Optical planetarium and planetarium system having the same

Abstract

An optical planetarium includes: a projector that projects star images; a diurnal axis support mechanism configured to enable the projector to rotate about the diurnal axis; a declination axis support mechanism configured to enable the projector to rotate about a declination axis orthogonal to the diurnal axis; an azimuth axis support mechanism configured to enable the projector to rotate about a vertically provided azimuth axis; and a declination axis tilt angle change mechanism configured to be able to change the angle formed by the declination axis and the horizontal plane within a specified range.

Description

Technical Field

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

[0002] 1. Modern three-axis

[0003] exist Figure 6 1 shows the structure of a representative optical planetarium which is currently the most popular. In the optical planetarium 110, as projectors 112 for projecting stars, hemispherical projectors 111a for the north sky and 111b for the south sky are respectively arranged opposite to each other. The projectors 111a for the north sky and 111b for the south sky are called star balls 111. The star balls 111 can rotate around a diurnal axis 181. The star balls 111 are supported on a stand fork 122 so as to be rotatable around a horizontally arranged latitude axis 182 which is orthogonal to the diurnal axis 181. By rotating the star balls 111 around the latitude axis 182, the inclination angle of the diurnal axis 181 with respect to the horizontal plane can be freely changed.

[0004] The stars projected from the star sphere 111 are arranged in coordinates based on equatorial coordinates with the earth's rotation axis as a reference so that the diurnal axis 181 points to the current celestial north pole and celestial south pole. Therefore, the diurnal motion of the stars is reproduced on the dome by rotating the star sphere 111 around the diurnal axis 181. In addition, by rotating the star sphere 111 around the latitude axis 182, the optical planetarium 110 can reproduce the starry sky at an observation point at any latitude on the earth.

[0005] In recent years, in planetariums, the method of arranging the audience seats in one direction instead of the method of arranging the audience seats in concentric circles toward the center of the dome as in the past has become the mainstream. With such a configuration, it is easy to adjust the sight lines of the commentator and the audience to the same direction, so it is easy for the commentator to correctly convey the explanation of the celestial body to all the audience. On the other hand, since a specific direction is taken as the front, it is difficult to see the side opposite to the front. For example, when the south side is taken as the front, in order to explain the celestial body on the north side, the commentator and the audience must look back and look directly behind. This would be inconvenient, so the optical planetarium 110 is provided with an azimuth axis 183 that rotates the entirety in the horizontal direction. Such a method of freely changing the front direction is becoming popular. As mentioned above, in recent years, in order to reproduce the movement of celestial bodies such as stars, an optical planetarium 110 having three axes, a daily axis 181, a latitude axis 182, and an azimuth axis 183, is generally used. Such a method of optical planetarium 110 is called a modern three-axis method.

[0006] 2. Traditional four-axis

[0007] In the past, in order to reproduce the change in the Earth's axis of rotation over many years, known as precession, an optical planetarium 210 such as that shown in Figure 7 was generally used. This optical planetarium 210 had, in addition to the diurnal axis 281 and the latitude axis 282, a precession axis 285. This method of the optical planetarium 210 is called the traditional three-axis type. The north celestial sphere 211a and the south celestial sphere 211b are configured to project the starry sky based on ecliptic coordinates with the Earth's orbital plane around the Sun rather than the Earth's axis of rotation as the reference. They are configured to be able to rotate about the precession axis 285. The precession axis 285 is held by a precession axis cage 291, and the entire precession axis cage 291 can rotate about the diurnal axis 281. The precession axis cage 291 maintains the angle formed by the diurnal axis 281 and the precession axis 285 at approximately 23.4°. This angle is the inclination angle of the Earth's equator with respect to the ecliptic plane. The diurnal axis 281 is held by the latitude axis 282, and by rotating the latitude axis 282, the starry sky of an observation site at any latitude can be reproduced, which is the same as in the case of the modern three-axis type. By rotating the precession axis 285 of the traditional three-axis type optical planetarium 210, not only can the current motion of the stars with the current North Star (Polaris, α Ursae Minoris) as the North Star be reproduced, but also the motion of the stars with Vega in the Lyra constellation as the North Star 11,000 years from now can be reproduced, for example.

[0008] In addition, an optical planetarium 210 is also known that has an azimuth axis 283 for horizontally rotating the entire device on the basis of the traditional three-axis type. This method of the optical planetarium 210 is called the traditional four-axis type.

[0009] In the traditional three-axis type and traditional four-axis type optical planetariums 210, since the north celestial sphere 211a and the south celestial sphere 211b are inclinedly provided on the precession axis cage 291, the size of the device becomes large. The relatively large optical planetarium 210 sometimes obstructs the view of the audience. Therefore, in recent years, the traditional three-axis type and traditional four-axis type optical planetariums 210 are not often used, and the use of the modern three-axis type optical planetarium 110 has become the mainstream. According to the modern three-axis type, the celestial sphere 111 can be made compact, and the optical planetarium 110 does not obstruct the view of the audience.

[0010] For example, an optical planetarium of the above-mentioned existing type is disclosed in Japanese Patent Laid-Open No. 4-204586.

[0011] 3. Multi-axis synthesis control

[0012] In a modern three-axis optical planetarium 110, precession motion and the like cannot be reproduced by rotation about one axis or the like. Therefore, the angles of rotation about three axes are controlled by a computer, and precession motion and the like are virtually reproduced by a three-axis combined motion. By combining the rotations about the three axes, namely, the diurnal axis 181, the declination axis 182, and the azimuth axis 183, the star globe 111 can theoretically obtain all attitude angles. Therefore, by reliably controlling the angles of rotation about these three axes, not only precession motion is reproduced, but also rotational motion centered on an arbitrary point on the celestial sphere is reproduced. Thus, for example, the starry sky as viewed from a planet other than the Earth can also be reproduced. Summary of the Invention

[0013] In a multi-axis combined control using a modern three-axis type, when two axes such as the diurnal axis 181 and the azimuth axis 183 are close to each other, for example, when they overlap, the degree of freedom of motion decreases, and sometimes the reproduction of the starry sky cannot be appropriately performed. According to the combined motion of four axes based on a conventional four-axis type, such a decrease in the degree of freedom of motion can be prevented, and the starry sky can be reproduced with high accuracy. However, in the conventional four-axis type, compared with the modern three-axis type, the optical planetarium 210 becomes more complex and larger in size.

[0014] An object of the present invention is to make the device compact and appropriately reproduce a variety of starry skies in an optical planetarium.

[0015] According to one aspect of the present invention, an optical planetarium includes: a projector that projects star images; a diurnal axis support mechanism configured to enable the projector to rotate about the diurnal axis; a declination axis support mechanism configured to enable the projector to rotate about a declination axis orthogonal to the diurnal axis; an azimuth axis support mechanism configured to enable the projector to rotate about a vertically provided azimuth axis; and a declination axis tilt angle change mechanism configured to be able to change the angle formed by the declination axis and the horizontal plane within a specified range.

[0016] According to the present invention, in an optical planetarium, a variety of starry skies can be appropriately reproduced while making the device compact. Brief Description of the Drawings

[0017] Figure 1 It is a perspective view showing an outline of a structural example of an optical planetarium according to an embodiment.

[0018] Figure 2 It is a schematic view showing an outline of a structural example of a planetarium system according to an embodiment.

[0019] Figure 3 It is a diagram for explaining the case of the diurnal motion of the starry sky in the future 11,000 years from now.

[0020] Figure 4 It is a flowchart showing a control example of an optical planetarium according to an embodiment.

[0021] Figure 5A This is a diagram showing an example of the changes in angles around the diurnal axis, the latitude axis, and the azimuth axis in the case of reproducing the diurnal motion of the starry sky 11,000 years from now using a modern three-axis optical planetarium.

[0022] Figure 5B This is a diagram showing an example of the changes in angles around the diurnal axis, the latitude axis, the azimuth axis, and the swing axis in the case of reproducing the diurnal motion of the starry sky 11,000 years from now using a new four-axis optical planetarium according to an embodiment.

[0023] Figure 6 This is a perspective view showing an outline of a structural example of a modern three-axis optical planetarium.

[0024] Figure 7 This is a perspective view showing an outline of a structural example of a conventional four-axis optical planetarium. Detailed Embodiment

[0025] [Structure of Optical Planetarium]

[0026] An embodiment will be described with reference to the accompanying drawings. The optical planetarium of this embodiment is an optical planetarium of a four-axis projector in which a swing axis for tilting the latitude axis within a certain range is provided on a modern three-axis optical planetarium. By having four axes, it is also possible to appropriately reproduce the precession motion and the rotational motion centered on an arbitrary point on the celestial sphere such as the starry sky viewed from a planet other than the Earth. In addition, according to the structure of this embodiment, the device can be made compact. The mode of the optical planetarium of this embodiment is called the new four-axis type.

[0027] In Figure 1 an outline of a structural example of the optical planetarium 10 of this embodiment is shown. As Figure 1 shown, the optical planetarium 10 of this embodiment is equipped with a projector 12 for projecting star images in the same way as the existing modern three-axis optical planetarium 110. In Figure 1 the example shown, the projector 12 includes a celestial globe 11, and the celestial globe 11 includes a north-sky projector 11a and a south-sky projector 11b that are respectively hemispherical and mounted facing each other. The celestial globe 11 is supported by a diurnal axis support mechanism 21 so as to be rotatable about the diurnal axis 81. The diurnal axis support mechanism 21 includes, for example, a shaft member along the diurnal axis 81, a bearing for receiving the shaft member, a motor and a speed reducer for rotating the shaft member, an encoder for detecting the rotation angle, etc. The structure of the diurnal axis support mechanism 21 is not limited to this and can be any structure. For example, the diurnal axis support mechanism 21 can also be formed using an annular track and a slider provided at the peripheral portion of a circular plate that slides relative to the track, etc.

[0028] The globe 11 is supported on the gantry fork 22 by a latitude axis support mechanism 23 in such a manner as to be able to rotate about a latitude axis 82 orthogonal to the diurnal axis 81. The latitude axis support mechanism 23 can also adopt various structures, for example, including a shaft member, bearings, a motor, a speed reducer, an encoder, etc. The optical planetarium 10 is configured such that by rotating the globe 11 about the latitude axis 82, the inclination angle between the diurnal axis 81 and the horizontal plane can be freely changed.

[0029] Similar to the existing modern three-axis optical planetarium 110, the stars projected from the globe 11 are arranged in coordinates based on the equatorial coordinates with the earth's axis of rotation as a reference. By rotating the globe 11 about the diurnal axis 81, the diurnal motion of the stars is reproduced on the dome screen. In addition, by rotating the globe 11 about the horizontal latitude axis 82, the starry sky at an observation site at any latitude on the earth is reproduced.

[0030] In addition, the optical planetarium 10 is configured to rotate about a vertically provided azimuth axis 83 in such a manner that its whole body rotates in the horizontal direction. That is, the gantry fork 22 is supported by an azimuth axis support mechanism 25 in such a manner as to be able to rotate about the azimuth axis 83 relative to a base 27 fixed to the ground. The azimuth axis support mechanism 25 can also adopt various structures, for example, including a shaft member, bearings, a motor, a speed reducer, an encoder, etc. By rotating the gantry fork 22 about the azimuth axis 83, the azimuth 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 globe 11.

[0031] The optical planetarium 10 of the present embodiment further includes a latitude axis inclination angle change mechanism 40 configured to be able to change the angle formed by the latitude axis 82 and the horizontal plane within a specified range. In particular, in the optical planetarium 10 of the present embodiment, a swing axis 84 is provided so as to rotate the latitude axis 82. The swing axis 84 is arranged to be orthogonal to the azimuth axis 83 and the latitude axis 82 at the center of the globe 11.

[0032] In order to enable the declination axis 82 to rotate about the swing axis 84, the mounting fork 22 of the present embodiment has an arc shape centered on the center of the celestial globe 11. An arc-shaped track 41 centered on the center of the celestial globe 11 is provided on the support portion 26 that rotates about the azimuth axis 83 and is provided on the azimuth axis support mechanism 25. The mounting fork 22 has a slider 43 that slides on the track 41. The mounting fork 22 is supported on the support portion 26 of the azimuth axis support mechanism 25 via the track 41 and the slider 43. It is preferable to provide crossed roller bearings in parts of the track 41 and the slider 43. An arc-shaped rack 45 is provided on the mounting fork 22 along the arc-shaped track 41 and the slider 43, and a pinion 47 for driving the rack 45 is provided on the support portion 26. The pinion 47 is driven by a swing axis motor 49. The tilt angle of the mounting fork 22 is freely controlled by the operation of the swing axis motor 49. The structure of the declination axis tilt angle changing mechanism 40 described here is an example, and as long as it has the same function, the declination axis tilt angle changing mechanism 40 can also use other structures. The movable range of the mounting fork 22 about the swing axis 84 is not limited to this, for example, it is ±30°. In this case, the celestial globe 11 can rotate within a range of ±30° about the swing axis 84 passing through the center of the celestial globe 11.

[0033] As Figure 2 shown, in the planetarium system 1 of the present embodiment, the optical planetarium 10 as described above is disposed at the center of the hemispherical dome 3 whose inner surface forms a screen 2. The optical planetarium 10 projects an image of a star 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 the control device 4. This control also includes the rotation of the celestial globe 11 about the diurnal axis 81, the declination axis 82, the azimuth axis 83, and the swing axis 84. The control device 4 includes a computer. The control device 4 includes integrated circuits such as a central processing unit (CPU), an application specific integrated circuit (ASIC), or a field programmable gate array (FPGA). In addition, the control device 4 includes a read only memory (ROM), a random access memory (RAM), a storage device, an input device, a display device, various interfaces, etc. The control device 4 operates according to a program or hardware.

[0034] [Operation of the optical planetarium]

[0035] While referring to Figure 6The operation of the existing modern three-axis optical planetarium 110 will be compared, and the operation of the new four-axis optical planetarium 10 of the present embodiment will be described while doing so.

[0036] In the globe 11 of the new four-axis optical planetarium 10 of the present embodiment, and in the globe 111 of the existing modern three-axis optical planetarium 110, the stars are arranged in coordinates based on the equatorial coordinates with the current Earth's axis of rotation as the reference. That is, for example, stars located at the current celestial north pole are arranged on the diurnal axis 81 of the north celestial projector 11a. Specifically, although there is an offset of less than 1°, the North Star (Polaris: α Ursae Minoris) is located near the celestial north pole, that is, near the diurnal axis 81 of the north celestial projector 11a.

[0037] As an example, consider the case of reproducing the diurnal motion of the starry sky 11,000 years into the future from the present. At this time, in the northern sky, although it does not exactly coincide with the celestial north pole, Vega in the constellation Lyra is located near the celestial north pole. When observed from a location near 37° north latitude, as Figure 3 shown, Vega 911 appears to be almost stationary in the northern sky at an altitude of approximately 37°. Since Polaris 912 is separated from Vega 911 by approximately 52°, Polaris 912 rises from the northeast sky and passes through a position approximately 1° north of the zenith 913 near the zenith. Other stars also perform diurnal motion centered on Vega 911.

[0038] In reality, even today, Polaris does not exactly coincide with the celestial north pole, and Vega will not exactly coincide with the celestial north pole 11,000 years into the future either. However, here, for the sake of explanation, it is assumed that Polaris coincides with the celestial north pole today, and Vega coincides with the celestial north pole 11,000 years into the future and Polaris passes near the zenith.

[0039] Consider the case of using the existing modern three-axis optical planetarium 110 to reproduce the motion of the starry sky at a location 37° north latitude 11,000 years into the future through the combined motion of three axes. At this time, the orientation of the diurnal axis 181 of the optical planetarium 110 indicates 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 separated from the zenith 913, the angular velocity around the azimuth axis 183 is small and no problem occurs.

[0040] However, although the speed of the diurnal motion is not so fast, when Polaris 912 passes near the zenith 913, as Figure 3As shown by the arrow, the azimuth of Beichen 912 changes sharply, so the rotation around the azimuth axis 183 must also be high-speed. When Beichen 912 completely passes through the zenith 913, its speed instantaneously becomes infinite. This is called a singular point. The approach of Beichen 912 to the zenith 913 means that the angle formed by the diurnal axis 181 and the azimuth axis 183 becomes smaller. When the horizon altitude of Beichen 912 is set to a°, the angle formed by the diurnal axis 181 and the azimuth axis 183 is (90 - a)°. In other words, the phenomenon occurring at the singular point is caused by the overlap of the azimuth axis 183 and the diurnal axis 181 and the decrease in the degree of freedom of movement. This phenomenon is the same as the so-called gimballock state. In the operation of the actual optical planetarium 110, there are limits to the maximum speed and maximum acceleration of the rotation around the rotation axis, so the optical planetarium 110 cannot accurately follow the ideal movement and causes unnatural movement.

[0041] According to the reference Figure 7 Regarding the conventional four-axis optical planetarium 210 described, this problem can be solved by the combined movement of the four axes. However, the size of the conventional four-axis optical planetarium 210 becomes larger, and there are cases where the optical planetarium 210 obstructs the view of the audience.

[0042] In response to this, in the new four-axis optical planetarium 10 of the present embodiment, by controlling the rotation around the four axes of the diurnal axis 81, the latitude axis 82, the azimuth axis 83, and the swing axis 84, it is possible to avoid the diurnal axis 81 and the azimuth axis 83 from being too close, and it is possible to avoid the above problems occurring in the existing modern three-axis type.

[0043] The new four-axis optical planetarium 10 of the present embodiment has two control modes: the swing axis fixed mode and the azimuth axis fixed mode. In the swing axis fixed mode, the angle around the swing axis 84 is fixed to a specified value, the angles around the diurnal axis 81, the latitude axis 82, and the azimuth axis 83 are calculated, and the attitude of the celestial globe 11 is controlled. When the angle around the swing axis 84 is 0° and the latitude axis 82 becomes horizontal, this is the same as the case of the existing modern three-axis type. In the azimuth axis fixed mode, the azimuth axis 83 is fixed to a specified value, the angles around the diurnal axis 81, the latitude axis 82, and the swing axis 84 are calculated, and the attitude of the celestial globe 11 is controlled. In each mode, it is known that the angles around each axis can be calculated mathematically using matrix calculations, etc. Here, the description of this calculation is omitted.

[0044] Normally, control is performed in a swing axis fixed mode with an angle fixed position around the swing axis 84 as the initial value of 0°. On the other hand, for example, when the altitude of the North Star 912 exceeds 70°, etc., in a state where the declination axis 81 and the azimuth axis 83 are closer than the specified range, the control mode is switched to the azimuth axis fixed mode. In addition, in the azimuth axis fixed mode, for example, when the altitude of the North Star 912 becomes lower than 70° again, etc., in a state where the declination axis 81 and the azimuth axis 83 are separated from the specified range, the control mode is switched to the swing axis fixed mode.

[0045] The switching between the swing axis fixed mode and the azimuth axis fixed mode is not limited to being based on the angle formed by the declination axis 81 and the azimuth axis 83. For example, the switching between the swing axis fixed mode and the azimuth axis fixed mode can also be performed in such a way that the angular velocity or angular acceleration of the rotation around the declination axis 81 or around the azimuth axis 83 is less than a specified value. In addition, both the angle formed by the declination axis 81 and the azimuth axis 83 and the angular velocity or angular acceleration of the rotation around the declination axis 81 or around the azimuth axis 83 can be used to perform the switching between the swing axis fixed mode and the azimuth axis fixed mode.

[0046] In order to smoothly perform the switching of this mode, it is preferable to set a mode of changing the angular velocity for both the azimuth axis 83 and the swing axis 84, so that when switching from the swing axis fixed mode to the azimuth axis fixed mode, the angular velocity around the azimuth axis 83 gradually decelerates, and when switching from the azimuth axis fixed mode to the swing axis fixed mode, the angular velocity around the swing axis 84 gradually decelerates. In addition, when switching from the azimuth axis fixed mode to the swing axis fixed mode, it is preferable that the angle around the swing axis 84 slowly returns to 0° as the initial value. In addition, depending on the state of control, the angle that should be taken around the swing axis 84 may exceed, for example, ±30° which is the limit of the device. In this case, the angle around the swing axis 84 is fixed at its maximum value, and the control mode is switched to the swing axis fixed mode. In this case, it is preferable to gradually reduce the angular velocity around the swing axis 84 and stop the rotation before reaching ±30°.

[0047] Refer to Figure 4 An example of the control of this embodiment will be described with reference to the flowchart shown.

[0048] In step S1, the control device 4 controls the operation of the optical planetarium 10 in the swing axis fixed mode. That is, the control device 4 fixes the angle around the swing axis 84 and calculates the angles around the declination axis 81, the latitude axis 82, and the azimuth axis 83 for reproducing the target starry sky. The control device 4 controls the rotation around the declination axis 81, the latitude axis 82, and the azimuth axis 83 based on the obtained values.

[0049] In step S2, the control device 4 determines whether the angle formed by the meridian axis 81 and the horizontal plane is greater than a specified first value, such as 70°. When the angle formed by the meridian axis 81 and the horizontal plane is not greater than the first value, the process returns to step S1, and the control in the swing axis fixed mode continues. On the other hand, when the angle formed by the meridian axis 81 and the horizontal plane is greater than the first value, the process proceeds to step S3.

[0050] In step S3, in order to transfer the control of the operation of the optical planetarium 10 to the azimuth axis fixed mode, the control device 4 controls the operation of the optical planetarium 10 in a transition mode. That is, the control device 4 determines the angle around the azimuth axis 83 in such a way that the angular velocity of the rotation around the azimuth axis 83 gradually decreases, and based on the angle around the azimuth axis 83, calculates the angles around the meridian axis 81, the latitude axis 82, and the swing axis 84 for reproducing the target starry sky. The control device 4 controls the rotations around the meridian axis 81, the latitude axis 82, the azimuth axis 83, and the swing axis 84 based on the obtained values.

[0051] In step S4, the control device 4 determines whether the angular velocity of the rotation around the azimuth axis 83 is 0, that is, whether the rotation around the azimuth axis 83 has stopped. When the rotation around the azimuth axis 83 has not stopped, the process returns to step S3, and the control in the transition mode continues. On the other hand, when the rotation around the azimuth axis 83 has stopped, the process proceeds to step S5.

[0052] 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 in the state where the rotation around the azimuth axis 83 has stopped, and calculates the angles around the meridian axis 81, the latitude axis 82, and the swing axis 84 for reproducing the target starry sky. The control device 4 controls the rotations around the meridian axis 81, the latitude axis 82, and the swing axis 84 based on the obtained values.

[0053] In step S6, the control device 4 makes a decision on whether to limit the rotation around the swing axis 84. There is a limit, for example, that the swing axis 84 can only rotate ±30°. Therefore, when the angle around the swing axis 84 reaches, for example, ±30°, the azimuth axis fixed mode cannot be continued, and thus it is necessary to switch to the swing axis fixed mode. Therefore, the control device 4 determines whether the angle around the swing axis 84 has reached, for example, ±30°. For example, the control device 4 compares the current angle around the swing axis 84 with a limit value that is set to a smaller absolute value as the current angular velocity around the swing axis 84 is faster, and when the current angle around the swing axis 84 exceeds the limit value, it is determined to limit the rotation around the swing axis 84.

[0054] In step S7, based on the determination made in step S6, the control device 4 determines whether to restrict the rotation about the swing axis 84. When restricting the rotation about the swing axis 84, the process proceeds to step S9. On the other hand, when not restricting the rotation about the swing axis 84, the process proceeds to step S8.

[0055] In step S8, the control device 4 determines whether the angle formed by the diurnal axis 81 and the horizontal plane is less than a specified second value, such as 70°. When the angle formed by the diurnal axis 81 and the horizontal plane is not less than the second value, the process returns to step S5 to continue the control in the azimuth axis fixed mode. On the other hand, when the angle formed by the diurnal axis 81 and the horizontal plane is less than the second value, the process proceeds to step S9. It should be noted that in order not to finely and repeatedly switch between the swing axis fixed mode and the azimuth axis fixed mode, the second value can also be set to a value smaller than the first value.

[0056] In step S9, in order to transfer the control of the operation of the optical planetarium 10 to the swing axis fixed mode, the control device 4 controls the operation of the optical planetarium 10 in a mode change. That is, the control device 4 determines the angle about the swing axis 84 in such a way that the angle about the swing axis 84 faces the target value and the angular velocity of the rotation about the swing axis 84 gradually decreases, and based on the angle about the swing axis 84, calculates the angles about the diurnal axis 81, the latitude axis 82, and the azimuth axis 83 for reproducing the target starry sky. The control device 4 controls the rotation about the diurnal axis 81, the latitude axis 82, the azimuth axis 83, and the swing axis 84 based on the obtained values. Here, when it is determined in step S7 that the rotation about the swing axis 84 is about to reach the limit, the target value of the angle about the swing axis 84 becomes its limit value, for example, ±30°. On the other hand, in step S8, when it is determined that the angle formed by the diurnal axis 81 and the horizontal plane is less than the second value, the target value of the angle about the swing axis 84 becomes 0° in the initial state.

[0057] In step S10, the control device 4 determines whether the angular velocity of the rotation about the swing axis 84 becomes 0 and whether the angle about the swing axis 84 becomes the target value, that is, whether the rotation about the swing axis 84 stops at the target value. When the rotation about the swing axis 84 does not stop at the target value, the process returns to step S9 to continue the control in the mode change. On the other hand, when the rotation about the swing axis 84 stops at the target value, the process returns to step S1 to perform the control in the swing axis fixed mode again. It should be noted that when the angle about the swing axis 84 is fixed at, for example, ±30° and the control is performed in the swing axis fixed mode, when the angle formed by the diurnal axis 81 and the horizontal plane becomes small enough, the angle about the swing axis 84 gradually returns to 0°. The above actions are repeated.

[0058] Here, an example of control is shown in which the angle formed by the surface sidereal axis 81 and the horizontal plane is greater than a specified value, that is, in a manner to avoid the angle formed by the sidereal axis 81 and the azimuth axis 83 from being less than the specified value, but the control method is not limited to this. Similarly, the angles around the sidereal axis 81, the latitude axis 82, the azimuth axis 83, and the swing axis 84 can also be controlled in such a way that the angular velocity or angular acceleration of the rotation around the sidereal axis 81 or the azimuth axis 83 is suppressed to be less than a specified value. That is, the swing axis fixed mode and the azimuth axis fixed mode can also be switched according to the angular velocity or angular acceleration of the rotation around the sidereal axis 81 or the azimuth axis 83. The same effect can also be obtained in this case.

[0059] For the reproduction reference Figure 3 The behavior of the existing modern three-axis optical planetarium 110 and the behavior of the new four-axis optical planetarium 10 of the present embodiment are described in the case of reproducing the diurnal motion of the future starry sky 11,000 years from now as described above.

[0060] Figure 5A It is a diagram showing the angles around the sidereal axis 181, the latitude axis 182, and the azimuth axis 183 with respect to the elapsed time in the case of reproducing this diurnal motion using the existing modern three-axis optical planetarium 110. Around 140 seconds when the angle around the latitude axis 182 is close to 90°, the North Star 912 passes near the zenith 913. It can be seen that around when the North Star 912 passes near the zenith 913, the rotation around the sidereal axis 181 and the rotation around the azimuth axis 183 become extremely fast.

[0061] On the other hand, Figure 5B It is a diagram showing the angles around the sidereal axis 81, the latitude axis 82, the azimuth axis 83, and the swing axis 84 with respect to the elapsed time in the case of reproducing the same diurnal motion using the new four-axis optical planetarium 10 of the present embodiment. Similar to Figure 5A the case, around 140 seconds is when the North Star 912 passes near the zenith 913. According to the new four-axis optical planetarium 10 of the present embodiment, even in the situation where the North Star 912 passes near the zenith 913, the rotation around the sidereal axis 81 and the rotation around the azimuth axis 83 do not become extremely fast, and even in other situations, the rotation around each axis is smooth.

[0062] As described above, the optical planetarium 10 of the new four-axis type according to the present embodiment can operate in two modes: a swing-axis fixed mode and an azimuth-axis fixed mode. Moreover, according to the azimuth-axis fixed mode, the optical planetarium 10 can reasonably move the North Star near the zenith by a combination of rotation about the swing axis 84 and rotation about the latitude axis 82, without causing problems related to singular points. As a result, a sharp increase in the rotational speed about axes such as the diurnal axis 81 or the azimuth axis 83, which may occur only in the swing-axis fixed mode, is not caused, and the optical planetarium 10 can smoothly and appropriately reproduce the movement of the stars.

[0063] In order to smoothly and appropriately reproduce any starry sky, it is only necessary to increase the number of rotatable axes. Therefore, as described above, a similar effect can be obtained even with a conventional four-axis type. On the other hand, as described above, in the optical planetarium 210 of the conventional four-axis type, the size of the device becomes large. In contrast, in the optical planetarium 10 of the new four-axis type according to the present embodiment, the addition of the swing axis 84 can be achieved by forming the pedestal fork 22 in an arc shape and installing a roller bearing along the arc-shaped track. Therefore, it does not lead to an increase in the overall size of the optical planetarium 10. According to the present embodiment, although it is a four-axis type, a small and lightweight optical planetarium 10 can be realized in the same manner as in the case of a modern three-axis type.

[0064] In a modern three-axis optical planetarium, as a method of adding a single axis, other methods can also be considered. For example, it can also be considered to add a single axis in such a way that the whole above the base is tilted to enable the azimuth axis to swing. However, in such a structure, an azimuth-axis tilt angle changing mechanism is provided on the base, and the device becomes large. Therefore, in the present embodiment, the device is made into a four-axis type by vertically fixing the azimuth axis and enabling the latitude axis to tilt. In particular, as in the above-described embodiment, in terms of downsizing the device, it is preferable that the latitude-axis tilt angle changing mechanism 40 has the following structure. That is, the swing axis 84 around which the latitude axis 82 rotates is provided to be orthogonal to the azimuth axis 83 and the latitude axis 82 and pass through the center of the celestial sphere 11. The pedestal fork 22 that supports the celestial sphere 11 so as to be rotatable about the latitude axis 82 is provided in the plane including the latitude axis 82 and the azimuth axis 83. The latitude-axis tilt angle changing mechanism 40 has a structure in which a slider 43 that slides on an arc-shaped track 41 centered on the swing axis 84 is provided on the pedestal fork 22.

[0065] Here, the case of reproducing the starry sky at a location of 37° north latitude 11,000 years later has been described as an example, but the same applies when reproducing the movements of other celestial bodies. That is, when the North Star disposed near the diurnal axis passes near the zenith or directly below, the same problem occurs in the modern three-axis method. On the other hand, this problem can be avoided in the new four-axis method of the present embodiment. The optical planetarium 10 of the new four-axis method of the present embodiment operates similarly under various conditions such as when projecting the starry sky observed from space, and appropriate projection of the starry sky can always be achieved in these cases.

[0066] As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to the foregoing embodiments, and various modifications can of course be made within the scope of the present invention.

Claims

1. An optical planetarium, wherein, the optical planetarium includes: a projector that projects star images; a diurnal axis support mechanism configured to enable the projector to rotate about the diurnal axis; a declination axis support mechanism configured to enable the projector to rotate about a declination axis orthogonal to the diurnal axis; an azimuth axis support mechanism configured to enable the projector to rotate about a vertically provided azimuth axis; and a declination axis tilt angle change mechanism configured to be able to change the angle formed by the declination axis and the horizontal plane within a specified range.

2. The optical planetarium according to claim 1, wherein, the declination axis tilt angle change mechanism is configured to enable the declination axis to rotate about a swing axis orthogonal to the azimuth axis and the declination axis.

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

4. The optical planetarium according to claim 2 or 3, wherein, the declination axis tilt angle change mechanism includes: a track provided in an arc shape centered on the swing axis; and a slider that slides on the track.

5. A planetarium system, wherein, the planetarium system includes; the optical planetarium according to any one of claims 2 to 4; and a control device that controls the angles about the diurnal axis, the declination axis, the azimuth axis, and the swing axis.

6. The planetarium system according to claim 5, wherein, the control device has control modes of a swing axis fixed mode and an azimuth axis fixed mode, in the swing axis fixed mode, the angle about the swing axis is specified, and the angles about the diurnal axis, the declination axis, and the azimuth axis are calculated, in the azimuth axis fixed mode, the angle about the azimuth axis is specified, and the angles about the diurnal axis, the declination axis, and the swing axis are calculated, the control device controls the operation of the optical planetarium by switching between the swing axis fixed mode and the azimuth axis fixed mode.

7. The planetarium system according to claim 6, wherein, the control device limits the angle about the swing axis within a specified range in the azimuth axis fixed mode, and switches the control mode to the swing axis fixed mode before the angle about the swing axis exceeds the specified range.

8. The planetarium system according to any one of claims 5 to 7, wherein, the control device controls the angles about the diurnal axis, the declination axis, the azimuth axis, and the swing axis such that the angle formed by the diurnal axis and the azimuth axis is greater than a specified value.

9. The planetarium system according to any one of claims 5 to 7, wherein, the control device controls the angles about the diurnal axis, the declination axis, the azimuth axis, and the swing axis such that the angular velocity or angular acceleration of the rotation about the diurnal axis or the azimuth axis is less than a specified value.

Images