communication optical system of Example 1 at wavelengths of 1530 nm to 1565 nm. [Figure 9] FIG. 11 is a front view showing a schematic configuration of an optical communication system according to a second embodiment. [Figure 10] 10 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 2 in which the wedge prism is removed. FIG. [Figure 11] FIG. 11 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 2. [Figure 12] FIG. 11 is a front view showing a schematic configuration of an optical communication system according to a third embodiment. [Figure 13] 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 3 in which the wedge prism is removed. FIG. [Figure 14] FIG. 11 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 3. [Figure 15] FIG. 11 is a front view showing a schematic configuration of an optical communication system according to a fourth embodiment. [Figure 16] 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 4 in which the wedge prism is removed. FIG. [Figure 17]FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 4. [Figure 18] FIG. 13 is a front view showing a schematic configuration of an optical communication system according to a fifth embodiment. [Figure 19] 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 5 in which the wedge prism is removed. FIG. [Figure 20] FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 5. [Figure 21] FIG. 13 is a front view showing a schematic configuration of an optical communication system according to a sixth embodiment. [Figure 22] 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 6 in which the wedge prism is removed. FIG. [Diagram 23] FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 6. [Figure 24] FIG. 13 is a front view illustrating a schematic configuration of an optical communication system according to a seventh embodiment. [Diagram 25] FIG. 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 7 in which the wedge prism is removed. [Figure 26] FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 7. [Figure 27] FIG. 13 is a front view showing a schematic configuration of an optical communication system according to an eighth embodiment. [Figure 28] 13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 8 in which the wedge prism is removed. FIG. [Figure 29] FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 8. [Diagram 30] FIG. 13 is a front view showing a schematic configuration of an optical communication system according to a ninth embodiment. [Diagram 31]13 is a diagram showing spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 9 in which the wedge prism is removed. FIG. [Diagram 32] FIG. 13 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 9. [Diagram 33] FIG. 23 is a front view showing a schematic configuration of an optical communication system according to a tenth embodiment. [Diagram 34] 13 is a diagram illustrating spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 10 in which the wedge prism is removed. FIG. [Diagram 35] FIG. 23 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 10. [Diagram 36] FIG. 23 is a front view showing a schematic configuration of the optical communication system according to the eleventh embodiment. [Figure 37] FIG. 21 is a diagram illustrating spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 11 in which the wedge prism is removed. [Figure 38] FIG. 23 is a diagram showing the wavelength dependency of the focus shift amount in the wavelength range of 1530 nm to 1565 nm in the optical communication optical system of Example 11. [Figure 39] FIG. 23 is a front view showing a schematic configuration of an optical communication system according to a twelfth embodiment. [Diagram 40] FIG. 23 is a diagram illustrating spherical aberration of light with a wavelength of 1550 nm in the optical communication optical system of Example 12 in which the wedge prism is removed. [Diagram 41] FIG. 23 is a diagram showing the wavelength dependency of the focus shift amount in the optical communication optical system of Example 12 at wavelengths of 1530 nm to 1565 nm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] An embodiment of the present invention will be described in detail below. This embodiment is provided with a function of correcting, with a less expensive configuration, an optical core caused by angular deviation of the signal light generated by vibrations of an optical communication device that includes the optical system for transmitting or receiving signal light in optical communication applications.

[0015] [Optical communication optical system] [Optical configuration] An optical communication optical system according to one embodiment of the present invention is disposed on the optical path of a signal light emitted from a light-emitting element and transmitted, or a signal light incident on a light-receiving element and received. In this manner, the optical communication optical system according to this embodiment is disposed in combination with a light-emitting element that emits a signal light passing through the optical system, or a light-receiving element into which the signal light passing through the optical system is incident.

[0016] The optical communication system of this embodiment includes a first group, a second group, a third group, and a fourth group arranged in this order from the opposite side to the light emitting element or the light receiving element. Each group is fixed to a specific position in the optical axis direction determined from the viewpoint of realizing a desired function. Each group may be fixed so as to be appropriately positioned in the optical axis direction from the viewpoint of versatility, etc.

[0017] The first group, the second group, and the fourth group are groups of optical elements including a lens. Examples of lenses include a single lens, a cemented lens, and a compound lens. Examples of single lenses include a spherical lens and an aspherical lens. It is preferable that at least one of the first group, the second group, and the fourth group includes an aspherical lens from the viewpoint of suppressing aberration in the optical communication optical system and suppressing changes in beam diameter and spot shape during vibration prevention by improving the focusing performance of the entire optical system. The effect of including an aspherical lens tends to be more pronounced as the lens diameter becomes larger. From this viewpoint, it is more preferable that the first group or the second group includes an aspherical lens, and it is even more preferable that the first group includes an aspherical lens.

[0018] The third group is composed of a pair of wedge prisms. The optical configuration of the third group will be described in detail later.

[0019] The first to fourth groups may further include optical elements other than a lens or a wedge prism as long as the effects of this embodiment can be obtained. Examples of the optical elements include a plane-parallel plate, a mirror, a filter, and a beam splitter.

[0020] <First group> The first group is designed to change the beam diameter of the signal light to be smaller at the end on the second group side in the optical axis direction. If the direction from the fourth group toward the first group in the optical axis direction of the optical communication optical system is the outward direction, and the direction from the first group toward the fourth group is the inward direction, the signal light outside the first group is the signal light propagating between optical communication devices in optical communication, for example, collimated light with a larger beam diameter. The signal light inside the first group may be collimated light with a smaller beam diameter, may be converging light with a gradually decreasing beam diameter, or may be converging-diverging light with a gradually decreasing beam diameter that converges and then expands.

[0021] <Second group> The second group is designed to change the beam diameter of the signal light so that it becomes smaller at the end on the third group side in the optical axis direction. The signal light inside the second group may be collimated light with a smaller beam diameter, or may be convergent light, or may be convergent-divergent light. From the viewpoint of keeping the cross-sectional shape (also called "spot shape") of the signal light beam constant when passing through the wedge prism in the third group and suppressing deterioration of communication performance due to changes in the spot shape of the signal light, it is preferable that the signal light inside the second group is collimated light.

[0022] In optical communication, the signal light propagating between optical communication devices is usually collimated light. From this viewpoint, the first group can be said to be a lens group that transmits or receives collimated light having the largest beam diameter among the collimated light in the optical communication device to the outside. Also, from the viewpoint of the accuracy of the optical communication as described above, it is preferable that the signal light propagating between the second group and the third group is collimated light. From this viewpoint, the second group can be said to be a lens group that transmits or receives collimated light having the smallest beam diameter among the collimated light in the optical communication device to the inside. Thus, the first group and the second group can function as a beam expander that expands the beam diameter of the collimated light from the inside to the outside. In this way, the first group and the second group may be a lens group that functions as the beam expander together.

[0023] In a beam expander optical system having a first group forming the maximum collimated light and a second group forming the minimum collimated light at a sufficient distance from the first group, if the optical system is a Galilean type in which convergent light from the first group enters the second group and becomes the minimum collimated light in the second group, it is preferable from the viewpoint of reducing the number of lenses and simplifying the optical configuration of the first group and the second group (to reduce the beam diameter of the collimated light). If the optical system is a Keplerian type in which convergent light from the first group forms a primary image between the first group forming the maximum collimated light and the second group, diverges again and enters the second group and becomes the minimum collimated light in the second group, it is preferable from the viewpoint of suppressing the occurrence of aberration. Note that it is preferable that the sufficient distance between the first group and the second group is the maximum interval among the intervals between the lenses arranged from the object side of the first group to the image side of the second group, from the viewpoint of facilitating control of the ratio between the maximum collimated diameter forming the first group and the minimum collimated diameter of the second group, and from the viewpoint of reducing the aberration occurring due to the ratio of the diameters.

[0024] <Group 3> The third group is made up of two wedge prism pairs, each of which consists of two wedge prisms that rotate in opposite directions with the same rotation angle.

[0025] In each wedge prism pair, the two wedge prisms are arranged such that the inclined surfaces of one face the other without contacting each other, and the apex angles of one face the other are located on opposite sides of the optical axis. The positions of both wedge prisms when the major axes on the inclined surfaces of each wedge prism in the wedge prism pair overlap with each other in the optical axis direction are defined as the positions where the wedge prisms directly face each other, and are also called the reference position.

[0026] In the third group, the two wedge prism pairs are arranged so that when all the wedge prisms are in the reference position, the long axis of one wedge prism pair and the long axis of the other wedge prism pair cross each other, preferably perpendicularly, when viewed along the optical axis. By arranging in this way, it is possible to eliminate the vibration of the signal light in a planar direction perpendicular to the optical axis. Arranging the long axes of the two wedge prism pairs so that they are perpendicular is preferable from the viewpoint of minimizing the rotation angle of each wedge prism in vibration isolation and improving the accuracy and performance of vibration isolation against the vibration of the signal light. For example, the two wedge prism pairs each perform vibration isolation correction in the X direction and the Y direction.

[0027] The larger the apex angle of the wedge prism, the higher the sensitivity of the deflection of the signal light, and therefore the more precise control of the rotational motion of the wedge prism is required. The apex angle of the wedge prism may be appropriately determined from the viewpoints of the fineness of the vibration of the signal light and the precision of the control.

[0028] The drive device for rotating the wedge prism can be a known drive device within a range that allows the wedge prism to rotate so as to accommodate minute vibration damping of the signal light. A voice coil motor can be suitably used as the drive device from the viewpoint of realizing high-speed rotational drive and control of the rotation angle.

[0029] <Group 4> The fourth group is designed to change the beam diameter of the signal light so that it becomes smaller at the end on the light emitting element or light receiving element side in the optical axis direction. The signal light outside the fourth group (on the third group side) may be collimated light with a larger beam diameter, divergent light whose beam diameter expands toward the outside, or convergent divergent light. As with the second group, from the viewpoint of keeping the cross-sectional shape of the signal light beam constant when passing through the wedge prism in the third group and suppressing deterioration of communication performance due to changes in the cross-sectional shape, it is preferable that the signal light outside the fourth group is collimated light.

[0030] The signal light inside the fourth group may be collimated light with a smaller beam diameter, may be convergent light, or may be convergent-divergent light, depending on the configuration inside. For example, when the light-emitting element or the light-receiving element is directly disposed inside the fourth group, or when the fourth group and the light-emitting element are optically connected via an optical fiber, the signal light may be any of the above. When the fourth group and the light-receiving element are optically connected via an optical fiber, the signal light may be convergent light. From the viewpoint of versatility applicable to both the transmitting device and the receiving device of the optical communication device, it is preferable that the fourth group is designed so that the signal light on the inside is convergent light.

[0031] <Other configurations> The optical communication optical system of this embodiment may further include other configurations other than the first group to the fourth group described above, within a range in which the effects of this embodiment can be obtained. Examples of other configurations include a position adjustment device. The position adjustment device may be configured by a detection unit that detects the difference between the actual position of the signal light and its reference position, and a control unit that controls the rotation of the wedge prism so that the difference detected by the detection unit becomes small. The reference position of the signal light is, for example, the position of the signal light when the center of the shape of the signal light (also called a "spot shape", usually a circle) on a plane perpendicular to the optical axis of the signal light is the optical axis. The signal light detected by the position adjustment device is preferably a collimated signal light from the viewpoint of increasing the detection accuracy of the position of the signal light relative to the optical axis, and is preferably a signal light with a smaller beam diameter from the viewpoint. From this viewpoint, it is preferable that the signal light detected by the position adjustment device is a signal light between the second group and the third group, or between the third group and the fourth group.

[0032] <Beam diameter> In the optical communication system of this embodiment, the smaller the beam diameter of the signal light is, the higher the power density of the signal light is, and the higher the sensitivity of the deflection of the signal light by the wedge prism is. The beam diameter of the signal light between the second group and the fourth group in the optical communication system may be appropriately determined from the viewpoints of the power density and the sensitivity.

[0033] [Expression expressing the condition] The optical communication system of this embodiment employs the above-mentioned configuration and preferably satisfies at least one of the following expressions.

[0034] <Formula (1)> 3.89 <Ff / Bf<14.00···(1) Here, "Ff" represents the focal length (mm) of the first group, and "Bf" represents the focal length (mm) of the second group. "Focal length of the first group" means: is the focal length of the lens group that forms the maximum collimated light, and "the focal length of the second group" is the focal length of the lens group that forms the minimum collimated light. In this embodiment, formula (1) is satisfied whether the first and second groups form a Galilean or Keplerian optical system.

[0035] When Ff / Bf is below the lower limit of formula (1), the rotation angle of the wedge prism during vibration compensation becomes too small, and the resolution of the rotation angle increases, which may result in insufficient rotation stopping accuracy during compensation. When Ff / Bf is above the upper limit of formula (1), the rotation angle of the wedge prism during vibration compensation becomes too large, and the rotation during vibration compensation becomes slow, which may result in a long correction time. From the viewpoint of obtaining an appropriate rotation resolution, Ff / Bf is more preferably 5.2 or more, and even more preferably 6.5 or more. Also, from the viewpoint of specifying an appropriate correction time during vibration compensation, Ff / Bf is more preferably 7.8 or less, and even more preferably 6.5 or less.

[0036] <Formula (2)> 0.090 <R / a<6.565···(2) where "R" represents the rotation angle of the wedge prism in one or the other wedge prism pair, and "a" represents the apex angle of the wedge prism in one or the other wedge prism pair. Thus, R and a in equation (2) define the relationship between the rotation angle and apex angle of the wedge prism in each wedge prism pair, respectively.

[0037] If the rotation angle of the wedge prism in one of the two wedge prism pairs in the third group is R1 and the apex angle is a1, and the rotation angle of the wedge prism in the other wedge prism pair is R2 and the apex angle is a2, then formula (2) can be expressed by the following formulas (2-1) and (2-2). In the following explanation, R is a general term for R1 and R2 and represents one or both of them. Similarly, a is a general term for a1 and a2 and represents one or both of them. 0.090 <R1 / a1<6.565···(2-1) 0.090 <R2 / a2<6.565···(2-2)

[0038] When R / a is below the lower limit of formula (2), the apex angle of the wedge prism becomes large, and the spot shape of the signal light may become elliptical and large. Also, when R / a is below the lower limit of formula (2), the rotation angle of the wedge prism becomes small, and the resolution of the rotation of the wedge prism decreases, and the accuracy of vibration isolation of the signal light may decrease. When R / a is above the upper limit of formula (2), the rotation angle of the wedge prism becomes large, and the rotation speed of the wedge prism becomes slow, and the fast vibration of the signal light may not be tracked. From the viewpoint of improving the accuracy of vibration isolation of the signal light, R / a is more preferably 0.129 or more, and even more preferably 0.72 or more. Also, from the viewpoint of improving the accuracy of vibration isolation of the signal light, R / a is more preferably 1.046 or less, and even more preferably 1.57 or less.

[0039] <Formula (3)> |C1-C2|≦14.715 (3) Here, "C1" represents the amount of movement (μm) of the focal position of signal light with a wavelength of 1530 nm when the focal position of signal light with a wavelength of 1550 nm is used as the reference, and "C2" represents the amount of movement (μm) of the focal position of signal light with a wavelength of 1565 nm when the focal position of signal light with a wavelength of 1550 nm is used as the reference.

[0040] Equation (3) defines the axial chromatic aberration of the optical communication system. More specifically, Equation (3) defines the difference in the size of the spot shape of the signal light due to chromatic aberration when switching to any wavelength in the C-band in optical communication.

[0041] If |C1-C2| is greater than 14.715, the focus of signal light of wavelengths other than the C-band relative to the signal light of wavelength 1550 nm may shift, the spot diameter of the signal light may increase, and communication performance in optical communication may deteriorate. From the viewpoint of improving communication performance, it is more preferable that |C1-C2| is 2.0 or less. From the viewpoint of communication performance, the smaller |C1-C2| is, the better, and it may be 0 or more.

[0042] <Formula (4)> 1.4 <n<1.674···(4) Here, "n" represents the refractive index of light with a wavelength of 1550 nm in the material of the wedge prism. "n" may be the same for all wedge prisms, may be different for each wedge prism pair, or may be different for each wedge prism. Equation (4) specifies the glass material of the wedge prism.

[0043] If n is 1.674 or less, the rotation angle of the wedge prism becomes small, the resolution of the rotation of the wedge prism decreases, and the accuracy of vibration isolation of the signal light may decrease. From the viewpoint of improving the accuracy of vibration isolation of the signal light, n is more preferably 1.5 or less, and even more preferably 1.46 or less. From the viewpoint of the optical axis deviation during vibration isolation correction, n may be 1.5 or more, or may be 1.6 or more. The most preferable range is 1.4 or more and 1.45 or less.

[0044] [Optical communication device] Next, an optical communication device according to an embodiment of the present invention will be described. FIG. 1 is a diagram showing a schematic configuration of an optical communication device according to an embodiment of the present invention. As shown in FIG. 1, the optical communication device 1 has a casing 10 and an optical fiber 20. The casing 10 is a long and narrow rectangular housing, and has an opening at one end through which signal light passes, and the optical fiber 20 is inserted at the other end. In the figure, the Z direction is the direction along the optical axis OA. The side indicated by the arrow of the Z axis is the inside as described above, and the opposite side is the outside. The Y direction and the X direction are perpendicular to each other and perpendicular to the Z direction, respectively.

[0045] The optical fiber 20 includes a single mode fiber 21 and a connector 22. The connector 22 is optically connected to a light emitting element that emits a signal light or a light receiving element to which the signal light is incident. The light emitting element may be an element that converts electricity into light, such as a light emitting diode or a semiconductor laser. The light receiving element may be an element that receives a signal light in optical communication and converts it into an electrical signal, such as a photodiode or a CMOS (complementary metal oxide semiconductor) image sensor. The connector 22 may be connected to a further optical fiber.

[0046] An optical communication system is arranged in the casing 10. The optical communication system includes a first group 11, a second group 12, a third group 13, and a fourth group 14. These are arranged in the above order from the opposite side to the optical fiber 20 connected to the light emitting element or the light receiving element. The optical communication system further includes a beam splitter 31 that splits a part of the signal light from the third group 13 in the optical path of the signal light between the third group 13 and the fourth group 14, and a split type photodiode 32 into which the signal light split from the beam splitter 31 is incident. The split type photodiode 32 has four detection parts divided into four by an X axis corresponding to the X direction and a Y axis corresponding to the Y direction, and is configured so that each of the intensities Q1 to Q4 detected by each detection part is input to a control unit 33.

[0047] When the light-emitting element is connected to the optical fiber 20, the signal light passing through the group is also called "transmitted light," and when the light-receiving element is connected to the optical fiber 20, the signal light passing through the group is also called "received light." "Signal light" is a general term for transmitted light and received light, and means either or both of them.

[0048] In this embodiment, the first group 11 transmits or receives collimated light from the end on the opening side of the casing 10, and transmits or receives signal light whose beam diameter gradually decreases toward the second group 12 from the end on the second group 12 side. The second group 12 transmits or receives signal light whose beam diameter gradually decreases toward the second group 12 at the end on the first group 11 side, and transmits or receives signal light which is collimated light toward the third group 13 at the end on the third group 13 side. The fourth group 14 transmits or receives signal light which is collimated light at the end on the third group 13 side, and transmits or receives signal light whose beam diameter gradually decreases toward the core of the optical fiber 20 at the end on the optical fiber 20 side.

[0049] Fig. 2 is a perspective view showing a schematic arrangement of wedge prisms in the third group 13 in this embodiment. As shown in Fig. 2, the third group 13 is composed of two wedge prism pairs 131 and 132. In this embodiment, the wedge prism pair 131 is arranged on the second group 12 side, and the wedge prism pair 132 is arranged on the fourth group side.

[0050] Each wedge prism pair is composed of two wedge prisms. Fig. 3 is a front view showing the arrangement of the wedge prisms in the third group in this embodiment, and Fig. 4 is a plan view showing the arrangement of the wedge prisms in the third group in this embodiment. As shown in Figs. 3 and 4, the wedge prism pair 131 is composed of two wedge prisms 41 and 42, and the wedge prism pair 132 is composed of two wedge prisms 43 and 44.

[0051] As shown in Fig. 3, a wedge prism (e.g., reference numeral 44) has a cylindrical shape with one end face formed at an angle, with one end face perpendicular to the optical axis and the other end face oblique to the optical axis (at an angle with respect to the perpendicular plane). The angle that the other end face makes with respect to the plane perpendicular to the optical axis (the angle indicated by the curved arrow in Fig. 3) is the apex angle of the wedge prism.

[0052] In addition, when one of the wedge prisms in a wedge prism pair rotates forward, the other rotates backward. For example, in the case of wedge prism pair 131, when wedge prism 41 rotates clockwise, wedge prism 42 rotates counterclockwise, as shown by the solid curved arrow in Figure 2, and when wedge prism 41 rotates counterclockwise, wedge prism 42 rotates clockwise, as shown by the dashed curved arrow.

[0053] In the initial state, the apex angle of wedge prism 41 is located on one side of the X-axis, and the apex angle of wedge prism 42 is located on the other side of the X-axis. In addition, in the initial state, the apex angle of wedge prism 43 is located on one side of the Y-axis, and the apex angle of wedge prism 44 is located on the other side of the Y-axis. In this way, when the line connecting the apex angle and the center of the wedge prism is set as the axis of the wedge prism, the two wedge prisms are installed so that their axes overlap and their apex angles are symmetrical with respect to the center when viewed along the optical axis OA. Then, each wedge prism pair is installed so that the axis of the wedge prism in one wedge prism pair is perpendicular to the axis of the wedge prism in the other wedge prism pair.

[0054] Each wedge prism pair is composed of two wedge prisms that rotate in opposite directions and at the same rotation angle. Figure 5 is a schematic diagram showing the drive mechanism for the wedge prism pair in this embodiment. Figure 5 shows the drive mechanism for the wedge prism pair 131, but the wedge prism pair 132 has a similar configuration.

[0055] 5, the driving mechanism includes a first coil 412 arranged on annular substrate 34, a first hall element 413 arranged inside the first coil 412, and a second coil 422 and a second hall element 423 arranged inside the first coil 412. First coil 412 and second coil 422 are arranged in four-fold symmetrical positions (positions shifted by 90°) when viewed from above, and each coil is made of a conducting wire wound in a substantially fan-shaped shape when viewed from above.

[0056] The drive mechanism also has a first magnet 411 arranged in a position corresponding to the first coil 412 in a plan view and corresponding to the wedge prism 41 (for example, on the frame of the wedge prism 41), and a second magnet 421 arranged in a position corresponding to the second coil 422 in a plan view and corresponding to the wedge prism 42 (for example, on the frame of the wedge prism 42). The control unit 33 described above is also arranged on the substrate 34.

[0057] The coils and magnets described above constitute a voice coil motor that rotates the wedge prism by energizing the coils. When the first coil 412 is energized, the wedge prism 41 rotates, for example, in a clockwise direction, and when the second coil 422 is energized, the wedge prism 42 rotates, for example, in a counterclockwise direction. The first coil 412 and the second coil 422 are supplied with currents of substantially the same amount at the same time, and the wedge prism 41 and the wedge prism 42 rotate in opposite directions at substantially the same rotation angle.

[0058] Hereinafter, the rotational movement of the wedge prism will be specifically described using the wedge prism 41 as an example. In this embodiment, the other wedge prisms also perform rotational movement in the same manner as the wedge prism 41, but the description of the rotational movement of the other wedge prisms will not be repeated.

[0059] When a current is applied to the first coil 412, the first hall element 413 detects a voltage corresponding to the magnetic field (magnetic flux density). The rotation angle of the wedge prism 41 can be approximated by a linear expression in a specific range with the voltage value (magnetic flux density) detected by the first hall element 413. The control unit 33 obtains the current rotation angle of the wedge prism 41 based on such a correlation. The control unit 33 controls the rotation of the wedge prism 41 by the voice coil motor according to the obtained current angle, and rotates the wedge prism 41 to the target rotation angle.

[0060] The target rotation angle can be obtained, for example, as follows. The control unit 33 obtains output values ​​Q1 to Q4 of the segmented photodiode 32. The control unit 33 also obtains the displacement amounts in the X-axis and Y-axis directions of the signal light according to the obtained output values ​​Q1 to Q4. For example, the displacement amount Δx in the X-axis direction and the displacement amount Δy in the Y-axis direction can be calculated from the following equations. Δx=(Q1+Q3)-(Q2+Q4) Δy=(Q1+Q2)-(Q3+Q4)

[0061] Next, the control unit 33 acquires, for example, a rotation angle θx of the wedge prisms 41, 42 corresponding to the X-axis and a rotation angle θy of the wedge prisms 43, 44 corresponding to the Y-axis from Δx and Δy in the split photodiode 32 based on the correlation between the position of the signal light in the light receiving unit 200 and the position of the branched light in the split photodiode 32. θx is the difference between Ax, which is the rotation angle of the wedge prisms 41, 42 when the receiving position of the signal light is the center position of the split photodiode 32 (for example, 0 degrees, initial position or reference position), and Bx, which is a correction rotation angle for correcting the blur of the signal light and is, for example, a target value in PID control. θy is the difference between Ay, which is the rotation angle of the wedge prisms 43, 44 in the reference position (for example, 0 degrees), and By, which is the correction rotation angle.

[0062] The control unit 33 repeatedly executes the above control during optical communication. Even if the signal light vibrates finely at high speed, when the signal light deviates from the reference direction or position, the wedge prisms 41, 42 and 43, 44 rotate to a rotation angle that eliminates the deviation. Such control processing and the rotation of the wedge prisms are performed at a sufficiently high speed. Therefore, the optical system for optical communication in this embodiment can eliminate the influence of fine vibrations of the signal light on optical communication.

[0063] [Variations] In the present invention, in the above embodiment, the optical fiber 20 may be replaced with the above-mentioned light emitting element or light receiving element.

[0064] The target rotation angle of the wedge prism may be obtained based on the detection value of another sensor capable of detecting vibration of the optical communication system. For example, the attitude of the casing 10 may be detected by the detection value of an acceleration sensor such as a gyro sensor arranged in the casing 10, and the control unit 33 may obtain the target rotation angle of each wedge prism based on the detection value. This embodiment does not need to include the beam splitter 31 and the split photodiode 32, and can be substantially configured only by the four optical systems of the first to fourth groups, and can obtain the target rotation angle regardless of whether the signal light is a transmission light or a reception light.

[0065] Alternatively, the optical communication device may further include an additional beam splitter that splits a part of the signal light from the fourth group 14 to the third group 13, and a mirror that guides the split signal light to the split photodiode 32. With this configuration, it is possible to obtain the target rotation angle of each wedge prism from the output value of the split photodiode 32 for both the transmitted light and the received light.

[0066] The arrangement of the four wedge prisms in the direction of the optical axis OA is not limited. For example, the wedge prisms 41 and 42 constituting the wedge prism pair 131 and the wedge prisms 43 and 44 constituting the wedge prism pair 132 may be arranged in the order of "41, 43, 42, 44" or "41, 43, 44, 42."

[0067] The apex angle a of the wedge prisms 41, 42 in the wedge prism pair 131 and the apex angle b of the wedge prisms 43, 44 in the wedge prism pair 132 may be the same as or different from each other. For example, when vibration in one direction in a plane perpendicular to the optical axis is more significant than vibration in other directions, the apex angle of the wedge prism corresponding to that one direction may be made larger to increase the sensitivity of the deflection of the signal light in that one direction.

[0068] 〔summary〕 A first aspect of the present invention is an optical communication optical system arranged on the optical path of signal light emitted from a light-emitting element and transmitted, or signal light incident on a light-receiving element and received, and includes a first group (11), a second group (12), a third group (13), and a fourth group (14) arranged in this order from the opposite side to the light-emitting element or the light-receiving element, wherein the first group changes the beam diameter of the signal light to be smaller at the end on the second group side in the optical axis direction, the second group changes the beam diameter of the signal light to be smaller at the end on the third group side in the optical axis direction, the third group is composed of two wedge prism pairs (131, 132), and the wedge prism pairs are composed of two wedge prisms (41, 42 or 43, 44) that rotate in opposite directions to each other and at the same rotation angle, and the fourth group changes the beam diameter of the signal to be smaller at the end on the light-emitting element or the light-receiving element side in the optical axis direction, and satisfies the following equations (1) and (2). In equation (1), Ff represents the focal length (mm) of the first group, Bf represents the focal length (mm) of the second group, and in equation (2), R represents the rotation angle of the wedge prism in one or the other wedge prism pair, and a represents the apex angle of the wedge prism in one or the other wedge prism pair. 3.89 <Ff / Bf<14.00···(1) 0.090 < R / a < 6.565 ··· (2)

[0069] According to the first aspect, in an optical communication optical system including a wedge prism, vibration of the signal light can be easily prevented.

[0070] The second aspect of the present invention satisfies the formula (3) in the first aspect. In the formula (3), C1 represents the amount of movement (μm) of the focal position of the signal light with a wavelength of 1530 nm with respect to the focal position of the signal light with a wavelength of 1550 nm, and C2 represents the amount of movement (μm) of the focal position of the signal light with a wavelength of 1565 nm with respect to the focal position of the signal light with a wavelength of 1550 nm. |C1 - C2| ≤ 14.715 ··· (3)

[0071] The second aspect is more effective from the viewpoint of enhancing the communication performance of optical communication in the C band region.

[0072] The third aspect of the present invention satisfies the formula (4) in the first aspect or the second aspect. In the formula (4), n represents the refractive index of light with a wavelength of 1550 nm in the material of the wedge prism. 1.4 < n < 1.674 ··· Formula (4)

[0073] The third aspect is more effective from the viewpoint of enhancing the accuracy of vibration prevention of the signal light.

[0074] The fourth aspect of the present invention changes the beam diameter of the signal light in any one of the first aspect to the third aspect so that the signal light between the second group and the fourth group becomes collimated light. The fourth aspect is more effective from the viewpoint of suppressing a decrease in communication performance due to a change in the spot shape of the signal light.

[0075] The fifth aspect of the present invention is such that in any one of the first aspect to the fourth aspect, at least one of the first group, the second group, and the fourth group includes an aspherical lens. The fifth aspect is more effective from the viewpoint of suppressing changes in the beam diameter and spot shape of the signal light during vibration prevention.

[0076] A sixth aspect of the present invention is an optical communication device including the optical communication system according to any one of the first to fifth aspects. According to the sixth aspect, it is possible to easily prevent vibration of signal light in the optical communication optical system including a wedge prism.

[0077] Recent radio wave communication technology has reached its theoretical limit, and methods such as increasing the number of bands or increasing the frequency are considered for further speed increase. However, radio wave bands are in short supply internationally, making it difficult to increase the number of bands. In addition, increasing the frequency increases the directivity of radio waves, making it difficult for diffraction, which is an advantage of radio waves, to occur, and radio waves cannot bend around buildings or in the shadows of buildings, making it impossible to ensure communication quality. This requires new measures such as moving or expanding base stations. Wired communication is also difficult due to the cost of installation and the problem of wiring.

[0078] On the other hand, optical communication has the advantage in terms of security because, although the signal light has a high degree of directivity, it does not propagate over a wide area like radio waves. Also, although light is an electromagnetic wave just like the radio waves used in communication, anyone can use it freely without being bound by the Radio Law.

[0079] Optical communication is generally considered to be disadvantageous for communication from or between moving objects. However, optical communication is considered to be advantageous as a technology that complements radio wave communication in space communication between artificial satellites, and research in this field is being conducted. In the future, it is expected that more precise optical technology will be required as the speed and distance of optical wireless communication increases.

[0080] The optical communication device and optical communication system of the present invention can achieve vibration isolation of signal light in optical communication in the C-band with a simple configuration. The present invention, which has such effects, is expected to contribute to the achievement of Goal 9 "Build resilient infrastructure, promote inclusive and sustainable industrialization and promote innovation" of the Sustainable Development Goals (SDGs) advocated by the United Nations, which includes the development of resilient infrastructure.

[0081] 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 the different embodiments are also included in the technical scope of the present invention. EXAMPLES

[0082] In the following examples, the type in the table is expressed as "SPH" for spherical lenses and "ASP" for aspherical lenses. "R" is the radius of curvature, "D" is the lens thickness or lens spacing, "n1530" is the refractive index at a wavelength of 1530 nm, "n1550" is the refractive index at a wavelength of 1550 nm, and "n1565" is the refractive index at a wavelength of 1565 nm.

[0083] The aspheric surface (ASP) even-order aspheric coefficient z is defined by the following formula, where "c" is the curvature (1 / r), "h" is the height from the optical axis, "K" is the conic coefficient, and "A4", "A6", "A8", and "A10" are the aspheric coefficients of each order. [formula] z=ch 2 / [1+{1-(1+K)c 2 h 2} 1 / 2 ]+A4h 4 +A6h 6 +A8h 8 +A10h 10

[0084] In the following tables, all length units except for wavelength are in "mm." Also, "Ea" is "×10 -a ".

[0085] Example 1 Hereinafter, an embodiment of the optical communication optical system of the present invention will be described with reference to the drawings. FIG. 6 is a front view showing a schematic configuration of the optical communication optical system of the first embodiment, FIG. 7 is a spherical aberration diagram of the optical communication optical system of the first embodiment except for the wedge prism at a wavelength of 1550 nm, and FIG. 8 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication optical system of the first embodiment. Table 1 shows the numerical data of the optical communication optical system, and Table 2 shows the numerical data of the aspheric coefficients. Table 3 shows the rotation angle for each apex angle of the wedge prism for vibration correction of a vibration angle of 100 mrad, and the numerical data of formula (2) at that time. In this embodiment and the following embodiments, all the wedge prisms arranged in the optical system have the same apex angle and rotate at the same rotation angle (absolute value). In Table 1, surface numbers 1 to 10 represent the first group, surface numbers 11 to 14 represent the second group, surface numbers 15 to 22 represent the third group, and surface numbers 23 to 29 represent the fourth group. The first and second groups in the optical communication optical system of Example 1 constitute a Galilean type optical system.

[0086] [Table 1] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 149.675 18.367 1.50122 1.50099 1.50088 3 SPH -94.791 5.000 1.79930 1.79885 1.79863 4 SPH 412.690 12.169 5 SPH 286.055 14.243 1.50122 1.50088 1.50088 6 SPH -124.439 10.000 7 SPH INF 14.993 8 SPH -118.238 5.000 1.50122 1.50065 1.50088 9 SPH 78.758 14.464 1.76444 1.76413 1.76398 10 SPH -531.641 144.766 11 ASP 312.917 5.000 1.50122 1.50065 1.50088 12 ASP 66.869 2.000 13 SPH INF 4.000 1.50122 1.50065 1.50088 14 SPH 21.310 200.000 15 SPH INF 5.000 1.44426 1.44402 1.44390 16 SPH INF 5.000 17 SPH INF 5.000 1.44426 1.44402 1.44390 18 SPH INF 5.000 19 SPH INF 5.000 1.44426 1.44402 1.44390 20 SPH INF 5.000 21 SPH INF 5.000 1.44426 1.44402 1.44390 22 SPH INF 50.000 23 SPH -28.107 3.000 1.50122 1.50065 1.50088 24 SPH 19.812 2.000 25 SPH 24.377 10.000 1.76444 1.76413 1.76398 26 SPH -19.730 2.000 1.50122 1.50065 1.50088 27 SPH 14.793 2.000 28 SPH 20.610 8.000 1.76444 1.76413 1.76398 29 ASP -105.469 53.987

[0087] [Table 2] Surface Number K A4 A6 A8 A10 11 0.000 -1.807E-05 -2.735E-07 -1.001E-09 -2.258E-11 12 0.000 -1.936E-05 -3.710E-07 -4.486E-09 -1.910E-13 29 0.000 -2.037E-06 -3.416E-08 -4.865E-11 -1.207E-12

[0088] [Table 3] Vertex angle (°) Rotation angle (°) Equation (2) 2 12.814 6.407 4 6.354 1.589 6 4.217 0.703 8 3.106 0.388 10 2.501 0.250 12 2.068 0.172 14 1.756 0.125 16 1.519 0.095

[0089] Example 2 FIG. 9 is a front view showing a schematic configuration of the optical communication system of the second embodiment, FIG. 10 is a spherical aberration diagram of the optical communication system of the second embodiment excluding the wedge prism at a wavelength of 1550 nm, and FIG. 11 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of the second embodiment. Table 4 shows the numerical data of the optical communication system, Table 5 shows the numerical data of the aspheric coefficients, and Table 6 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of the formula (2) at that time. In Table 4, surface numbers 1 to 13 represent the first group, surface numbers 14 to 21 represent the second group, surface numbers 22 to 29 represent the third group, and surface numbers 30 to 36 represent the fourth group. The first group and the second group in the optical communication system of the second embodiment constitute a Keplerian optical system.

[0090] [Table 4] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 161.898 14.000 1.60019 1.59993 1.59980 3 SPH -161.898 3.000 4 SPH -149.438 5.032 1.79930 1.79885 1.79863 5 SPH -247.836 37.000 6 SPH 90.591 11.000 1.50122 1.50099 1.50088 7 SPH -200.913 5.000 1.91169 1.91103 1.91070 8 SPH 120.161 129.031 9 SPH INF 8.035 10 SPH -216.546 5.000 1.50122 1.50099 1.50088 11 SPH -61.786 1.133 12 SPH 26.886 7.000 1.79930 1.79885 1.79863 13 SPH 18.887 54.770 14 SPH INF 53.986 15 ASP 105.469 8.000 1.76444 1.76413 1.76398 16 SPH -20.610 2.000 17 SPH -14.793 2.000 1.50122 1.50099 1.50088 18 SPH 19.730 10.000 1.76444 1.76413 1.76398 19 SPH -24.377 2.000 20 SPH -19.812 3.000 1.50122 1.50099 1.50088 21 SPH 28.107 50.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 5.000 24 SPH INF 5.000 1.44426 1.44402 1.44390 25 SPH INF 5.000 26 SPH INF 5.000 1.44426 1.44402 1.44390 27 SPH INF 5.000 28 SPH INF 5.000 1.44426 1.44402 1.44390 29 SPH INF 50.000 30 SPH -28.107 3.000 1.50122 1.50099 1.50088 31 SPH 19.812 2.000 32 SPH 24.377 10.000 1.76444 1.76413 1.76398 33 SPH -19.730 2.000 1.50122 1.50099 1.50088 34 SPH 14.793 2.000 35 SPH 20.610 8.000 1.76444 1.76413 1.76398 36 ASP -105.469 53.986

[0091] [Table 5] Surface number K A4 A6 A8 A10 15 0.000 2.037E-06 3.416E-08 4.865E-11 1.207E-12 36 0.000 -2.037E-06 -3.416E-08 -4.865E-11 -1.207E-12

[0092] [Table 6] Vertex angle (°) Rotation angle (°) Equation (2) 2 12.660 6.330 4 6.278 1.570 6 4.167 0.695 8 3.109 0.389 10 2.471 0.247 12 2.043 0.170 14 1.735 0.124 16 1.501 0.094

[0093] Example 3 FIG. 12 is a front view showing a schematic configuration of the optical communication system of Example 3, FIG. 13 is a spherical aberration diagram of the optical communication system of Example 3 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 14 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 3. Table 7 shows the numerical data of the optical communication system, Table 8 shows the numerical data of the aspheric coefficients, and Table 9 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 7, surface numbers 1 to 10 represent the first group, surface numbers 11 to 14 represent the second group, surface numbers 15 to 22 represent the third group, and surface numbers 23 to 29 represent the fourth group. The first and second groups in the optical communication system of Example 3 constitute a Galileo type optical system.

[0094] [Table 7] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 149.675 18.367 1.50122 1.50099 1.50088 3 SPH -94.791 5.000 1.79930 1.79885 1.79863 4 SPH 412.690 12.169 5 SPH 286.055 14.243 1.50122 1.50088 1.50088 6 SPH -124.439 10.000 7 SPH INF 14.993 8 SPH -118.238 5.000 1.50122 1.50065 1.50088 9 SPH 78.758 14.464 1.76444 1.76413 1.76398 10 SPH -531.641 144.766 11 ASP 312.917 5.000 1.50122 1.50065 1.50088 12 ASP 66.869 2.000 13 SPH INF 4.000 1.50122 1.50065 1.50088 14 SPH 21.310 200.000 15 SPH INF 5.000 1.673939 1.673623 1.673465 16 SPH INF 5.000 17 SPH INF 5.000 1.673939 1.673623 1.673465 18 SPH INF 5.000 19 SPH INF 5.000 1.673939 1.673623 1.673465 20 SPH INF 5.000 21 SPH INF 5.000 1.673939 1.673623 1.673465 22 SPH INF 50.000 23 SPH -28.107 3.000 1.50122 1.50065 1.50088 24 SPH 19.812 2.000 25 SPH 24.377 10.000 1.76444 1.76413 1.76398 26 SPH -19.730 2.000 1.50122 1.50065 1.50088 27 SPH 14.793 2.000 28 SPH 20.610 8.000 1.76444 1.76413 1.76398 29 ASP -105.469 53.987

[0095] [Table 8] Surface number K A4 A6 A8 A10 11 0.000 -1.807E-05 -2.735E-07 -1.001E-09 -2.258E-11 12 0.000 -1.936E-05 -3.710E-07 -4.486E-09 -1.910E-13 29 0.000 -2.037E-06 -3.416E-08 -4.865E-11 -1.207E-12

[0096] [Table 9] Vertex angle (°) Rotation angle (°) Equation (2) 2 8.405 4.203 4 4.181 1.045 6 2.774 0.462 8 2.068 0.259 10 1.642 0.164 12 1.355 0.113 13 1.244 0.096

[0097] Example 4 FIG. 15 is a front view showing a schematic configuration of the optical communication system of Example 4, FIG. 16 is a spherical aberration diagram of the optical communication system of Example 4 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 17 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 4. Table 10 shows the numerical data of the optical communication system, Table 11 shows the numerical data of the aspheric coefficients, and Table 12 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 10, surface numbers 1 to 13 represent the first group, surface numbers 14 to 21 represent the second group, surface numbers 22 to 29 represent the third group, and surface numbers 30 to 36 represent the fourth group. The first group and the second group in the optical communication system of Example 4 constitute a Keplerian optical system.

[0098] [Table 10] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 161.898 14.000 1.60019 1.59993 1.59980 3 SPH -161.898 3.000 4 SPH -149.438 5.032 1.79930 1.79885 1.79863 5 SPH -247.836 37.000 6 SPH 90.591 11.000 1.50122 1.50099 1.50088 7 SPH -200.913 5.000 1.91169 1.91103 1.91070 8 SPH 120.161 129.031 9 SPH INF 8.035 10 SPH -216.546 5.000 1.50122 1.50099 1.50088 11 SPH -61.786 1.133 12 SPH 26.886 7.000 1.79930 1.79885 1.79863 13 SPH 18.887 54.770 14 SPH INF 53.986 15 ASP 105.469 8.000 1.76444 1.76413 1.76398 16 SPH -20.610 2.000 17 SPH -14.793 2.000 1.50122 1.50099 1.50088 18 SPH 19.730 10.000 1.76444 1.76413 1.76398 19 SPH -24.377 2.000 20 SPH -19.812 3.000 1.50122 1.50099 1.50088 21 SPH 28.107 50.000 22 SPH INF 5.000 1.42855 1.42843 1.42837 23 SPH INF 5.000 24 SPH INF 5.000 1.42855 1.42843 1.42837 25 SPH INF 5.000 26 SPH INF 5.000 1.42855 1.42843 1.42837 27 SPH INF 5.000 28 SPH INF 5.000 1.42855 1.42843 1.42837 29 SPH INF 50.000 30 SPH -28.107 3.000 1.50122 1.50099 1.50088 31 SPH 19.812 2.000 32 SPH 24.377 10.000 1.76444 1.76413 1.76398 33 SPH -19.730 2.000 1.50122 1.50099 1.50088 34 SPH 14.793 2.000 35 SPH 20.610 8.000 1.76444 1.76413 1.76398 36 ASP -105.469 53.986

[0099] [Table 11] Surface number K A4 A6 A8 A10 15 0.000 2.037E-06 3.416E-08 4.865E-11 1.207E-12 36 0.000 -2.037E-06 -3.416E-08 -4.865E-11 -1.207E-12

[0100] [Table 12] Vertex angle (°) Rotation angle (°) Equation (2) 2 13.129 6.565 4 6.508 1.627 6 4.319 0.720 8 3.222 0.403 10 2.562 0.256 12 2.118 0.177 14 1.799 0.129 16 1.557 0.097 16.6 1.495 0.090

[0101] Example 5 FIG. 18 is a front view showing a schematic configuration of the optical communication system of the fifth embodiment, FIG. 19 is a spherical aberration diagram of the optical communication system of the fifth embodiment except for the wedge prism at a wavelength of 1550 nm, and FIG. 20 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of the fifth embodiment. Table 13 shows the numerical data of the optical communication system, Table 14 shows the numerical data of the aspheric coefficients, and Table 15 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of the formula (2) at that time. In Table 13, surface numbers 1 to 12 represent the first group, surface numbers 13 to 20 represent the second group, surface numbers 21 to 28 represent the third group, and surface numbers 29 to 35 represent the fourth group. The first group and the second group in the optical communication system of the fifth embodiment constitute a Keplerian optical system.

[0102] [Table 13] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 161.898 14.000 1.60019 1.59993 1.59980 3 SPH -161.898 3.000 4 SPH -149.438 5.032 1.79930 1.79885 1.79863 5 SPH -247.836 37.000 6 SPH 90.591 11.000 1.50122 1.50099 1.50088 7 SPH -200.913 5.000 1.91169 1.91103 1.91070 8 SPH 120.161 137.066 9 SPH -216.546 5.000 1.50122 1.50099 1.50088 10 SPH -61.786 1.133 11 SPH 26.886 7.000 1.79930 1.79885 1.79863 12 SPH 18.887 54.770 13 SPH INF 74.688 14 SPH -312.954 6.000 1.76444 1.76413 1.76398 15 ASP -28.120 2.000 16 SPH -22.445 2.000 1.50122 1.50099 1.50088 17 SPH 62.550 7.000 1.76444 1.76413 1.76398 18 SPH -27.409 1.000 19 SPH -27.023 3.000 1.50122 1.50099 1.50088 20 SPH 109.433 50.000 21 SPH INF 5.000 1.42855 1.42843 1.42837 22 SPH INF 5.000 23 SPH INF 5.000 1.42855 1.42843 1.42837 24 SPH INF 5.000 25 SPH INF 5.000 1.42855 1.42843 1.42837 26 SPH INF 5.000 27 SPH INF 5.000 1.42855 1.42843 1.42837 28 SPH INF 50.000 29 SPH -109.433 3.000 1.50122 1.50099 1.50088 30 SPH 27.023 1.000 31 SPH 27.409 7.000 1.76444 1.76413 1.76398 32 SPH -62.550 2.000 1.50122 1.50099 1.50088 33 SPH 22.445 2.000 34 SPH 28.120 6.000 1.76444 1.76413 1.76398 35 ASP 312.954 74.688

[0103] [Table 14] Surface number K A4 A6 A8 A10 14 0.000 -1.663E-06 1.158E-10 -8.842E-13 -2.575E-14 35 0.000 1.663E-06 -1.158E-10 8.842E-13 2.575E-14

[0104] [Table 15] Vertex angle (°) Rotation angle (°) Equation (2) 2 7.557 3.779 4 3.763 0.941 6 2.499 0.417 8 1.865 0.233 10 1.482 0.148 12 1.226 0.102 12.78 1.147 0.090

[0105] Example 6 FIG. 21 is a front view showing a schematic configuration of the optical communication system of Example 6, FIG. 22 is a spherical aberration diagram of the optical communication system of Example 6 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 23 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 6. Table 16 shows the numerical data of the optical communication system, Table 17 shows the numerical data of the aspheric coefficients, and Table 18 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 16, surface numbers 1 to 9 represent the first group, surface numbers 10 to 15 represent the second group, surface numbers 16 to 23 represent the third group, and surface numbers 24 to 31 represent the fourth group. The first and second groups in the optical communication system of Example 6 constitute a Galileo type optical system.

[0106] [Table 16] Face number Type RD n1530 n1550 n1565 1 SPH INF 0 2 SPH 96.726 24.809 1.501223 1.500992 1.500876 3 SPH -73.209 5.000 1.79930 1.79885 1.79863 4 SPH 157.840 10.000 5 SPH 158.340 19.288 1.501223 1.500992 1.500876 6 SPH -92.659 24.993 7 SPH -100.210 9.311 1.501223 1.500992 1.500876 8 SPH 63.019 16.334 1.76444 1.76413 1.76398 9 SPH -774.368 121.271 10 ASP 19.985 5.000 1.501223 1.500992 1.500876 11 ASP 13.894 6.860 12 ASP 27.312 5.000 1.76444 1.76413 1.76398 13 SPH 16.408 1.035 14 SPH 1276.950 4.000 1.76444 1.76413 1.76398 15 SPH 17.992 130.000 16 SPH INF 5.000 1.44426 1.44402 1.44390 17 SPH INF 5.000 18 SPH INF 5.000 1.44426 1.44402 1.44390 19 SPH INF 5.000 20 SPH INF 5.000 1.44426 1.44402 1.44390 21 SPH INF 5.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 80.000 24 SPH -151.718 3.000 1.501223 1.500992 1.500876 25 SPH 12.897 2.000 26 SPH 18.969 10.000 1.76444 1.76413 1.76398 27 SPH -12.679 0.700 28 SPH -10.966 5.000 1.501223 1.500992 1.500876 29 SPH 13.508 2.000 30 SPH 20.361 10.000 1.76444 1.76413 1.76398 31 ASP -139.791 33.697

[0107] [Table 17] Surface number K A4 A6 A8 A10 10 0.000 1.087E-04 1.004E-06 4.219E-08 -2.913E-10 11 0.000 2.001E-04 2.191E-06 1.223E-07 6.758E-09 12 0.000 -6.785E-04 -2.348E-05 -5.748E-07 4.073E-08 13 0.000 -1.211E-03 -4.482E-05 2.825E-06 -4.354E-08 14 0.000 -2.780E-05 -4.829E-07 -1.652E-09 2.205E-11

[0108] [Table 18] Vertex angle (°) Rotation angle (°) Equation (2) 2.81 18.195 6.475 4 12.653 3.163 6 8.368 1.395 8 6.236 0.780 10 4.954 0.495 12 4.094 0.341 14 3.476 0.248 16 3.007 0.188 18 2.639 0.147 20 2.340 0.117

[0109] Example 7 FIG. 24 is a front view showing a schematic configuration of the optical communication system of Example 7, FIG. 25 is a spherical aberration diagram of the optical communication system of Example 7 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 26 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 7. Table 19 shows the numerical data of the optical communication system, Table 20 shows the numerical data of the aspheric coefficients, and Table 21 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 19, surface numbers 1 to 13 represent the first group, surface numbers 14 to 21 represent the second group, surface numbers 22 to 29 represent the third group, and surface numbers 30 to 36 represent the fourth group. The first group and the second group in the optical communication system of Example 7 constitute a Keplerian optical system.

[0110] [Table 19] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 161.898 14.000 1.60019 1.59993 1.59980 3 SPH -161.898 3.000 4 SPH -149.438 5.032 1.79930 1.79885 1.79863 5 SPH -247.836 37.000 6 SPH 90.591 11.000 1.50122 1.50099 1.50088 7 SPH -200.913 5.000 1.91169 1.91103 1.91070 8 SPH 120.161 129.031 9 SPH 0.000 8.035 10 SPH -216.546 5.000 1.501223 1.500992 1.500876 11 SPH -61.786 1.133 12 SPH 26.886 7.000 1.799296 1.798853 1.798632 13 SPH 18.887 54.770 14 SPH INF 37.615 15 ASP 43.635 7.000 1.764439 1.764133 1.763981 16 SPH -16.150 1.066 17 SPH -12.014 3.000 1.501223 1.500992 1.500876 18 SPH 13.328 6.000 1.764439 1.764133 1.763981 19 SPH -17.670 1.000 20 SPH -14.335 3.000 1.501223 1.500992 1.500876 21 SPH 14.532 50.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 5.000 24 SPH INF 5.000 1.44426 1.44402 1.44390 25 SPH INF 5.000 26 SPH INF 5.000 1.44426 1.44402 1.44390 27 SPH INF 5.000 28 SPH INF 5.000 1.44426 1.44402 1.44390 29 SPH INF 50.000 30 SPH -14.532 3.000 1.501223 1.500992 1.500876 31 SPH 14.335 1.000 32 SPH 17.670 6.000 1.764439 1.764133 1.763981 33 SPH -13.328 3.000 1.501223 1.500992 1.500876 34 SPH 12.014 1.066 35 SPH 16.150 7.000 1.764439 1.764133 1.763981 36 ASP -43.635 37.615

[0111] [Table 20] Surface number K A4 A6 A8 A10 14 0.000 -3.026E-06 1.246E-07 5.631E-10 1.079E-11 35 0.000 3.026E-06 -1.246E-07 -5.631E-10 -1.079E-11

[0112] [Table 21] Vertex angle (°) Rotation angle (°) Equation (2) 2.43 18.195 7.488 6 12.653 2.109 8 8.368 1.046 10 6.236 0.624 12 4.954 0.413 14 4.094 0.292 16 3.476 0.217 18 3.007 0.167

[0113] Example 8 FIG. 27 is a front view showing a schematic configuration of the optical communication system of Example 8, FIG. 28 is a spherical aberration diagram of the optical communication system of Example 8 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 29 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 8. Table 22 shows the numerical data of the optical communication system, Table 23 shows the numerical data of the aspheric coefficient, and Table 24 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 22, surface numbers 1 to 10 represent the first group, surface numbers 11 to 15 represent the second group, surface numbers 16 to 23 represent the third group, and surface numbers 24 to 30 represent the fourth group. The first group and the second group in the optical communication system of Example 8 constitute a Galileo type optical system.

[0114] [Table 22] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 147.178 18.476 1.501223 1.500992 1.500876 3 SPH -94.558 5.000 1.79930 1.79885 1.79863 4 SPH 418.410 10.000 5 SPH 287.165 14.117 1.501223 1.500992 1.500876 6 SPH -124.493 10.000 7 SPH INF 14.993 8 SPH -118.452 5.000 1.501223 1.500992 1.500876 9 SPH 78.912 14.283 1.76444 1.76413 1.76398 10 SPH -528.765 147.131 11 ASP 526.806 5.000 1.501223 1.500992 1.500876 12 ASP 64.080 2.000 13 SPH 39278.407 4.000 1.501223 1.500992 1.500876 14 SPH 17.844 100.000 15 SPH INF 5.000 16 SPH INF 5.000 1.44426 1.44402 1.44390 17 SPH INF 5.000 18 SPH INF 5.000 1.44426 1.44402 1.44390 19 SPH INF 5.000 20 SPH INF 5.000 1.44426 1.44402 1.44390 21 SPH INF 5.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 50.000 24 SPH -47.447 3.000 1.501223 1.500992 1.500876 25 SPH 13.378 2.000 26 SPH 16.633 10.000 1.76444 1.76413 1.76398 27 SPH -17.660 5.000 1.501223 1.500992 1.500876 28 SPH 10.286 2.000 29 SPH 15.534 10.000 1.76444 1.76413 1.76398 30 ASP -237.702 37.449

[0115] [Table 23] Surface Number K A4 A6 A8 A10 11 0.000 -1.772E-05 -2.785E-07 -1.460E-09 -5.802E-11 12 0.000 -1.968E-05 -4.042E-07 -6.430E-09 -5.495E-11 30 0.000 -2.117E-05 -2.197E-07 -1.837E-09 1.908E-11

[0116] [Table 24] Vertex angle (°) Rotation angle (°) Equation (2) 2.17 13.988 6.446 4 7.522 1.881 6 4.990 0.832 8 3.723 0.465 10 2.959 0.296 12 2.446 0.204 14 2.077 0.148 16 1.798 0.112

[0117] Example 9 FIG. 30 is a front view showing a schematic configuration of the optical communication system of Example 9, FIG. 31 is a spherical aberration diagram of the optical communication system of Example 9 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 32 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 9. Table 25 shows the numerical data of the optical communication system, Table 26 shows the numerical data of the aspheric coefficient, and Table 27 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 25, surface numbers 1 to 10 represent the first group, surface numbers 11 to 15 represent the second group, surface numbers 16 to 23 represent the third group, and surface numbers 24 to 30 represent the fourth group. The first and second groups in the optical communication system of Example 9 constitute a Galileo type optical system.

[0118] [Table 25] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 131.982 29.000 1.501223 1.500992 1.500876 3 SPH -61.619 5.000 1.79930 1.79885 1.79863 4 SPH -1296.849 11.404 5 SPH -349.081 15.605 1.50226 1.502368 1.502582 6 SPH -76.094 62.788 7 SPH INF 15.187 8 SPH -57.588 5.000 1.501223 1.500992 1.500876 9 SPH 61.231 13.351 1.76444 1.76413 1.76398 10 SPH -178.373 81.187 11 ASP INF 4.219 1.499711 1.499831 1.50007 12 ASP 25.840 3.760 13 SPH INF 3.500 1.501223 1.500992 1.500876 14 SPH 51.680 200.000 15 SPH INF 5.000 16 SPH INF 5.000 1.44426 1.44402 1.44390 17 SPH INF 5.000 18 SPH INF 5.000 1.44426 1.44402 1.44390 19 SPH INF 5.000 20 SPH INF 5.000 1.44426 1.44402 1.44390 21 SPH INF 5.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 50.000 24 SPH -28.107 3.000 1.501223 1.500992 1.500876 25 SPH 19.812 2.000 26 SPH 24.377 10.000 1.76444 1.76413 1.76398 27 SPH -19.730 2.000 1.501223 1.500992 1.500876 28 SPH 14.793 2.000 29 SPH 20.610 8.000 1.76444 1.76413 1.76398 30 ASP -105.469 53.986

[0119] [Table 26] Surface number K A4 A6 A8 A10 30 0.000 -2.037E-06 -3.416E-08 -4.865E-11 -1.207E-12

[0120] [Table 27] Vertex angle (°) Rotation angle (°) Equation (2) 2 12.630 6.315 4 6.262 1.566 6 4.155 0.693 8 3.100 0.388 10 2.464 0.246 12 2.083 0.174 14 1.730 0.124 16 1.497 0.094

[0121] Example 10 FIG. 33 is a front view showing a schematic configuration of the optical communication system of Example 10, FIG. 34 is a spherical aberration diagram of the optical communication system of Example 10 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 35 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 10. Table 28 shows the numerical data of the optical communication system, Table 29 shows the numerical data of the aspheric coefficients, and Table 30 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 28, surface numbers 1 to 13 represent the first group, surface numbers 14 to 21 represent the second group, surface numbers 22 to 29 represent the third group, and surface numbers 30 to 36 represent the fourth group. The first group and the second group in the optical communication system of Example 10 constitute a Keplerian optical system.

[0122] [Table 28] Face number Type RD n1530 n1550 n1565 1 STO INF 0 2 SPH 161.898 14.000 1.60019 1.59993 1.59980 3 SPH -161.898 3.000 4 SPH -149.438 5.032 1.79930 1.79885 1.79863 5 SPH -247.836 37.000 6 SPH 90.591 11.000 1.50122 1.50099 1.50088 7 SPH -200.913 5.000 1.91169 1.91103 1.91070 8 SPH 120.161 129.031 9 SPH INF 8.035 10 SPH -216.546 5.000 1.50122 1.50099 1.50088 11 SPH -61.786 1.133 12 SPH 26.886 7.000 1.799296 1.798853 1.798632 13 SPH 18.887 54.770 14 SPH INF 62.269 15 ASP 119.990 6.000 1.76444 1.76413 1.76398 16 SPH -25.540 2.000 17 SPH -19.168 2.000 1.50122 1.50099 1.50088 18 SPH 34.660 7.000 1.76444 1.76413 1.76398 19 SPH -25.540 1.000 20 SPH -23.952 3.000 1.50122 1.50099 1.50088 21 SPH 36.979 50.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 5.000 24 SPH INF 5.000 1.44426 1.44402 1.44390 25 SPH INF 5.000 26 SPH INF 5.000 1.44426 1.44402 1.44390 27 SPH INF 5.000 28 SPH INF 5.000 1.44426 1.44402 1.44390 29 SPH INF 50.000 30 SPH -36.979 3.000 1.50122 1.50099 1.50088 31 SPH 23.952 1.000 32 SPH 25.540 7.000 1.76444 1.76413 1.76398 33 SPH -34.660 2.000 1.50122 1.50099 1.50088 34 SPH 19.168 2.000 35 SPH 25.540 6.000 1.76444 1.76413 1.76398 36 ASP -119.990 62.269

[0123] [Table 29] Surface number K A4 A6 A8 A10 15 0.000 -1.203E-06 7.056E-09 4.578E-12 7.763E-14 36 0.000 1.203E-06 -7.056E-09 -4.578E-12 -7.763E-14

[0124] [Table 30] Vertex angle (°) Rotation angle (°) Equation (2) 2 10.099 5.050 4 5.019 1.255 6 3.333 0.556 8 2.487 0.311 10 1.977 0.198 12 1.634 0.136 14 1.388 0.099

[0125] Example 11 FIG. 36 is a front view showing a schematic configuration of the optical communication system of Example 11, FIG. 37 is a spherical aberration diagram of the optical communication system of Example 11 except for the wedge prism at a wavelength of 1550 nm, and FIG. 38 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 11. Table 31 shows the numerical data of the optical communication system, Table 32 shows the numerical data of the aspheric coefficients, and Table 33 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 31, surface numbers 1 to 10 represent the first group, surface numbers 11 to 15 represent the second group, surface numbers 16 to 23 represent the third group, and surface numbers 24 to 30 represent the fourth group. The first group and the second group in the optical communication system of Example 11 constitute a Galileo type optical system.

[0126] [Table 31] RD n1530 n1550 n1565 1 SPH INF 0 2 SPH 161.254 22.474 1.501223 1.500992 1.500876 3 SPH -98.686 5.000 1.79930 1.79885 1.79863 4 SPH 590.632 38.130 5 SPH 345.321 13.981 1.501223 1.500992 1.500876 6 SPH -127,326 11,959 7 SPH INF 14.281 8 SPH -119.969 5.001 1.501223 1.500992 1.500876 9 SPH 79,969 14,324 1.76444 1.76413 1.76398 10 SPH -574.073 127.323 11 ASP 142,686 5,000 1.501223 1.500992 1.500876 12 ASP 34,521 1,744 13 ASP INF 4,000 1.501223 1.500992 1.500876 14 ASP 56,203 150,000 15 SPH INF 5,000 16 SPH INF 5,000 1.44426 1.44402 1.44390 17 SPH INF 5,000 18 SPH INF 5,000 1.44426 1.44402 1.44390 19 SPH INF 5,000 20 SPH INF 5,000 1.44426 1.44402 1.44390 21 SPH INF 5,000 22 SPH INF 5,000 1.44426 1.44402 1.44390 23 SPH INF 50.000 24 SPH -60.861 3.000 1.501223 1.500992 1.500876 25 SPH 24.956 1.138 26 SPH 26.402 7.000 1.76444 1.76413 1.76398 27 SPH -53.543 2.000 1.501223 1.500992 1.500876 28 SPH 21.347 2.000 29 SPH 28.335 6.000 1.76444 1.76413 1.76398 30 ASP -267.951 71.253

[0127] [Table 32] Surface number K A4 A6 A8 A10 11 0.000 -1.840E-05 -1.722E-07 -3.579E-10 -4.350E-13 12 0.000 -1.529E-05 -3.232E-07 -2.590E-09 1.380E-11 13 0.000 3.162E-07 -5.549E-09 -1.721E-10 2.517E-13 14 0.000 -3.698E-06 8.973E-08 1.537E-09 -9.308E-12 30 0.000 5.954E-07 -3.323E-09 -4.219E-12 8.334E-15

[0128] [Table 33] Vertex angle (°) Rotation angle (°) Equation (2) 2 8.402 4.201 4 4.181 1.045 6 2.777 0.463 8 2.072 0.259 10 1.647 0.165 12 1.362 0.114 13.44 1.210 0.090

[0129] Example 12 FIG. 39 is a front view showing a schematic configuration of the optical communication system of Example 12, FIG. 40 is a spherical aberration diagram of the optical communication system of Example 12 excluding the wedge prism at a wavelength of 1550 nm, and FIG. 41 is a diagram showing the wavelength dependency of the focus shift amount at wavelengths of 1530 nm to 1565 nm of the optical communication system of Example 12. Table 34 shows the numerical data of the optical communication system, and Table 35 shows the rotation angle for each apex angle for vibration correction of the vibration angle of 100 mrad of the wedge prism, and the numerical data of formula (2) at that time. In Table 34, surface numbers 1 to 10 represent the first group, surface numbers 11 to 15 represent the second group, surface numbers 16 to 23 represent the third group, and surface numbers 24 to 31 represent the fourth group. The first group and the second group in the optical communication system of Example 12 constitute a Galileo type optical system.

[0130] [Table 34] Face number Type RD n1530 n1550 n1565 1 SPH INF 0 2 SPH 183.986 21.000 1.60019 1.59993 1.59980 3 SPH -82.488 5.032 1.79930 1.79885 1.79863 4 SPH 850.996 10.000 5 SPH 208.976 10.959 1.50258 1.50237 1.50226 6 SPH -762.299 5.000 7 SPH INF 5.000 8 SPH -219.133 10.000 1.50122 1.50099 1.50088 9 SPH -117.612 1.000 10 SPH -325.572 7.000 1.76336 1.76301 1.76284 11 SPH -508.598 170.126 12 SPH 100.000 5.000 1.50258 1.50237 1.50226 13 SPH 62.026 2.899 14 SPH INF 3.500 1.50122 1.50099 1.50088 15 SPH 25.840 125.000 16 SPH INF 5.000 1.44426 1.44402 1.44390 17 SPH INF 5.000 18 SPH INF 5.000 1.44426 1.44402 1.44390 19 SPH INF 5.000 20 SPH INF 5.000 1.44426 1.44402 1.44390 21 SPH INF 5.000 22 SPH INF 5.000 1.44426 1.44402 1.44390 23 SPH INF 125.000 24 SPH 37.302 5.000 1.50122 1.50099 1.50088 25 SPH -24.491 0.999 26 SPH -28.633 3.000 1.76113 1.76070 1.76049 27 SPH 12.710 6.000 1.50122 1.50099 1.50088 28 SPH 241.751 2.000 29 SPH 116.415 2.000 1.50122 1.50099 1.50088 30 SPH 17.456 6.000 1.87300 1.87315 1.87296 31 SPH -150.303 50.709

[0131] [Table 35] Vertex Angle (°) Rotation Angle (°) Equation (2) 2 10.962 5.481 4 5.445 1.361 6 3.615 0.603 8 2.698 0.337 10 2.145 0.215 12 1.773 0.148 14 1.506 0.108 15.2 1.378 0.091

[0132] Tables 36 and 37 show the values ​​calculated from the above formulas (1), (3) and (4) in Examples 1 to 12.

[0133] [Table 36] Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Ff / Bf 6.567 6.494 6.567 6.494 3.896 12.994 |C1-C2| 6.830 1.346 6.841 1.342 0.000 14.715 n 1.44402 1.44402 1.673623 1.42843 1.44402 1.44402

[0134] [Table 37] Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Ff / Bf 9.740 7.778 6.476 5.194 4.335 5.632 |C1-C2| 0.369 4.062 9.521 0.097 8.469 13.879 n 1.44402 1.44402 1.44402 1.44402 1.44402 1.44402 [Explanation of symbols]

[0135] 1 Optical communication equipment 10 Casing 11 Group 1 12 Second group 13 Group 3 14 Group 4 20 Optical Fiber 21 Single mode fiber 22 Connectors 31 Beam splitter 32 Segmented photodiode 33 Control Unit 41, 42, 43, 44 Wedge Prism 131, 132 Wedge Prism Pair OA optical axis

Claims

1. An optical communication optical system disposed on an optical path of a signal light emitted from a light-emitting element and transmitted, or a signal light incident on a light-receiving element and received, a first group, a second group, a third group, and a fourth group arranged in this order from the opposite side to the light emitting element or the light receiving element, the first group changes a beam diameter of the signal light so as to be smaller at an end of the first group on the second group side in an optical axis direction; the second group changes a beam diameter of the signal light so as to be smaller at an end of the second group on the third group side in the optical axis direction; the third group is composed of two pairs of wedge prisms, each pair of wedge prisms being composed of two wedge prisms that rotate in opposite directions to each other and at the same rotation angle; the fourth group changes a beam diameter of the signal so as to be smaller at an end of the fourth group on the side of the light emitting element or the light receiving element in the optical axis direction; An optical communication system that satisfies the following formulas (1) and (2): 3.89<Ff / Bf<14.00...(1) 0.090<R / a<6.565...(2) (In formula (1), Ff represents the focal length (mm) of the first group, Bf represents the focal length (mm) of the second group, and in formula (2), R represents the rotation angle of the wedge prism in one or the other of the wedge prism pairs, and a represents the apex angle of the wedge prism in one or the other of the wedge prism pairs).

2. The optical communication system according to claim 1 , which satisfies formula (3). |C1-C2|≦14.715...(3) (In equation (3), C1 represents the amount of movement (μm) of the focal position of the signal light having a wavelength of 1530 nm when the focal position of the signal light having a wavelength of 1550 nm is used as the reference, and C2 represents the amount of movement (μm) of the focal position of the signal light having a wavelength of 1565 nm when the focal position of the signal light having a wavelength of 1550 nm is used as the reference).

3. The optical communication system according to claim 1 , which satisfies formula (4). 1.4<n<1.674...Formula (4) (In formula (4), n represents the refractive index of light with a wavelength of 1550 nm in the material of the wedge prism).

4. The optical communication system according to claim 1 , wherein the second group and the fourth group change a beam diameter of the signal light between both groups so that the signal light becomes collimated light.

5. The optical communication system according to claim 1 , wherein at least one of the first group, the second group, and the fourth group includes an aspheric lens.

6. An optical communication device comprising the optical communication system according to any one of claims 1 to 5.

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