Optical planetarium and planetarium system having the same

Abstract

To provide an optical planetarium capable of appropriately reproducing various starry skies while compactly forming devices.SOLUTION: An optical planetarium 10 includes: a projector 12 for projecting a star image; a diurnal shaft support mechanism 21 constituted so as to rotate the projector 12 around a diurnal axis 81; a latitude shaft support mechanism 23 constituted so as to rotate the projector 12 around a latitude axis 82 orthogonal to the diurnal axis 81; an orientation shaft support mechanism 25 constituted so as to rotate the projector 12 around an orientation axis 83 vertically provided; and a latitude axis inclination angle change mechanism 40 constituted so as to change an angle formed between the latitude axis 82 and a horizontal plane within a predetermined range.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an optical planetarium and a planetarium system having the same. [Background technology]

[0002] 1. Modern 3-axis The configuration of a typical optical planetarium, which is currently the most popular, is shown in FIG. 6. In the optical planetarium 110, a hemispherical northern sky projector 111a and a southern sky projector 111b are provided facing each other as projectors 112 for projecting fixed stars. These are called the star sphere 111. The star sphere 111 is rotatable around a diurnal axis 181. This star sphere 111 is supported on a mounting fork 122 so as to be rotatable around a horizontally-set latitudinal axis 182 that is perpendicular to the diurnal axis 181. By rotating the star sphere 111 around the latitudinal axis 182, the inclination angle between the diurnal axis 181 and the horizontal plane can be freely changed.

[0003] The stars projected from the star sphere 111 are arranged in coordinates based on equatorial coordinates with the Earth's rotation axis as the reference, so that the diurnal axis 181 points to the current celestial north pole and celestial south pole. Therefore, by rotating the star sphere 111 around the diurnal axis 181, the diurnal motion of the stars is reproduced on the dome screen. Also, by rotating the star sphere 111 around the latitudinal axis 182, the optical planetarium 110 can reproduce the starry sky of an observation site at any latitude on Earth.

[0004] In recent planetariums, the mainstream is now the arrangement of spectator seats facing in one direction, rather than the traditional arrangement of seats in a concentric circle facing the center of the dome. This arrangement makes it easier for the commentator and the audience to align their gazes in the same direction, making it easier for the commentator to correctly explain celestial objects to all audience members. On the other hand, since a specific direction is set as the front, it is difficult to see the opposite side of the front. For example, if the south side is set as the front, both the commentator and the audience must look back to explain celestial objects on the north side. This is inconvenient, so the optical planetarium 110 is provided with an azimuth axis 183 that rotates the entire planetarium horizontally. In this way, the system that allows the front direction to be freely changed is becoming widespread. As described above, in recent years, optical planetariums 110 that have three axes, a diurnal axis 181, a latitudinal axis 182, and an azimuth axis 183, are common in order to reproduce the movements of celestial objects such as fixed stars. This type of optical planetarium 110 system is called the modern three-axis system.

[0005] 2. Classical 4-axis type In the past, optical planetariums 210 equipped with a diurnal axis 281, a latitudinal axis 282, and a precession axis 285, as shown in FIG. 7, were common in order to reproduce the long-term change in the axis of rotation, known as precession. This type of optical planetarium 210 is called the classical three-axis type. The northern star sphere 211a and the southern star sphere 211b are configured to project a starry sky based on ecliptic coordinates based on the plane of the Earth's orbit, rather than on the Earth's axis of rotation, and are configured to be rotatable around the precession axis 285. This precession axis 285 is held by a precession axis holder 291, and the entire precession axis holder 291 is rotatable around the diurnal axis 281. This precession axis holder 291 holds the angle between the diurnal axis 281 and the precession axis 285 at approximately 23.4°. This angle is the tilt angle of the Earth's equator with respect to the ecliptic plane. The diurnal axis 281 is held by the latitudinal axis 282, and the starry sky at an observation site at any latitude can be reproduced by rotating the latitudinal axis 282, just like in the case of a modern three-axis type. The classical three-axis type optical planetarium 210 can reproduce not only the current movement of the stars in which the current North Star (α Ursae Minoris: Polaris) is the North Star, but also the movement of the stars in the future, for example, 11,000 years from now, when Vega in Lyra will be the North Star, by rotating the precession axis 285.

[0006] Furthermore, an optical planetarium 210 is also known that is equipped with an azimuth axis 283 that rotates the entirety horizontally in addition to the classical three-axis type. This type of optical planetarium 210 is referred to as a classical four-axis type.

[0007] In the classical three-axis and classical four-axis optical planetariums 210, the star ball 211a for the northern sky and the star ball 211b for the southern sky are tilted and installed on the precession axis holder 291, which results in a large size of the device. A large optical planetarium 210 may obstruct the view of the audience. For this reason, the classical three-axis and classical four-axis optical planetariums 210 are not often used in recent years, and the use of the modern three-axis optical planetarium 110 has become mainstream. With the modern three-axis type, the star ball 111 can be compactly arranged, and the optical planetarium 110 does not obstruct the view of the audience.

[0008] A conventional optical planetarium like that described above is disclosed in Patent Document 1, for example.

[0009] 3. Multi-axis synthetic control In a modern three-axis optical planetarium 110, precession and the like cannot be reproduced by rotation around one axis. For this reason, the angles around the three axes are controlled by a computer, and precession and the like are virtually reproduced by a three-axis composite motion. The star sphere 111 can theoretically take any attitude angle by combining rotations around the three axes of the diurnal axis 181, the latitudinal axis 182, and the azimuth axis 183. For this reason, by precisely controlling the angles around these three axes, not only precession but also rotation around any point on the celestial sphere can be reproduced, so that, for example, the starry sky seen from a planet other than the Earth can be reproduced. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Publication No. 4-204586 Summary of the Invention [Problem to be solved by the invention]

[0011] In multi-axis synthesis control using the modern three-axis system, if the two axes come close to each other, such as when the diurnal axis 181 overlaps with the azimuth axis 183, the degree of freedom of movement is reduced and the starry sky may not be reproduced properly. With the four-axis synthesis movement using the classical four-axis system, such a reduction in the degree of freedom of movement is prevented, and the starry sky can be reproduced with high accuracy. However, with the classical four-axis system, the optical planetarium 210 becomes more complex and larger than with the modern three-axis system.

[0012] An object of the present invention is to provide an optical planetarium that can appropriately reproduce a variety of starry skies while making the device compact. [Means for solving the problem]

[0013] According to one aspect of the present invention, an optical planetarium includes a projector that projects images of stars, a diurnal axis support mechanism configured to enable the projector to rotate around a diurnal axis, a latitudinal axis support mechanism configured to enable the projector to rotate around a latitudinal axis perpendicular to the diurnal axis, an azimuth axis support mechanism configured to enable the projector to rotate around a vertically arranged azimuth axis, and a latitudinal axis inclination angle change mechanism configured to change the angle between the latitudinal axis and a horizontal plane within a predetermined range. Effect of the Invention

[0014] According to the present invention, in an optical planetarium, it is possible to appropriately reproduce a variety of starry skies while making the device compact. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a perspective view showing an outline of a configuration example of an optical planetarium according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating an outline of a configuration example of a planetarium system according to an embodiment. [Diagram 3] FIG. 3 is a diagram for explaining the case of reproducing the diurnal motion of the stars in the future sky 11,000 years from the present. [Figure 4]FIG. 4 is a flowchart illustrating an example of control of the optical planetarium according to an embodiment. [Figure 5A] FIG. 5A shows an example of the change in angle around the diurnal axis, latitudinal axis, and azimuthal axis when reproducing the diurnal motion of the starry sky 11,000 years from now using a modern three-axis optical planetarium. [Figure 5B] FIG. 5B is a diagram showing an example of the change in angle around the diurnal axis, latitudinal axis, azimuthal axis, and oscillation axis when reproducing the diurnal motion of the starry sky 11,000 years from now using a new four-axis optical planetarium according to one embodiment. [Figure 6] FIG. 6 is a perspective view showing an outline of a configuration example of a modern three-axis optical planetarium. [Figure 7] FIG. 7 is a perspective view showing an outline of a configuration example of a classical four-axis type optical planetarium. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [Configuration of an optical planetarium] An embodiment will be described with reference to the drawings. The optical planetarium according to this embodiment is a four-axis projector that is a modern three-axis optical planetarium with a swing axis for tilting the latitude axis within a certain range. By having four axes, it is possible to appropriately reproduce precession and rotational motion around any point on the celestial sphere, such as the starry sky seen from a planet other than the earth. In addition, the configuration according to this embodiment allows the device to be made compact. The system of the optical planetarium according to this embodiment is referred to as a new four-axis system.

[0017] FIG. 1 shows an outline of an example of the configuration of an optical planetarium 10 according to this embodiment. As shown in FIG. 1, the optical planetarium 10 according to this embodiment includes a projector 12 for projecting star images, similar to a conventional modern three-axis optical planetarium 110. In the example shown in FIG. 1, the projector 12 includes a star ball 11 including a northern sky projector 11a and a southern sky projector 11b, each of which is hemispherical and mounted facing each other. The star ball 11 is supported by a diurnal axis support mechanism 21 so as to be rotatable about a diurnal axis 81. The diurnal axis support mechanism 21 includes, for example, an axis member aligned with the diurnal axis 81, a bearing for receiving the axis member, a motor and a reducer for rotating the axis member, and an encoder for detecting the rotation angle. The configuration of the diurnal axis support mechanism 21 is not limited to this, and may be any. For example, the diurnal axis support mechanism 21 may be formed using a circular rail and a slider provided on the periphery of a disk that slides against the rail.

[0018] The star ball 11 is supported on the mount fork 22 by a latitudinal axis support mechanism 23 so that it can rotate around a latitudinal axis 82 that is perpendicular to the diurnal axis 81. The latitudinal axis support mechanism 23 can also have a variety of configurations, for example, it includes a shaft member, a bearing, a motor, a reducer, an encoder, etc. The optical planetarium 10 is configured so that the inclination angle between the diurnal axis 81 and the horizontal plane can be freely changed by rotating the star ball 11 around the latitudinal axis 82.

[0019] As with conventional modern three-axis optical planetariums 110, the stars projected from the star sphere 11 are arranged in equatorial coordinates based on the Earth's rotation axis. As the star sphere 11 rotates around the diurnal axis 81, the diurnal motion of the stars is reproduced on the dome screen. As the star sphere 11 rotates around the horizontal latitudinal axis 82, the starry sky of an observation site at any latitude on Earth is reproduced.

[0020] The optical planetarium 10 is also configured to rotate around a vertically installed azimuth axis 83 so as to rotate the entirety in a horizontal direction. That is, the mount fork 22 is supported by an azimuth axis support mechanism 25 so as to be rotatable around the azimuth axis 83 with respect to a base 27 fixed to the ground. The azimuth axis support mechanism 25 may also have various configurations, for example, a shaft member, a bearing, a motor, a reducer, an encoder, etc. The mount fork 22 rotates around the azimuth axis 83, so that the direction of the front can be freely changed. The diurnal axis 81, the latitude axis 82, and the azimuth axis 83 are arranged to intersect at the center of the star sphere 11.

[0021] The optical planetarium 10 according to this embodiment further includes a latitudinal axis tilt angle changing mechanism 40 configured to change the angle between the latitudinal axis 82 and the horizontal plane within a predetermined range. In particular, the optical planetarium 10 according to this embodiment is provided with a swing axis 84 around which the latitudinal axis 82 rotates. The swing axis 84 is provided at the center of the star sphere 11 so as to be perpendicular to the azimuth axis 83 and the latitudinal axis 82.

[0022] The frame fork 22 of this embodiment has an arc shape centered on the center of the star sphere 11 so that the latitude axis 82 can rotate around the swing axis 84. The support part 26, which rotates around the azimuth axis 83 provided on the azimuth axis support mechanism 25, is provided with an arc rail 41 centered on the center of the star sphere 11. The frame fork 22 has a slider 43 that slides on this rail 41. The frame fork 22 is supported by the support part 26 on the azimuth axis support mechanism 25 via the rail 41 and the slider 43. It is preferable that the rail 41 and the slider 43 are provided with cross roller bearings. The frame fork 22 is provided with an arc rack gear 45 along the arc rail 41 and the slider 43, and the support part 26 is provided with a pinion gear 47 that drives the rack gear 45. The pinion gear 47 is driven by a swing axis motor 49. The tilt angle of the platform fork 22 is freely controlled by the operation of the oscillation shaft motor 49. The configuration of the latitudinal axis tilt angle changing mechanism 40 described here is one example, and other structures may be used for the latitudinal axis tilt angle changing mechanism 40 as long as they have a similar function. The movable range of the platform fork 22 around the oscillation shaft 84 is, for example, ±30°, but is not limited to this. In this case, the star sphere 11 can rotate around the oscillation shaft 84 passing through the center of the star sphere 11 within a range of ±30°.

[0023] As shown in FIG. 2, in the planetarium system 1 of this embodiment, the optical planetarium 10 as described above is placed in the center of a hemispherical dome 3 whose inner surface is a screen 2. The optical planetarium 10 projects images of stars onto the screen 2 on the inner surface of the dome 3. The operation of the optical planetarium 10 for this projection is controlled by a control device 4. This control also includes the rotation of the star ball 11 around a diurnal axis 81, a latitudinal axis 82, an azimuth axis 83, and a swing axis 84. The control device 4 includes a computer. The control device 4 includes an integrated circuit such as a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), or a Field Programmable Gate Array (FPGA). The control device 4 also includes a Read Only Memory (ROM), a Random Access Memory (RAM), a storage, an input device, a display device, various interfaces, and the like. The control device 4 operates according to a program or hardware.

[0024] [Optical planetarium operation] The operation of the new four-axis optical planetarium 10 according to this embodiment will be described below in comparison with the operation of the conventional modern three-axis optical planetarium 110 described with reference to FIG.

[0025] In both the star ball 11 of the new four-axis optical planetarium 10 according to this embodiment and the star ball 111 of the conventional modern three-axis optical planetarium 110, the stars are arranged in coordinates based on equatorial coordinates with the current rotation axis of the Earth as the reference. That is, for example, the star at the current celestial north pole is arranged on the diurnal axis 81 of the northern sky projector 11a. Specifically, although there is a deviation of just under 1°, the North Star (α Ursae Minoris: Polaris) is arranged near the celestial north pole, that is, near the diurnal axis 81 of the northern sky projector 11a.

[0026] As an example, let us assume that we want to reproduce the diurnal motion of the stars in the future, 11,000 years from now. In this case, in the northern sky, Vega in the constellation Lyra is located near the north celestial pole, although it does not completely coincide with the north celestial pole. When viewed from a point around 37° north latitude, as shown in Figure 3, Vega 911 appears at an altitude of approximately 37° in the northern sky and hardly moves at all. Polaris 912 rises in the northeastern sky and passes about 1° north of the zenith near zenith 913, because Polaris 912 and Vega 911 are approximately 52° apart. Other stars also undergo diurnal motion with Vega 911 as the center.

[0027] In reality, Polaris does not coincide perfectly with the North Celestial Pole even in the present day, and Vega will not coincide perfectly with the North Celestial Pole 11,000 years in the future, but for the sake of explanation, we will assume that Polaris coincides with the North Celestial Pole in the present day, and that Vega will coincide with the North Celestial Pole 11,000 years in the future, with Polaris passing near the zenith.

[0028] Consider a case where the movement of the starry sky at 37° north latitude 11,000 years in the future is reproduced by a three-axis composite movement using a conventional modern three-axis optical planetarium 110. In this case, the direction of the diurnal axis 181 of the optical planetarium 110 points in the direction of Polaris 912, and the angle around the azimuth axis 183 changes following the direction of Polaris 912. When Polaris 912 is sufficiently far from the zenith 913, the angular velocity around the azimuth axis 183 is small and no problem occurs.

[0029] However, even though the speed of the diurnal motion is not so fast, when Polaris 912 passes near the zenith 913, as shown by the arrow in FIG. 3, the azimuth angle of Polaris 912 changes suddenly, so that the rotation around the azimuth axis 183 must also become fast. When Polaris 912 completely passes the zenith 913, its speed momentarily becomes infinite. This is called a singular point. When Polaris 912 approaches the zenith 913, it means that the angle between the diurnal axis 181 and the azimuth axis 183 becomes small. When the altitude of Polaris 912 above the horizon is a°, the angle between the diurnal axis 181 and the azimuth axis 183 is (90-a)°. In other words, the phenomenon that occurs at the singular point occurs when the azimuth axis 183 and the diurnal axis 181 overlap, reducing the degree of freedom of motion. This phenomenon is equivalent to the so-called gimbal lock state. In the actual operation of the optical planetarium 110, there are limitations to the maximum speed and acceleration of rotation around the axis of rotation, so the optical planetarium 110 cannot accurately follow the ideal movement, resulting in unnatural movement.

[0030] The classical four-axis optical planetarium 210 described with reference to Fig. 7 can solve this problem by using four-axis composite motion. However, the classical four-axis optical planetarium 210 is large in size, and the optical planetarium 210 may obstruct the view of the audience.

[0031] In contrast, the new four-axis optical planetarium 10 according to this embodiment controls the rotation about four axes, i.e., the diurnal axis 81, the latitudinal axis 82, the azimuth axis 83, and the oscillation axis 84, thereby preventing the diurnal axis 81 and the azimuth axis 83 from coming too close to each other, thereby avoiding the above-mentioned problems that arise in the conventional modern three-axis system.

[0032] The new four-axis optical planetarium 10 according to this embodiment has two control modes: a fixed oscillation axis mode and a fixed azimuth axis mode. In the fixed oscillation axis mode, the angle around the oscillation axis 84 is fixed to a predetermined value, and the angles around each of the diurnal axis 81, the latitudinal axis 82, and the azimuth axis 83 are calculated, and the attitude of the star ball 11 is controlled. When the angle around the oscillation axis 84 is 0° and the latitudinal axis 82 is horizontal, this is equivalent to the case of a conventional modern three-axis type. In the fixed azimuth axis mode, the azimuth axis 83 is fixed to a predetermined value, and the angles around each of the diurnal axis 81, the latitudinal axis 82, and the oscillation axis 84 are calculated, and the attitude of the star ball 11 is controlled. It is known that in each mode, the angles around each axis can be mathematically calculated using matrix calculations or the like. Here, a description of this calculation is omitted.

[0033] Normally, the control is performed in the oscillation axis fixed mode in which the angle around the oscillation axis 84 is fixed to an initial value of 0°. On the other hand, in a state in which the diurnal axis 81 and the azimuth axis 83 are closer than a predetermined range, for example, when the altitude of Polaris 912 exceeds 70°, the control mode is switched to the azimuth axis fixed mode. In addition, in a state in which the diurnal axis 81 and the azimuth axis 83 are farther apart than a predetermined range, for example, when the altitude of Polaris 912 falls below 70° again in the azimuth axis fixed mode, the control mode is switched to the oscillation axis fixed mode.

[0034] The switching between the oscillation-axis-fixed mode and the azimuth-axis-fixed mode is not limited to being performed based on the angle between the diurnal axis 81 and the azimuth axis 83. For example, the switching between the oscillation-axis-fixed mode and the azimuth-axis-fixed mode may be performed so that the angular velocity or angular acceleration of the rotation around the diurnal axis 81 or the azimuth axis 83 is less than a predetermined value. In addition, the switching between the oscillation-axis-fixed mode and the azimuth-axis-fixed mode may be performed using both the angle between the diurnal axis 81 and the azimuth axis 83 and the angular velocity or angular acceleration of the rotation around the diurnal axis 81 or the azimuth axis 83.

[0035] In order to smoothly switch between these modes, it is preferable to provide a transition mode having angular velocities for both the azimuth axis 83 and the oscillation axis 84 so that the angular velocity around the azimuth axis 83 is gradually decelerated when switching from the fixed oscillation axis mode to the fixed azimuth axis mode, and the angular velocity around the oscillation axis 84 is gradually decelerated when switching from the fixed azimuth axis mode to the fixed oscillation axis mode. It is also preferable that the angle around the oscillation axis 84 is gradually returned to the initial value of 0° when switching from the fixed azimuth axis mode to the fixed oscillation axis mode. Depending on the state of control, the angle to be taken around the oscillation axis 84 may exceed, for example, ±30°, which is the limit of the device. In that case, the angle around the oscillation axis 84 is fixed at its maximum value, and the control mode is switched to the fixed oscillation axis mode. In this case, it is also preferable to gradually reduce the angular velocity around the oscillation axis 84 to stop the rotation before reaching ±30°.

[0036] An example of the control in this embodiment will be described with reference to the flowchart shown in FIG.

[0037] In step S1, the control device 4 controls the operation of the optical planetarium 10 in a fixed oscillation axis mode. That is, the control device 4 fixes the angle around the oscillation axis 84, and calculates the angles around the diurnal axis 81, the latitudinal axis 82, and the azimuth axis 83 to reproduce the target starry sky. The control device 4 controls the rotation around the diurnal axis 81, the latitudinal axis 82, and the azimuth axis 83 based on the obtained values.

[0038] In step S2, the control device 4 judges whether the angle between the daily axis 81 and the horizontal plane is greater than a predetermined first value, for example, 70°. If the angle between the daily axis 81 and the horizontal plane is not greater than the first value, the process returns to step S1, and control in the fixed oscillation axis mode is continued. On the other hand, if the angle between the daily axis 81 and the horizontal plane is greater than the first value, the process proceeds to step S3.

[0039] In step S3, the control device 4 controls the operation of the optical planetarium 10 in the transition mode in order to transfer the control of the operation of the optical planetarium 10 to the azimuth axis fixed mode. That is, the control device 4 determines the angle around the azimuth axis 83 so as to gradually decrease the angular velocity of the rotation around the azimuth axis 83, and calculates the angles around the diurnal axis 81, the latitudinal axis 82, and the oscillation axis 84 to reproduce the target starry sky based on the angle around the azimuth axis 83. The control device 4 controls the rotation around the diurnal axis 81, the latitudinal axis 82, the azimuth axis 83, and the oscillation axis 84 based on the obtained values.

[0040] In step S4, the control device 4 determines whether the angular velocity of the rotation around the azimuth axis 83 has become 0, that is, whether the rotation around the azimuth axis 83 has stopped. If the rotation around the azimuth axis 83 has not stopped, the process returns to step S3, and control in the transition mode continues. On the other hand, if the rotation around the azimuth axis 83 has stopped, the process proceeds to step S5.

[0041] In step S5, the control device 4 controls the operation of the optical planetarium 10 in the azimuth axis fixed mode. That is, the control device 4 fixes the angle of the azimuth axis 83 while the rotation around the axis 83 is stopped, and calculates angles around the diurnal axis 81, the latitudinal axis 82, and the oscillation axis 84 to reproduce the target starry sky. The control device 4 controls the rotation around the diurnal axis 81, the latitudinal axis 82, and the oscillation axis 84 based on the obtained values.

[0042] In step S6, the control device 4 makes a decision as to whether or not to limit the rotation around the oscillation axis 84. There is a limit that the rotation around the oscillation axis 84 can only be ±30°, for example. For this reason, if the angle around the oscillation axis 84 is likely to reach ±30°, for example, the azimuth axis fixed mode cannot be continued, and a transition to the oscillation axis fixed mode must be made. Therefore, the control device 4 judges whether or not the angle around the oscillation axis 84 is likely to reach ±30°, for example. For example, the control device 4 compares the current angle around the oscillation axis 84 with a limit value, the absolute value of which is set to a smaller value as the current angular velocity around the oscillation axis 84 is faster, and decides to limit the rotation around the oscillation axis 84 when the current angle around the oscillation axis 84 exceeds the limit value.

[0043] In step S7, the control device 4 determines whether or not to limit the rotation about the oscillation shaft 84 based on the decision made in step S6. When the rotation about the oscillation shaft 84 is to be limited, the process proceeds to step S9. On the other hand, when the rotation about the oscillation shaft 84 is not to be limited, the process proceeds to step S8.

[0044] In step S8, the control device 4 judges whether the angle between the diurnal axis 81 and the horizontal plane is smaller than a predetermined second value, such as 70°. If the angle between the diurnal axis 81 and the horizontal plane is not smaller than the second value, the process returns to step S5, and control in the azimuth axis fixed mode continues. On the other hand, if the angle between the diurnal axis 81 and the horizontal plane is smaller than the second value, the process proceeds to step S9. Note that the second value may be set to a value smaller than the first value so as to prevent frequent repeated switching between the oscillation axis fixed mode and the azimuth axis fixed mode.

[0045] In step S9, the control device 4 controls the operation of the optical planetarium 10 in the transition mode in order to shift the control of the operation of the optical planetarium 10 to the oscillation axis fixed mode. That is, the control device 4 determines the angle around the oscillation axis 84 so as to gradually decrease the angular velocity of the rotation around the oscillation axis 84 while moving the angle around the oscillation axis 84 toward the target value, and calculates the angles around the diurnal axis 81, the latitudinal axis 82, and the azimuth axis 83 to reproduce the target starry sky based on the angle around the oscillation axis 84. The control device 4 controls the rotation around the diurnal axis 81, the latitudinal axis 82, the azimuth axis 83, and the oscillation axis 84 based on the obtained values. Here, if it is determined in step S7 that the rotation around the oscillation axis 84 is about to reach its limit, the target value of the angle around the oscillation axis 84 becomes the limit value, for example, ±30°. On the other hand, if it is determined in step S8 that the angle between the daily axis 81 and the horizontal plane is smaller than the second value, the target value of the angle around the oscillation axis 84 becomes 0°, which is the initial state.

[0046] In step S10, the control device 4 judges whether the angular velocity of the rotation around the oscillation axis 84 is 0 and the angle around the oscillation axis 84 has reached the target value, that is, whether the rotation around the oscillation axis 84 has stopped at the target value. When the rotation around the oscillation axis 84 has not stopped at the target value, the process returns to step S9, and control in the transition mode is continued. On the other hand, when the rotation around the oscillation axis 84 has stopped at the target value, the process returns to step S1, and control in the oscillation axis fixed mode is performed again. Note that, when the angle around the oscillation axis 84 is fixed at, for example, ±30° and controlled in the oscillation axis fixed mode, when the angle between the diurnal axis 81 and the horizontal plane becomes sufficiently small, the angle around the oscillation axis 84 is gradually returned to 0°. The above operations are repeated.

[0047] Here, an example is shown in which the angle between the diurnal axis 81 and the horizontal plane is controlled to be prevented from becoming larger than a predetermined value, i.e., the angle between the diurnal axis 81 and the azimuth axis 83 is controlled to be prevented from becoming smaller than a predetermined value, but the control method is not limited to this. Similarly, the angles around the diurnal axis 81, the latitudinal axis 82, the azimuth axis 83, and the oscillation axis 84 may be controlled so as to suppress the angular velocity or angular acceleration of the rotation around the diurnal axis 81 or the azimuth axis 83 to be less than a predetermined value. That is, the oscillation axis fixed mode and the azimuth axis fixed mode may be switched depending on the angular velocity or angular acceleration of the rotation around the diurnal axis 81 or the azimuth axis 83. In this case, the same effect can be obtained.

[0048] The behavior of a conventional modern three-axis optical planetarium 110 and the behavior of the new four-axis optical planetarium 10 according to this embodiment when reproducing the diurnal motion of the starry sky 11,000 years from the present, as described with reference to FIG. 3, will be described below.

[0049] 5A is a diagram showing the angles around the diurnal axis 181, the latitudinal axis 182, and the azimuth axis 183 versus elapsed time when reproducing this diurnal motion using a conventional modern three-axis optical planetarium 110. Around 140 seconds, when the angle around the latitudinal axis 182 is close to 90°, this is when Polaris 912 passes near the zenith 913. It can be seen that the rotation around the diurnal axis 181 and the rotation around the azimuth axis 183 suddenly speeds up around the time when Polaris 912 passes near the zenith 913.

[0050] On the other hand, Fig. 5B is a diagram showing angles around the diurnal axis 81, the latitudinal axis 82, the azimuth axis 83, and the oscillation axis 84 with respect to elapsed time when a similar diurnal motion is reproduced using the new four-axis optical planetarium 10 of this embodiment. As in the case of Fig. 5A, the time around 140 seconds is when Polaris 912 passes near the zenith 913. According to the new four-axis optical planetarium 10 of this embodiment, even in a situation where Polaris 912 passes near the zenith 913, the rotation around the diurnal axis 81 and the rotation around the azimuth axis 83 do not suddenly become faster, and it can be seen that the rotation around each axis is smooth even in other situations.

[0051] As described above, the new four-axis optical planetarium 10 according to this embodiment can operate in two modes: a fixed oscillation axis mode and a fixed azimuth axis mode. In the fixed azimuth axis mode, the optical planetarium 10 can move Polaris smoothly near the zenith by combining rotation around the oscillation axis 84 and rotation around the latitude axis 82, and does not cause problems related to singular points. This allows the optical planetarium 10 to smoothly and appropriately reproduce the movement of the stars without causing a sudden increase in the rotation speed around an axis such as the diurnal axis 81 or the azimuth axis 83, which may occur only in the fixed oscillation axis mode.

[0052] In order to reproduce any starry sky smoothly and appropriately, the number of rotatable axes should be increased, and as described above, a similar effect can be obtained with the classical four-axis system. On the other hand, as described above, the size of the device is large in the classical four-axis optical planetarium 210. In contrast, in the optical planetarium 10 of the new four-axis system according to this embodiment, the oscillating axis 84 can be added by making the frame fork 22 into an arc shape and attaching roller bearings along the arc rail. Therefore, the optical planetarium 10 as a whole does not become larger. According to this embodiment, a small and lightweight optical planetarium 10 can be realized, similar to the modern three-axis system, despite being a four-axis system.

[0053] There are other methods of adding an axis to a modern three-axis optical planetarium. For example, it is possible to add an axis so that the azimuth axis can be swung by tilting the entire device above the pedestal. However, such a configuration requires an azimuth axis tilt angle changing mechanism to be provided on the pedestal, which increases the size of the device. Therefore, in this embodiment, the azimuth axis is fixed vertically and the latitude axis is made tiltable, making the device a four-axis type. In particular, as in the above embodiment, it is preferable for the latitude axis tilt angle changing mechanism 40 to have the following configuration in order to reduce the size of the device. That is, the swing axis 84 around which the latitude axis 82 rotates is provided so as to pass through the center of the star sphere 11 perpendicularly to the azimuth axis 83 and the latitude axis 82. The stand fork 22 that supports the star sphere 11 rotatably around the latitude axis 82 is provided on a plane including the latitude axis 82 and the azimuth axis 83. The latitudinal axis inclination angle changing mechanism 40 has a configuration in which a slider 43 that slides on a rail 41 that is provided in an arc shape with the swing axis 84 as its center is provided on the frame fork 22 .

[0054] Here, the case of reproducing the starry sky at a point of 37° north latitude 11,000 years in the future has been described as an example, but the same applies when reproducing the movements of other celestial bodies. That is, when Polaris, which is located near the diurnal axis, passes near the zenith or passes directly below, the modern three-axis system causes a similar problem, whereas the new four-axis system of this embodiment can avoid this problem. The optical planetarium 10 of the new four-axis system of this embodiment operates in the same way under various conditions, such as when projecting the starry sky as seen from space, and can always achieve appropriate projection of the starry sky in these cases.

[0055] Although the present invention has been described above by showing preferred embodiments, it goes without saying that the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention. [Explanation of symbols]

[0056] 1 Planetarium System 2 Screens 3. Dome 4. Control device 10 Optical Planetarium 11 Stellar sphere 11a Hokuten projector 11b Southern sky projector 12 Projector 21 Diurnal axis support mechanism 22 Mounting fork 23 Latitude axis support mechanism 25 Azimuth axis support mechanism 26 Support part 27 Pedestal 40 Latitude axis tilt angle change mechanism 41 Rail 43 Slider 45 Rack Gear 47 Pinion gear 49 Swing shaft motor 81 diurnal axis 82 Latitude Axis 83 Azimuth axis 84 Swing shaft

Claims

1. a projector for projecting star images; a diurnal axis support mechanism configured to allow the projector to rotate around a diurnal axis; a latitudinal axis support mechanism configured to allow the projector to rotate around a latitudinal axis perpendicular to the diurnal axis; an azimuth axis support mechanism configured to enable the projector to rotate around a vertical azimuth axis; a latitudinal axis inclination angle changing mechanism configured to change the angle between the latitudinal axis and a horizontal plane within a predetermined range; Equipped with The latitude axis tilt angle changing mechanism is provided on the azimuth axis support mechanism. Optical planetarium.

2. 2. The optical planetarium according to claim 1, wherein the latitudinal axis tilt angle changing mechanism is configured to enable the latitudinal axis to rotate around a swing axis perpendicular to the azimuth axis and the latitudinal axis.

3. The optical planetarium according to claim 2 , wherein the rocking axis passes through the center of the projector.

4. The latitude axis tilt angle changing mechanism is A rail provided in an arc shape centered on the swing shaft; A slider that slides on the rail; The optical planetarium according to claim 2 or 3, comprising:

5. An optical planetarium according to any one of claims 2 to 4, a control device for controlling angles around the diurnal axis, the latitude axis, the azimuth axis, and the oscillation axis; A planetarium system comprising:

6. The control device includes: a fixed oscillation axis mode in which angles around the oscillation axis are specified and angles around the diurnal axis, the latitudinal axis, and the azimuth axis are calculated; a fixed azimuth axis mode in which an angle around the azimuth axis is specified and angles around the diurnal axis, the latitude axis, and the oscillation axis are calculated; and controlling the operation of the optical planetarium by switching between the oscillation axis fixed mode and the azimuth axis fixed mode. The planetarium system according to claim 5 .

7. The planetarium system of claim 6, wherein the control device limits the angle around the oscillation axis to within a predetermined range in the fixed azimuth axis mode, and switches the control mode to the fixed oscillation axis mode before the angle around the oscillation axis exceeds the predetermined range.

8. The planetarium system according to any one of claims 5 to 7, wherein the control device controls the angles around the diurnal axis, the latitudinal axis, the azimuth axis, and the oscillation axis so that the angle between the diurnal axis and the azimuth axis is greater than a predetermined value.

9. The control device controls the angles around the diurnal axis, the latitudinal axis, the azimuth axis, and the swing axis so that the angular velocity or angular acceleration of rotation around the diurnal axis or the azimuth axis is less than a predetermined value. A planetarium system according to any one of claims 5 to 8.

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