JP6704756B2 - Image projector and planetarium - Google Patents

Description

The present invention relates to an image projection device that projects an image on a screen, and a planetarium using the same. More specifically, the present invention relates to an image projection device and a planetarium that use a laser beam and generate an image by a diffraction phenomenon based on the laser beam and project the image.

As an example of a conventional image projection device, the one described in Patent Document 1 can be cited. In the image projection apparatus of the same document, a projected image is generated using a "transparent original plate" ([0010] etc. of the same document). By moving the transparent original plate, the projected image is changed. Specifically, the same document reproduces the diurnal motion of a star ([0012]) and the starry sky at different positions on the earth ([0013]) by moving the transparent original plate.

JP, 2006-308785, A

However, the above-mentioned conventional technique has a problem. By applying the technique of Patent Document 1 and providing two or more regions in the transmission original plate, two or more separate images can be switched and projected. However, when actually trying to do this, there were the following problems. That is, a halfway image is projected in the middle of image switching. A halfway image is a projected image in which the right half of one image appears in the left half of the projection area and the left half of the other image appears in the right half of the projection area. This is not the originally intended projection video, but a very amusing projection video from the viewpoint of the viewer. In order to prevent such an image from being projected, the light source is temporarily turned off during the switching of images. However, it also becomes an exciting production for the viewer.

The present invention has been made to solve the above-mentioned problems of the conventional technique. That is, the problem is to provide an image projection device and a planetarium that can project not only two or more separate images by switching, but also an individual image at the original projection position even during the switching of images. To provide.

The planetarium according to one embodiment of the present invention includes a laser oscillating unit that outputs a laser beam, and a diffractive optical element that is provided on the optical path of the laser beam output from the laser oscillating unit and that generates a diffraction image based on the diffraction of the laser beam. and an image projection apparatus that have a, and a dome screen, the image projection apparatus a facility for projector to project a diffraction image on the dome screen, the diffractive optical element, a first diffraction grating for generating a first diffractive image An area and a second diffraction grating area for generating a second diffraction image, and a projection mode switching unit for switching the mode of projection of the diffraction image by the diffractive optical element, and switching by the projection mode switching unit. The projection mode to be used is one image mode in which a diffraction image is projected using only one of the first diffraction grating region and the second diffraction grating region, and both the first diffraction grating region and the second diffraction grating region. It includes a superimposition image mode in which a diffraction image is projected by using it.

With the planetarium in the above aspect, it is possible to project the first diffraction image on the screen using only the first diffraction region of the diffractive optical element. It is also possible to project the second diffraction image on the screen using only the second diffraction region. These are the single image modes. Here, since the image projected on the screen is a diffractive image, the position of each image does not change from the original projected position even when the image to be projected is being switched. Therefore, it is possible to naturally switch the images without making the viewer feel uncomfortable. In addition, a superimposition image mode in which a diffracted image is projected using both the first diffraction area and the second diffraction area can be easily performed.

In the planetarium according to the above aspect, the projection mode switching unit further performs mode switching by moving the diffractive optical element in an in-plane direction intersecting the optical path of the laser light output from the laser oscillator. Preferably. Such movement of the diffractive optical element causes the projected diffraction image to disappear without moving the position, or causes the non-projected diffraction image to appear at the original position from the beginning. be able to.

When mode switching is performed by moving the diffractive optical element in this way, the first diffractive optical element moves from the first one image mode using the first diffractive grating area to the second diffractive grating area using the second image mode. By projecting the laser light over both the first diffraction grating region and the second diffraction grating region during the transition to the image mode, it is possible to project the superimposed image mode. In this way, the superimposition image mode can be realized with one laser beam. Further, the transition from the first one-image mode to the second one-image mode can be naturally performed while passing through the overlapping image mode on the way.

In the planetarium according to the above aspect, the laser oscillating portion may have a plurality of emitting portions from which laser light is emitted. In this case, the projection mode switching unit can switch the mode by switching which of the plurality of emitting units is used. Depending on the proper use of the emitting part, the projected diffraction image may disappear without moving the position, or the non-projected diffraction image may appear at the original position from the beginning. be able to.

In the case of having a plurality of emitting portions, it is preferable that some of the emitting portions are arranged at positions where the emitted laser light is applied across both the first diffraction grating region and the second diffraction grating region. .. In this case, the superimposition image mode can be executed by projecting the diffraction image by the one arranged at the position among the plurality of emitting portions.

In the planetarium according to any one of the above aspects, it is preferable that the laser oscillating unit emits a larger amount of light when the projection mode of the projection mode switching unit is the superimposition image mode than when the projection mode is the single image mode. By performing such light amount control, it is possible to prevent the viewer from being given the impression that the screen is dark in the superimposed image mode. The same applies when switching from one diffraction image to another.

Image projection apparatus according to another aspect of the present invention includes a laser oscillating unit, and a diffractive optical element, a device for projecting, the diffraction image on the screen, the diffractive optical element, the first diffraction image And a second diffraction grating region that generates a second diffraction image, and a projection mode switching unit that switches modes for projecting the diffraction image by the diffractive optical element. , A one-image mode in which only one of the first diffraction grating region and the second diffraction grating region is used to project a diffraction image in the projection mode switched by the projection mode switching unit, the first diffraction grating region, and the second diffraction mode. A superimposition image mode in which a diffraction image is projected using both the diffraction grating region is included, and the laser oscillating unit is in the single-image mode when the projection mode by the projection mode switching unit is the superimposition image mode. Ru der things to increase the amount of light than when.

According to this configuration, not only two or more separate images can be switched and projected, but also an image projection device and a planetarium that can project individual images to their original projection positions even during the switching of images are provided. ing.

It is a front view of the image projection apparatus according to the embodiment. FIG. 3 is a plan view of the diffractive optical element plate according to the embodiment. FIG. 6 is a schematic diagram illustrating formation of a diffractive image by the first region of the diffractive optical element plate according to the embodiment. FIG. 6 is a schematic diagram illustrating formation of a diffractive image by the second region of the diffractive optical element plate according to the embodiment. It is a schematic diagram which shows the condition which is projecting the 1st diffraction image by the diffractive optical element plate which concerns on embodiment. It is a schematic diagram which shows the condition which is projecting the 2nd diffraction image by the diffractive optical element plate which concerns on embodiment. It is a schematic diagram explaining the positional accuracy of the projected image by a diffractive optical element. (Comparative example) It is a schematic diagram for explaining the positional accuracy of the projected image by the transparent original plate. It is a schematic diagram which shows the irradiation condition of a laser beam to a diffractive optical element plate at the time of image switching. It is a schematic diagram which shows the projection of a diffraction image in the situation of FIG. (Comparative example) FIG. 6 is a schematic diagram showing a situation when switching a projected image by a transparent original plate. It is a schematic diagram which shows the example of the production of the projection by the image projection apparatus which concerns on embodiment. It is a top view of the diffractive optical element plate for performing the production of FIG. It is a block diagram showing a configuration of a control system of the image projection apparatus according to the embodiment. It is a schematic diagram of the image projection apparatus which concerns on a modification. It is a front view of the planetarium projection device using the image projection device according to the embodiment. It is a perspective view of a planetarium using the image projection device according to the embodiment. It is a top view which shows the example of arrangement (straight line shape) of the CGH area|region in a diffractive optical element plate. It is a top view which shows the example of arrangement|positioning (two-dimensional shape) of the CGH area|region in a diffractive optical element plate. It is a top view showing an example of arrangement (with a gap) of a CGH field in a diffractive optical element board.

Hereinafter, embodiments embodying the present invention will be described in detail with reference to the accompanying drawings. The image projection apparatus 1 according to this embodiment is configured as shown in FIG. The image projection apparatus 1 of FIG. 1 has a laser light source 2 and a diffractive optical element plate 3. The laser light source 2 is a laser oscillation unit that outputs a laser beam L. In the image projection apparatus 1 of this embodiment, the diffractive optical element plate 3 is arranged on the optical path of the laser light L output from the laser light source 2. Then, the projection space beyond the diffractive optical element plate 3 is irradiated with the diffracted laser light D obtained by diffracting the laser light L by the diffractive optical element plate 3. In the image projection device 1 of the present embodiment, the diffractive optical element plate 3 is further movable in the in-plane direction intersecting the optical path of the laser light L (arrow A).

The diffractive optical element plate 3 in this embodiment has a first region 4 and a second region 5, as shown in FIG. Both the first region 4 and the second region 5 are diffraction gratings in which a CGH (Computer Generated Hologram) pattern is formed (the diffraction grating itself is [0023] in JP2013-013912A or JP2013-2013A). See [0012] of 190394). The first area 4 and the second area 5 generate different diffraction images. Here, it is assumed that the first area 4 shows the Okuma constellation pattern (FIG. 3), and the second area 5 shows the Okuma constellation line group (FIG. 4) on the screen 6, respectively. Therefore, in the image projection apparatus 1 of this embodiment, the image projected on the screen 6 can be switched by moving the diffractive optical element plate 3 shown by the arrow A in FIG. FIG. 5 shows a situation in which the first diffraction image (constellation picture) is projected using the first region 4. FIG. 6 shows a situation in which the second diffraction image (mark line group) is projected using the second region 5.

It should be noted that the screen 6 in FIGS. 3 to 6 shows the projected image in black on a white background, but this is for convenience of drawing, and it should be noted that the brightness is reversed on the actual screen. That is, on the actual screen, the ground portion is dark, and a bright projected image appears in it. This is the same for all figures in which "Screen 6" appears below.

In this way, the image projection apparatus 1 of the present embodiment can switch and project two types of diffraction images. Here, there are two advantages described below. The first advantage is that the positional accuracy of the diffractive optical element plate 3 is not so required. The second advantage is that switching between the two images can be performed without making the viewer feel uncomfortable.

First, the first advantage will be described. This advantage is obtained because the principle of image formation is the diffraction phenomenon shown in FIG. That is, the irradiation direction of the diffracted laser light D by the diffractive optical element plate 3 is determined as the diffraction angle θ with respect to the irradiation direction of the original laser light L. The diffraction angle θ is determined only by the wavelength of the laser light L and the lattice constant of the diffractive optical element plate 3, and it does not matter at which position of the diffractive optical element plate 3 the laser light L is incident. Since the diffraction angle θ is constant in this way, the projected image is projected at a position apart from the incident position of the laser light L on the diffractive optical element plate 3 in the direction of the diffraction angle θ to some extent. Therefore, if the arrangement of the laser light source 2 is securely fixed, even if the precision of the stop position of the diffractive optical element plate 3 is poor, it does not affect the position of the projected image. It is sufficient that the irradiation range of the laser light L on the diffractive optical element plate 3 covers only one of the first region 4 and the second region 5 which is a target, and does not extend over the other.

If the position of the laser light source 2 is deviated as shown by an arrow B in FIG. 7, the amount of the deviation will be directly reflected on the position of the projected image. However, unlike conventional projectors that use lenses, this is not magnified by the optical system. That is, if the positional deviation of the laser light source 2 is on the millimeter level, the positional deviation of the projected image on the screen 6 is also on the millimeter level. Therefore, if the positional deviation of the laser light source 2 is within the range of the normal mounting accuracy, the positional deviation of the projected image is not perceived by the viewer.

This is a difference from the case of projecting an image by a conventional transparent original plate. When an image is projected on the screen 6 using the diffused light source 7 and the transmission original plate 8 as shown in FIG. 8, the positional deviation amount C of the transmission original plate 8 is reflected on the screen 6 after being greatly enlarged. It will be done (arrow E). Therefore, in this method, very high accuracy is required for the stop position of the transparent original plate 8. On the other hand, in the present embodiment, as described above, the accuracy of the stop position of the diffractive optical element plate 3 is not so required.

Next, the second advantage will be described. This advantage is also obtained by performing image formation by utilizing the diffraction phenomenon. During the switching from the situation of FIG. 5 to the situation of FIG. 6 described above, as shown in FIG. 9, there is a timing at which the laser light L is emitted across both the first region 4 and the second region 5. To do. At this timing, as shown in FIG. 10, the diffraction image by the first region 4 (constellation picture) and the diffraction image by the second region 5 (mark line group) are displayed in an overlapping manner on the screen 6. The position of the image of the constellation picture on the screen 6 in the situation of FIG. 10 is the same as the position of the image in the situation of FIG. Similarly, the positions of the images of the mark line group are the same in FIGS. 10 and 6. The reason is as described in the above-mentioned “first advantage”.

Therefore, the actual situation of the projected image on the screen 6 at the time of switching the image in this embodiment is as follows. The initial state is the state in which the constellation picture shown in FIG. 5 is projected. When the image switching starts, the image of the group of landmarks appears faintly and is superimposed on the constellation picture of FIG. Then, as the image switching progresses (that is, the diffractive optical element plate 3 moves), the image of the group of landmarks gradually becomes brighter, and the state shown in FIG. 10 is reached. As the switching progresses further, the image of the constellation picture gradually fades. When the image of the constellation picture finally disappears and the state shown in FIG. 6 is reached, the switching is completed. Of course, even in the case of switching from the state of FIG. 6 to the state of FIG. 5, it is the same except that the constellation picture and the group of landmarks are reversed.

In the process of switching the image, neither the constellation picture nor the group of landmarks moves on the screen 6 and remains at the original projection position. The reason is as described above. For this reason, the image on the screen 6 seems to the viewer to gradually transition from one of the constellation picture and the group of landmarks to the other. In other words, this image switching is very natural for the viewer. It is also possible to intentionally stop the movement of the diffractive optical element plate 3 in the state of FIG. 10 and statically perform projection in the superimposed image mode. It is undeniable that the constellation picture and the group of landmarks in the middle of the above image switching are darker than in the one-image mode of FIGS. 5 and 6. This is because the energy of the original laser light L is dispersed in both images. Therefore, the brightness of the image may be maintained by increasing the light amount of the laser light source 2 during the image switching.

The fact that images can be naturally switched in this way is also different from the case of projecting an image using a conventional transparent original plate. As shown in FIG. 11, when image switching is performed by projecting with the diffused light source 7 and the transmission original plate 11, a projected image in which two parts of the two images are arranged halfway appears on the screen 6. The situation of FIG. 11 is in the middle of transition from projection by the portion of the transmission original plate 8 of the transmission original plate 11 to projection by the portion of the transmission original plate 9. When the projected image is switched by the transparent original plate, the previous image exits to one side and the next image enters from the other instead, so the projected situation as shown in FIG. 11 appears. is there. Of course, in the meantime, the previous image and the next image move on the screen 6. The projection state as shown in FIG. 11 looks unnatural to the viewer.

In the case shown in FIG. 11, it is possible to project the superimposed image as shown in FIG. However, it is because the transparent original plate 9 which is an area for projecting the superimposed image itself is prepared in the transparent original plate 11. The image of the transparent original plate 8 and the image of the transparent original plate 10 cannot be projected in an overlapping manner. On the other hand, in the present embodiment, natural image switching is possible as described above. Further, in the diffractive optical element plate 3, it is not necessary to provide a region corresponding to the original transmission plate 9 in FIG.

By utilizing the characteristics of the image projection device 1 of the present embodiment as described above, it is possible to perform an effect as shown in FIG. FIG. 12 shows how the image projected on the screen 6 changes from (a) to (f) in order. In order to perform the effect of FIG. 12, the diffractive optical element plate 12 of FIG. 13 is used. The diffractive optical element plate 12 of FIG. 13 is obtained by adding a third region 13 to the diffractive optical element plate 3 of FIG. As shown in FIG. 13A, the third region 13 is a diffraction grating formed with a CGH pattern that projects only the portion corresponding to the Big Dipper in the Okuma constellation group.

In the presentation of FIG. 12, first, as shown in (a), the third region 13 of the diffractive optical element plate 12 is used to project the group of landmarks of the Big Dipper on the screen 6. The screen 6 when the diffractive optical element plate 12 is moved from this state to a state in which projection by the second area 5 is performed is shown in (b). The projected image at this time is the same as that shown in FIG. Here, in the eyes of the viewer, when the state of (a) changes to the state of (b), the group of landmarks of the Big Dipper is unchanged, and the group of landmarks of the Great Bear constellation is the Big Dipper. The parts corresponding to the other parts seem to gradually emerge.

When the diffractive optical element plate 12 is further moved from the state of (b), the projected image changes as (c), (d), (e) and (f). That is, the constellation picture appears slightly as described above (c). Then, the constellation picture gradually becomes brighter, while the group of landmarks (including the part of the Big Dipper) gradually becomes darker ((d), (e)). The state where the marker line group has completely disappeared is (f), and at this time, in the diffractive optical element plate 12, only the first region 4 is irradiated with the laser light L. This change in brightness between the constellation picture and the group of landmarks in the process of (c)→(e) is due to the fact that the laser beam L is actually irradiated in the second region 5 and the first region 4. It is because the area ratio of is changing.

Here, the configuration of the control system of the image projection apparatus 1 of this embodiment will be described. The control system of the image projection device 1 is configured as shown in FIG. The control system of FIG. 14 includes a control unit 14 and a drive unit 15. The control unit 14 is a unit that controls light emission of the laser light source 2 and movement control of the diffractive optical element plates 3 and 12. The drive unit 15 is a mechanical unit that moves the diffractive optical element plates 3 and 12 under the control of the control unit 14, and is configured by a combination of known motors and gears.

The movement control of the diffractive optical element plates 3 and 12 among the control functions of the control unit 14 in this embodiment means that the diffractive optical element plates 3 and 12 are switched in order to switch the projected images such as the constellation picture and the group of landmarks. It is the control to move. Among them, the one-image mode described above ((a), (b), (f) in FIGS. 5, 6 and 12) and the superimposed image mode ((c) to (e) in FIGS. 10 and 12). )) is included. Further, the light emission control of the laser light source 2 includes the light amount increase control at the time of switching the projected image. Of course, even when the diffractive optical element plates 3 and 12 are stopped in the superimposed image mode, the amount of light can be increased. Further, the increased light amount may be constant from the start to the completion of the image switching, or the light amount may be changed in a mountain shape.

As a modified example of the image projection apparatus 1 of the present embodiment, the one shown in FIG. 15 can be cited. In this modified example, instead of moving the diffractive optical element plate 3, a plurality of emitting portions of a laser light source are used. That is, in the configuration example of FIG. 15, the laser light source 19 having the three emitting portions 16 to 18 is used. The emitting section 16 is an emitting section for projecting in one image mode by the first region 4 of the diffractive optical element plate 3. The emission unit 17 is an emission unit for projecting the superimposed image mode by the first region 4 and the second region 5 of the diffractive optical element plate 3. That is, the emitting portion 17 is arranged at a position where the emitted laser light is applied across both the first region 4 and the second region 5. The emitting portion 18 is an emitting portion for projecting in the one-image mode by the second region 5 of the diffractive optical element plate 3.

The switching control of the projected image in the case of this modified example is performed by switching among the emitting units 16 to 18 that actually emit light. Here, two or more of the emission parts 16 to 18 can be made to emit light at the same time. Further, it is also possible to gradually increase or decrease the amount of light emitted from the emitting portions 16 to 18 individually. As a result, the effects as shown in (b) to (f) of FIG. 12 can be performed. In addition, the emitting unit 17 of the emitting units 16 to 18 is not essential. This is because the superimposition image mode can be realized by causing the emitting units 16 and 18 to emit light at the same time without causing the emitting unit 17 to emit light.

Strictly considering here, if the diffractive optical element plate 3 is exactly the same as that in FIG. 10 in the configuration example of FIG. 15, the position of the constellation picture on the screen 6 and the position of the marker line group may be slightly shifted. Become. However, the amount of deviation is the same as the distance between the emitting portions 16 to 18 in the laser light source 19, and is not expanded. Therefore, the shift amount is not so noticeable by the viewer on the screen 6. This is because, for example, in the case of a planetarium, the projected image is projected at a position separated by about 10 m in a size of about several square meters. On the other hand, the distance between the emitting parts 16 to 18 is usually only about 2 to 4 mm, so that a projected image of several square meters is displaced by about 2 to 4 mm. This is because it can be said that this is only within the error range. The intervals of the emitting portions 16 to 18 are of course adjusted to the sizes of the first region 4 and the second region 5 in the diffractive optical element plate 3. This is because the beam system of the laser light L is usually about 1 to 3 mm.

The image projection apparatus of this embodiment is useful as, for example, the sub projection unit 48 of the planetarium projection apparatus 47 shown in FIG. The planetarium projection device 47 has a normal main projection unit 49 in addition to the sub projection unit 48. The sub projection unit 48 is arranged between the main projection units 49. The main image projected from the main projection unit 49 is mainly a Hoshino image. The sub-image projected from the sub-projection unit 48 is an image whose shape is defined as a diffraction image by the diffractive optical element plates 3 and 12 described above. With such a planetarium projection device 47, the main image and the sub-image can be superimposed and projected on the dome screen. For example, the star image projected from the main projection unit 49 can be superposed with the constellation picture projected from the sub projection unit 48, the group of landmarks, or both of them.

The image projection apparatus of this embodiment is also useful as a sub-image projection apparatus 51 in the planetarium 50 as shown in FIG. In addition to the projection device 51, FIG. 17 shows a main image projection device 52, a dome screen 53, and an operation console 54. The projection device 52 is a normal planetarium projection device that does not have the sub-projection unit 48 described above. Instead, the projection apparatus 51 is provided separately from the projection apparatus 52 in the configuration example of FIG. Even with such a configuration, the main image projected by the projection device 52 and the sub-image projected by the projection device 51 are projected on the dome screen 53 in an overlapping manner.

As described above in detail, according to the present embodiment, the diffractive optical element plates 3 and 12 are arranged on the optical path of the laser light L, and at least the first region 4 and the second diffractive optical element plates 3 and 12 are provided. Area 5 is provided. Then, by moving the diffractive optical element plates 3 and 12 in the in-plane direction, or by properly using the plurality of emitting portions 16 to 18, it is possible to perform projection in the single-image mode or the superimposition mode. I am trying. As a result, not only two or more separate images can be switched and projected, but also individual images can be projected to their original projection positions even during the switching of images. Has been realized.

The present embodiment is merely an example and does not limit the present invention. Therefore, naturally, the present invention can be variously improved and modified without departing from the scope of the invention. For example, when switching the images to be projected, the movement of the diffractive optical element plates 3 and 12 in the in-plane direction and the proper use of the plurality of emission units 16 to 18 may be used together.

Further, the number of CGH regions in the diffractive optical element plates 3 and 12 may be 4 or more. The arrangement of the CGH regions in the diffractive optical element plate having four or more CGH regions may be linear as illustrated in FIG. 18 or may be two-dimensional as illustrated in FIG. In the case of the two-dimensional arrangement as shown in FIG. 19, a maximum of four types of diffraction images can be superimposed and projected simultaneously. Further, a gap portion 20 may exist between each CGH region, as illustrated in FIG. However, the gap portion 20 is preferably made of a material that is opaque to the laser light L. Further, it is desirable that the width of the gap portion 20 is one third or less of the beam diameter of the laser light L so that it does not hinder the projection in the superimposed image mode. When the gap portion 20 is provided in the two-dimensional arrangement of FIG. 19, the length of the diagonal line at the intersection of the gap portion 20 is preferably one third or less of the beam diameter of the laser light L.

1 Image Projection Device 2, 19 Laser Light Source 3, 12 Diffractive Optical Element Plate 4 First Region 5 Second Region 6, 53 Screen 13 Third Region 14 Control Unit 16-18 Emission Unit 47 Planetarium Projection Device 48 Sub Projection Unit 50 Planetarium 51 Projector

Claims (11)

The diffractive image includes: a laser oscillating unit that outputs a laser beam; An image projecting device for projecting an image on a screen,
The diffractive optical element is provided with a first diffraction grating region for generating a first diffraction image and a second diffraction grating region for generating a second diffraction image,
A projection mode switching unit that switches modes for projection of a diffraction image by the diffractive optical element;
The projection mode that can be switched by the projection mode switching unit,
A one-image mode in which a diffraction image is projected using only one of the first diffraction grating region and the second diffraction grating region;
And a superimposition mode for projecting a diffraction image using both the first diffraction grating region and the second diffraction grating region ,
The laser oscillation unit, when projection mode by the projector mode switching unit is in the superimposed image mode, the image projection apparatus according to claim der Rukoto that increasing the amount of light than when the a first image mode. The image projection apparatus according to claim 1, wherein the projection mode switching unit includes:
An image projection apparatus, wherein mode switching is performed by moving the diffractive optical element in an in-plane direction intersecting an optical path of a laser beam output from the laser oscillator. The image projection apparatus according to claim 2, wherein
During the transition from the first one-image mode using the first diffraction grating area to the second one-image mode using the second diffraction grating area by the movement of the diffractive optical element, the laser light is An image projection apparatus, wherein the image is projected in the superimposed image mode by being irradiated over both the first diffraction grating region and the second diffraction grating region. The image projection apparatus according to claim 1, wherein
The laser oscillation unit has a plurality of emission units for emitting laser light,
The image projection apparatus, wherein the projection mode switching unit switches modes by switching which of the plurality of emitting units is used. The image projection device according to claim 4,
Some of the plurality of emitting portions are arranged such that the emitted laser light is radiated across both the first diffraction grating region and the second diffraction grating region,
In the superimposed image mode, the image projection apparatus is characterized in that a diffraction image is projected by one of the plurality of emitting portions arranged at the position. A laser oscillator that outputs laser light,
An image projection device provided on the optical path of the laser light output from the laser oscillator and having a diffractive optical element that generates a diffracted image based on the diffraction of the laser light ,
With a dome screen,
A planetarium for projecting the diffraction image on the dome screen by the image projecting device,
The diffractive optical element is provided with a first diffraction grating region for generating a first diffraction image and a second diffraction grating region for generating a second diffraction image,
A projection mode switching unit that switches modes for projection of a diffraction image by the diffractive optical element;
The projection mode that can be switched by the projection mode switching unit,
A one-image mode in which a diffraction image is projected using only one of the first diffraction grating region and the second diffraction grating region;
Planetarium, wherein Rukoto includes a superimposed image mode for projector to project a diffraction image using both of the first diffraction grating region and the second diffraction grating region. The planetarium according to claim 6 , wherein the projection mode switching unit includes:
A planetarium for performing mode switching by moving the diffractive optical element in an in-plane direction intersecting an optical path of a laser beam output from the laser oscillator. The planetarium according to claim 7 ,
During the transition from the first one-image mode using the first diffraction grating area to the second one-image mode using the second diffraction grating area by the movement of the diffractive optical element, the laser light is A planetarium characterized in that it is projected over both the first diffraction grating region and the second diffraction grating region to project the superimposed image mode. The planetarium according to claim 6 ,
The laser oscillation unit has a plurality of emission units for emitting laser light,
The planetarium, wherein the projection mode switching unit switches modes by switching which of the plurality of emitting units is used. The planetarium according to claim 9 ,
Some of the plurality of emitting portions are arranged such that the emitted laser light is radiated across both the first diffraction grating region and the second diffraction grating region,
A planetarium characterized in that, in the superposed image mode, a diffracted image is projected by one of the plurality of emitting portions arranged at the position. The planetarium according to any one of claims 6 to 10 , wherein the laser oscillation unit comprises:
A planetarium characterized in that when the projection mode by the projection mode switching unit is the superimposition image mode, the amount of light is larger than in the single image mode.

Images