WO2023277080A1

WO2023277080A1 - Aerial projection device

Info

Publication number: WO2023277080A1
Application number: PCT/JP2022/026020
Authority: WO
Inventors: 直樹 ▲高▼田; 好洸小田; 康平鈴木; 嘉軌森口; 隆史山崎; 永久三谷; 十内内田
Original assignee: 国立大学法人高知大学
Priority date: 2021-06-29
Filing date: 2022-06-29
Publication date: 2023-01-05
Also published as: JPWO2023277080A1

Abstract

Provided is an aerial projection device that can display an image in midair by using an image display means having a simple structure. This aerial projection device 10 is configured from: a holographic projector unit 10a that emits diffracted light which is illuminated collimated light diffracted on the basis of interference information regarding a hologram of a cube which is a prescribed image; and a projection unit 10b that comprises a stereoscopic screen 28 onto which the diffracted light is illuminated such that the cube is projected thereon, a second half-silvered mirror 30 which is disposed at an angle relative to the diffracted light illuminated onto the stereoscopic screen 28 at a location illuminated by transmitted-diffused light of the diffracted light that has been transmitted through and diffused by the screen, and a retroreflective sheet 32 which is illuminated by light transmitted through the second half-silvered mirror 30, wherein a real image 34 of the cube is formed in midair by reflected light, which is obtained by the light transmitted through the second half-silvered mirror 30, of the transmitted-diffused light, being reflected by the retroreflective sheet 32, emitted in the opposite direction along the original incidence path, and reflected by the second half-silvered mirror 30.

Description

aerial projection device

The present invention relates to an aerial projection device.

Aerial projectors that can image button images in the air, or image predetermined images in the air for education, games, etc., in order to make the buttons of elevators and the like non-contact type for the prevention of infection of infectious diseases. What is desired is an aerial projection system that can As such an aerial projection device, for example, Patent Document 1 below describes an aerial image forming device capable of projecting an image displayed on a display device in the air. In this aerial image forming apparatus, light output from a display device is reflected by a beam splitter toward a retroreflective sheet, and the light retroreflected by the retroreflective sheet passes through the beam splitter and travels in the air. It forms an image. In addition, Japanese Unexamined Patent Application Publication No. 2002-200002 also describes a spatial display device capable of forming an image displayed on an image display unit in the air. In this spatial display device, the light output from the image display unit is reflected by the selective reflection film toward the retroreflection material, retroreflected by the retroreflection material, transmitted through the selective reflection film, and condensed in the air. It is an image.

JP 2019-207574 A Japanese Patent Application Laid-Open No. 2018-92000

According to the aerial image forming apparatus and the spatial display apparatus described in

Patent Documents

1 and 2, images displayed on the display device or the image display unit can be displayed in the air. However, as described in Patent Document 2, the display device and the image display unit are required to emit image light having three-dimensional positional information, and the structure thereof becomes complicated. For example, the image display unit disclosed in Patent Document 2 has a microlens array arranged on the display surface of a display panel such as a liquid crystal display panel. An aerial image forming apparatus or spatial display apparatus using such an image display means having a complicated structure is complicated as a whole.

The present invention has been made to solve the above problems, and an object of the present invention is to provide an aerial projection device capable of displaying an image in the air using an image display means with a simple structure.

An aerial projection apparatus according to the present invention, which has been made to achieve the above object, comprises a holographic projector section for emitting diffracted light obtained by diffracting irradiated parallel light based on interference information of a hologram of a predetermined image; a screen onto which the predetermined image is projected by irradiating the diffracted light; and a projection unit composed of a retroreflective element that is irradiated with the transmitted light or reflected light of the half mirror, and the transmitted diffused light of the half mirror Alternatively, the reflected light is retroreflected by the retroreflective element and emitted in the opposite direction along the original incident path, and the reflected light reflected by the half mirror or the transmitted light transmitted through the half mirror forms the predetermined image. is formed in the air on one side of the half mirror.

By arranging the screen at a position in front of or behind a predetermined position where the screen is projected based on the interference information of the hologram so that the real image appears blurred, the range of expression of the aerial projection device can be widened. can.

The retroreflective element is tilted so that a virtual image corresponding to the real image viewed on the other side of the half mirror moves out of the field of view due to specular reflection of the retroreflective element, so that the real image is Clearly visible.

The holographic projector unit emits diffracted light diffracted based on the interference information of each hologram of at least two predetermined images, and the screen is irradiated with the diffracted light based on the interference information of one of the predetermined images. The screen is irradiated with diffracted light based on the interference information of the other of the predetermined images along with one of the predetermined images formed in the air via the half mirror and the retroreflective element. without passing through the half mirror and illuminating the retroreflected light exit surface of the retroreflective element, the other of the predetermined images is projected, and the retroreflected light emitted from the retroreflected light exit surface is projected. Due to the light reflected by the half mirror, the other virtual image of the predetermined image can be visually recognized in the air on the side opposite to the reflecting surface of the half mirror, so that the real image and the virtual image can be recognized at the same time.

The screen and/or the retroreflective element are arranged at a position forward or rearward of a predetermined position projected based on the interference information of the hologram so that the real image and/or the virtual image appear blurred. As a result, one or both of the real image and the virtual image can be made to appear blurred, and the expression range of the aerial projection device can be further expanded.

A stereoscopic image can be formed in the air because the screen is a stereoscopic screen.

　Since the screen is made of Japanese paper or non-woven fabric, a screen such as a three-dimensional screen can be easily formed.

At least two pairs of the half mirror and the screen are provided, and the two pairs are arranged in series with a predetermined interval so that the real image is formed in the air on the same side of each of the half mirrors. By being installed, a complex real image can be formed in the air.

The projection image corresponding to one of the real images is projected by the holographic projector such that at least one of the real images formed in the air on the same surface side of each of the half mirrors moves in a direction toward or away from the half mirror. Since the screen projected from the unit is movable in the direction of contact and separation with respect to the half mirror, by moving the screen in the direction of contact and separation with respect to the half mirror, the real images It is possible to add motion such that one of the real images is superimposed on the other, or behind the other real image.

The hologram is a computer-generated hologram, and a spatial light modulator is provided for modulating the parallel light into diffracted light based on the interference information of the computer-generated hologram, so that a desired hologram can be easily created. preferable.

The computer-generated hologram is an amplitude hologram, and the amplitude hologram is represented by the following formula (1)

can speed up the calculation of the amplitude hologram.

The computer-generated hologram is a phase hologram, and the phase hologram is represented by the following formula (2)

can increase the calculation speed of the phase hologram.

The aerial projection apparatus according to the present invention irradiates the image display means with a hologram in which interference information of a predetermined image is recorded and diffracted light diffracted based on the interference information of this hologram. A simple structure consisting of a screen having both lightness and diffusing properties can be achieved, and the structure of the entire device can also be simplified.

1 is a schematic diagram illustrating an aerial projection device to which the present invention is applied; FIG. FIG. 11 is a schematic diagram illustrating another aerial projection device to which the present invention is applied; FIG. 11 is a schematic diagram illustrating another aerial projection device to which the present invention is applied; FIG. 10 is an explanatory diagram illustrating the state of a real image when the position of the screen is moved, in another aerial projection device to which the present invention is applied; FIG. 11 is another aerial projection device to which the invention is applied, and is an explanatory diagram for explaining movement of a virtual image visually recognized corresponding to a real image when the retroreflective element is tilted. FIG. 10 is a schematic diagram illustrating another aerial projection device to which the present invention is applied, which allows a real image and a virtual image to be visually recognized at the same time. FIG. 10 is a schematic diagram illustrating the states of the real image and the virtual image when the retroreflective sheet is moved, in the aerial projection device to which the present invention is applied and in which a real image and a virtual image can be visually recognized at the same time. FIG. 10 is a schematic diagram illustrating a state in which a retroreflective sheet is divided and arranged when a planar screen is used, in an aerial projection device to which the present invention is applied and in which a real image and a virtual image can be viewed simultaneously; FIG. 10 is a schematic diagram illustrating a state in which a retroreflective sheet is divided and arranged in an aerial projection apparatus that allows viewing of a real image and a virtual image at the same time using a stereoscopic screen to which the present invention is applied; FIG. 2 is a schematic diagram illustrating a measuring device for measuring visible light transmittance and diffusivity of a material used for a screen; FIG. 4 is a schematic diagram illustrating an aerial projection device that allows a plurality of virtual images to be visually recognized in the air at the same time; FIG. 12 is a perspective view illustrating an installation state of a retroreflective sheet used in the aerial projection device shown in FIG. 11; 12A and 12B are schematic diagrams for explaining how a virtual image appears when a light shielding object is placed on the other surface side of the second half mirror that constitutes the aerial projection device shown in FIG. 11; FIG. 12 is a schematic diagram illustrating movement of a virtual image when one of the two retroreflective sheets used in the aerial projection device shown in FIG. 11 is vertically moved; 12A and 12B are schematic diagrams for explaining movement of a virtual image when an optical path from one half mirror 30 of two retroreflective sheets used in the aerial projection apparatus shown in FIG. 11 is lengthened. 12A and 12B are schematic diagrams for explaining the movement of a virtual image when one retroreflective sheet is used in the aerial projection device shown in FIG. 11 and the retroreflective sheet is made movable; FIG. 12 is a schematic diagram illustrating how a virtual image appears when two retroreflective sheets used in the aerial projection device shown in FIG. 11 are arranged side by side in the horizontal direction of a rectangular half mirror; FIG. 18(a) is a schematic diagram for explaining a guide device for guiding the stereoscopic screen to the projection position of the holographic projector section of the aerial projection device. FIG. 18(b) is a perspective view showing a projection state when the stereoscopic screen is positioned at the projection position of the holographic projector unit, and FIG. FIG. 10 is a perspective view showing a projection state in this case; FIG. 19(a) is a front view showing the projection state when the planar screen is positioned at the projection position of the holographic projector unit, and FIG. FIG. 10 is a front view showing a projection state when the object is out of the (focus position); FIG. 19 is a schematic diagram illustrating an example in which the guide device shown in FIG. 18 is used as a personal authentication device; FIG. 19 is a schematic diagram illustrating an example in which the guide device shown in FIG. 18 is used in another personal authentication device; It is a conceptual diagram for explaining the principle of creating a computer-generated hologram. FIG. 4 is a schematic diagram illustrating the configuration of a CGH calculator that calculates an amplitude hologram; Pseudocode to compute the amplitude hologram. Fig. 4 is a flow chart for computing amplitude holograms; FIG. 4 is a schematic diagram illustrating the configuration of a CGH calculator that calculates a phase hologram; Pseudocode to compute the phase hologram. Fig. 4 is a flow chart for computing a phase hologram; FIG. 29(a) is another pseudocode to compute the amplitude hologram, and FIG. 29(b) is another pseudocode to compute the phase hologram. 4 is a schematic diagram illustrating a case where three projection units 10b of the aerial projection device shown in FIG. 3 are arranged; FIG. FIG. 31 is a schematic diagram illustrating the moving direction of the real image when the frame 26 of the projection unit 10b-2 of the two projection units 10b-1 and 10b-2 shown in FIG. 30 is vertically moved;

Although the present invention will be described in detail below, the scope of the present invention is not limited to these.

An aerial projection device to which the present invention is applied is shown in FIG. 1(a). The aerial projection device 10 shown in FIG. 1(a) comprises a holographic projector section 10a and a projection section 10b. The holographic projector section 10a is composed of a personal computer (PC) 12 to which a tablet terminal device 11 is connected, a reflective spatial light modulator (SLM) 14, a first half mirror 22, and a parallel light emitting section 15. . The parallel light emitting section 15 is composed of a laser light emitting section 16 , an objective lens 18 and a plano-convex lens 20 . In the holographic projector unit 10 a , a cubic computer-generated hologram (CGH) as a predetermined image input from the tablet terminal device 11 is calculated by the CGH calculation unit 17 of the PC 12 and displayed on the SLM 14 . The interference fringes displayed on the SLM 14 are interference information hologrammed such that a cube is projected at a given location. Parallel light is applied to the display surface of the SLM 14 on which such interference fringes are displayed. This parallel light is emitted from the laser light emitting portion 16 of the parallel light emitting portion 15. After being condensed once by the objective lens 18, the parallel light spreads, becomes parallel light by the plano-convex lens 20, and reaches the SLM 14 by the first half mirror 22. It is the light reflected in the direction of the display surface. The parallel light irradiated to the display surface of the SLM 14 becomes diffracted light based on the hologram interference information displayed on the display surface, emerges from the display surface of the SLM 14 , and is emitted from the first half mirror 22 . and is emitted to the projection unit 10b.

The projection unit 10b includes a mirror 24, a horizontally placed frame 26, a three-dimensional screen 28 supported by a support base 27 placed on the frame portion of the frame 26, and inclined at 45° with respect to the frame 26. It is composed of a second half mirror 30 having an inclination angle of 45° and a retroreflective sheet 32 as a retroreflective element arranged so as to face the frame 26 . The diffracted light incident on the projection unit 10b from the holographic projector unit 10a is reflected by the mirror 24 placed at an inclination angle of 45°, passes through the hollow part of the frame 26, and irradiates the three-dimensional screen 28. FIG. The three-dimensional screen 28 is formed in a shape similar to a cube as a predetermined image for which the computer-generated hologram is calculated, and is supported by a support base 27 at a predetermined position which is the premise of the calculation of the computer-generated hologram.

As shown in FIG. 1B, the three-dimensional screen 28 is formed by pasting a Japanese paper 28c (texture pasting paper: basis weight 18 g/m ² ) to a frame 28b. The Japanese paper 28c has a transmittance of 55% or more on the optical axis of the irradiated visible light (a green laser beam with a wavelength of 532 nm). 30, the diffusion rate of -10° to +10° with respect to the optical axis of the visible light (green laser light with a wavelength of 532 nm) of the visible light transmitted through the Japanese paper 28c among the irradiated visible light. 15% or more. The Japanese paper 28c forms three faces of a cube, and is supported by the support base 27 so that the three faces to which the Japanese paper 28c is pasted face the frame 26 as shown in FIG. 1(a). When such a stereoscopic screen 28 is irradiated with diffracted light, a projection image 28a of a hologramized cube is projected. The Japanese paper 28c forming the three surfaces of the three-dimensional screen 28 is a transmissive diffuser through which at least part of the irradiated diffracted light is transmitted and diffused. The light transmitted through each of the

projection points

29a, 29a is diffused to become transmitted diffused light. This transmitted diffused light is transmitted through the second half mirror 30 and is incident on the retroreflective sheet 32 .

As shown in FIG. 1(c), the retroreflective sheet 32 has a large number of glass beads 33b arranged in a transparent resin layer 33c formed on one side of a reflective sheet 33a. retroreflection in which the outgoing light is emitted in the direction opposite to the incident light along the incident path of the incident light. The diffused light incident on the retroreflective sheet 32 is emitted in the opposite direction along the incident path of the incident light as shown in FIG. A three-dimensional cubic real image 34 is formed in the air on one side of the half mirror 30 .

Projection points

29a and 29b of a cubic projection image 28a projected onto the stereoscopic screen 28 correspond to

imaging points

34a and 34b of the real image 34, respectively. The real image 34 shown in FIG. 1(a) has a shape viewed from the side, and an enlarged view thereof viewed from the front is shown in FIG. 1(d).

Points

34a and 34b shown in FIG. 1(d) correspond to

imaging points

34a and 34b of the real image 34 shown in FIG. 1(a). The real image 34 shown in FIG. 1 was a cube, but when changing the shape to another shape, the other shape is input from the tablet terminal device 11 to the PC 12, and the computer-generated hologram of the other shape is calculated by the PC 12. , the SLM 14 can easily display interference fringes of other shapes. The same applies when adding a pattern to the shape. Although the retroreflection sheet 32 shown in FIG. 1(c) uses a large number of glass beads 33b, it may be a retroreflection sheet using a large number of prisms.

The projection unit 10b of the aerial projection apparatus 10 shown in FIG. 1 is arranged parallel to the frame 26 in which the retroreflective sheet 32 is arranged horizontally. It may also be arranged perpendicular to the body 26 . Also in this case, the real image 34 is formed at substantially the same aerial position as the projection unit 10b shown in FIG. However, in this case, when the real image 34 is viewed from the front, the image reflected by the retroreflective sheet 32 may enter the field of vision.

1 and 2, the three-dimensional screen 28 was used, but as shown in FIG. 3, a flat screen 36 (hereinafter simply referred to as screen 36). A projection image 36a projected onto such a single screen 36 is a two-dimensional image (triangle) as shown in FIG. 3(b), and a real image 38 formed in the air is also a two-dimensional image. . FIG. 3(c) shows the shape of the real image 38 (triangle) formed in the air as viewed from the front. FIG. 3(c) shows

imaging points

38a and 38b of the real image 38 corresponding to the projection points 37a and 37b of the projection image 36a shown in FIGS. 3(a) and 3(b).

In the aerial projection device 10 shown in FIGS. 1 to 3, the interference fringes displayed on the SLM 14 of the holographic projector section 10a are arranged such that a predetermined image is clearly projected on the installed stereoscopic screen 28 or screen 36, in other words, It is a computer-generated hologram (CGH) calculated by the CGH calculator 17 of the PC 12 so that the 3D screen 28 or the screen 36 is in focus. Here, without changing the focal position of the CGH, the frame 26 on which the screen 36 of FIG. That is, when the focal position of the CGH is moved backward, the projection image 36a' (two-dimensional image (triangle)) projected on the screen 36 becomes blurred as shown in FIG. ' also has a blurred shape as shown in FIG. 4(c). Moreover, this real image 38' is formed at a position closer to the second half mirror 30 as shown in FIG. 4(a). In this manner, the aerial image can be made into a blurred shape simply by moving the position of the screen 36, and the range of representation of the aerial image can be expanded. For example, by gradually moving the screen 36 away from the second half mirror 30 side, the aerial image can be changed from a blurred shape located far away to a clear shape located close, and an object moving from far to near can be represented. It becomes possible. In FIG. 4, the position of the screen 36 is moved behind the focal position of the CGH, but even if it is moved forward (toward the mirror 24) of the focal position of the CGH, the real image 38' becomes blurred. However, in this case, the space between the real image 38 ′ and the second half mirror 30 is wider than the space between the real image 38 and the second half mirror 30 . Although FIG. 4 shows an example of the screen 36, the stereoscopic screen 28 can be moved in the same way.

In the retroreflection sheet 32 shown in FIGS. 1 to 4, part of the irradiated diffracted light is mirror-reflected to form a real image 38 on the other side of the second half mirror 30 as shown in FIG. A corresponding virtual image 39 is visible. This virtual image 39 poses no problem if the real image 38 is clear, but if the real image 38 becomes somewhat unclear, the virtual image 39 may become an eyesore. In such a case, by inclining the retroreflective sheet 32 as shown in FIG. can. The retroreflective sheet 32 indicated by the solid line in FIG. 5(b) is tilted so that the real image 38 side (the front side from the viewer) is lowered, in which case the virtual image 39' moves downward. On the other hand, the retroreflective sheet 32' indicated by the dashed line in FIG. 5B is tilted so that the real image 38 side is higher, in which case the virtual image 39'' moves upward. In FIG. Although the retroreflection sheet 32 is tilted forward and backward, the virtual image 39 can be moved leftward and rightward and out of the field of vision even when the retroreflective sheet 32 is tilted leftward and rightward.

1 to 5 have explained the aerial projection device that forms a real image in the air. can be simultaneously displayed on the SLM 14, the diffracted light diffracted based on the interference information of each hologram of at least two predetermined images can be simultaneously emitted from the holographic projector section 10a. Therefore, as shown in FIG. 6A, part of the diffracted light based on the interference information of one of the predetermined images is irradiated onto the screen 36 placed on the frame 26 to project the projected image 36a. One of the real images 38 of the predetermined image formed in the air by the transmitted diffused light transmitted through the screen 36 and diffused via the second half mirror 30 and the retroreflective sheet 32 as a retroreflective element can be visually recognized. At the same time, without irradiating the screen 36 with the diffracted light based on the interference information of the other of the predetermined image, it passes through the second half mirror 30 and irradiates the retroreflected light exit surface of the retroreflective sheet 32 to irradiate the other of the predetermined image. , and the retroreflected light from each of the projection points 40a and 40b of the projected image 40 of the retroreflected light exit surface is reflected by the second half mirror 30, and is reflected by the second half mirror The other virtual image 42 of the predetermined image can be visually recognized in the air on the side opposite to the reflecting surface of 30 .

Points

42 a and 42 b shown in FIG. 6 correspond to the projection points 40 a and 40 b of the projection image 40 . As described above, according to the aerial projection device 10 shown in FIG. 6(a), the real image 38 and the virtual image 42 can be viewed simultaneously as shown in FIG. 6(b). In the aerial projection apparatus 10 shown in FIG. 6, the focal position of one CGH of the predetermined image is the screen 36 and the focal position of the other CGH of the predetermined image is the retroreflective sheet 32 .

In the aerial projection apparatus 10 shown in FIG. 6 as well, the virtual image 42 can be displayed in a clear state by moving only the screen 36 to the front or rear of the CGH focal position as shown in FIG. 4 without changing the CGH focal position. , so that only the real image 38 has a blurred shape. Further, as shown in FIG. 7(a), by moving the retroreflective sheet 32 to a position 32' behind the focal position of the CGH, the projection image 40' projected onto the retroreflective sheet 32 is blurred. A virtual image 42' having a blurred shape can be obtained as shown in FIG. 7(b). Since the gap between the retroreflective sheet 32 moved to the position 32' and the second half mirror 30 widens, the virtual image 42' is separated from the second half mirror 30 as shown in FIG. position. Since the position of the screen 36 does not change, the real image 38 is formed at the same position while maintaining a clear state. Points 42a' and 42b' shown in FIG. 7(a) correspond to the projected points 40a' and 40b' of the retroreflective sheet 32 moved to the position 32'.

As shown in FIG. 8, by dividing the retroreflective sheet 32a for the real image and the retroreflective sheet 32b for the virtual image, only the retroreflective sheet 32b is moved, and only the virtual image 42 is blurred and the position is also changed. can move. If only the real image 38 is desired to be blurred, this can be achieved by moving the position of the screen 36 . FIG. 8 shows an example of the screen 36, but even when the stereoscopic screen 28 is used, it can be divided into a retroreflective sheet 32a for real images and a retroreflective sheet 32b for virtual images as shown in FIG. Similarly, only the retroreflective sheet 32b can be moved, only the virtual image 42 can be blurred, and the position can also be moved.

In the above description, the stereoscopic screen 28 or the screen 36, or the retroreflective sheet 32 is moved without changing the focal position of the CGH, and the real image 34 (stereoscopic screen 28) or the real image 38 (screen 36) and/or the virtual image is displayed. 42 is blurred and its position is also moved, but by changing the focus position of the CGH, the real image 38 and/or the virtual image 42 can be obtained without moving the screen 36 or the stereoscopic screen 28 or the retroreflective sheet 32. It can be made into a blurred shape without changing the position of . Since the CGH is calculated by the CGH calculator 17 of the PC 12, it is possible to quickly change the focus position of the CGH.

The Japanese paper 28c used in the three-dimensional screen 28 or the screen 36 of the aerial projection device 10 shown in FIGS. , and as shown in FIG. 1, at the height between the highest point of the stereoscopic screen 28 and the middle point of the second half mirror 30, the light diffuses over the entire range of -10° to +10° with respect to the optical axis of visible light. A rate of 15% or more. The measurement of such visible light transmittance was performed using the measuring apparatus shown in FIG. The measurement apparatus shown in FIG. 10 includes a light source 50 that emits visible light such as laser light, an objective lens 52, a plano-convex lens 54, a plate-like body 56 having a hole 58 with a predetermined diameter in the center, and a light meter (laser power meter). ) and a light-receiving surface 62 . The plate-like body 56 is erected at a distance L from the light source 50 so that the center line of the hole 58 coincides with the optical axis 51 of the laser beam from the light source 50 . The light-receiving surface 62 of the light meter is arranged so that the hole 58 and the light-receiving surface 62 of the light meter face each other at a position where the distance M from the plate-like body 56 is equal to the height from the screen to the middle point of the second half mirror 30. is provided in If the screen is a stereoscopic screen 28 as shown in FIG. 1, this distance M is the height between the top end of the stereoscopic screen 28 and the midpoint of the second half mirror 30 (the height indicated by M in FIG. 1). . Further, the light receiving surface 62 of the light meter is provided so as to be rotatable about the center line of the hole 58 as shown in FIG. The radius of rotation of the light receiving surface 62 is the distance M. In the measuring apparatus shown in FIG. 10, the light emitted from the light source 50 is once condensed by the objective lens 52, spreads, becomes parallel light by the plano-convex lens 54, and irradiates the hole 58 of the plate-like body 56. The amount of transmitted light is received by the light-receiving surface 62 of the photometer and measured. This measurement was first performed by bringing the light-receiving surface 62 of the photometer into contact with the plate-like body 56 so as to close the hole 58 (M=0 cm in FIG. 10). The amount of light transmitted at this time is assumed to be _T0 . Then, the measured object 60 is attached so as to close the hole 58, and the light receiving surface 62 is measured by a light meter installed at a position (M = 0 cm) facing the hole 58. Let the quantity be T. Let (T/T ₀ )×100 be the transmittance.
Furthermore, the distance between the light receiving surface 62 of the light meter and the screen material attached to the hole 58 is always kept at 15 cm (rotational radius of the light receiving surface 62: 15 cm), and the light receiving surface 62 of the light meter is aligned with the optical axis 51. The amount of received light is measured at a position 62' after rotating by a predetermined angle ±[theta]. This amount of received light is the amount of diffusion (T') transmitted through the measurement object 60 and diffused in the ±θ directions. The diffusivity is the ratio (T'/T ₁ )×100 to the amount of light received (T ₁ ) measured at the position of 0°.

From the results of measurement with the measurement apparatus shown in FIG. 10, it was found that a screen having a transmittance of at least 47% on the optical axis of the irradiated visible light clearly formed a real image in the air even in a bright room. Visible and particularly preferred. A screen with a transmittance of less than 47% tends to make it extremely difficult to visually recognize a real image formed in the air in a bright room or the like, but the real image can be visually recognized in a dark room or the like. Materials for screens with a visible light transmittance of 47% or more include woven fabrics, nonwoven fabrics, Japanese paper, acrylic diffusion plates made of resin (FANTAREX DREAM D-710M, FANTAREX DREAM D-709M manufactured by Nitto Jushi Kogyo Co., Ltd. Both are trade names), and DF-LFV3-100 (trade name) manufactured by CCS Co., Ltd.). This transmittance is preferably between 55 and 65%. A screen with a transmittance of more than 65%, such as a transparent screen made of a transparent film, forms a real image in the air, but a virtual image due to retroreflection of the retroreflective material is simultaneously visible, making it difficult to see the real image. There is However, by tilting the retroreflective element as described above, it is possible to move the virtual image in the left-right direction or the front-rear direction so that only the real image enters the field of view and is out of the field of view. Also, in order to block excess diffracted light that passes through the second half mirror 30 and irradiates the retroreflective sheet 32 without being irradiated onto the screen, the peripheral portion of the mirror 24 is covered with a light blocking mask to prevent the virtual image. Sometimes it can be erased.

At the height M from the highest point of the stereoscopic screen 28 to the middle point of the second half mirror 30 shown in FIG. is preferably at least 15%. A screen having such a diffusion rate can form a clear real image in the air even in a bright room. In the range of -10° to +10°, a screen with a diffusion rate of less than 15% in some ranges, especially -10° and/or +10°, makes it difficult to see the real image formed in the air in a bright room. There is a tendency. In the case of a screen with a diffusion rate of 78% or more in the range of -10° to +10°, even if the transmittance is 65% or more, a real image formed in the air can be visually recognized.
Based on these measurement results, Japanese paper or non ^- woven fabric is preferable for the screens shown in FIGS. Specifically, thin paper (machine-made Japanese paper: basis weight: 15 g/m ² ), Hidaka Co., Ltd. Tengu sticker (weight basis: 18 g/m ² ), Usumi no 3 momme (weight basis: 20.42 g/m ² ). be able to.

In the aerial projection device described above, a real image is formed in the air, but as shown in FIG. 11, only a virtual image may be visually recognized in the air. The aerial projection device shown in FIG. 11 irradiates parallel light onto a hologram which is created so that each of a plurality of predetermined images is projected at different predetermined positions, and diffracted light diffracted based on the interference information of this hologram is converted into A holographic projector unit 10a to be emitted, a second half mirror 30 installed at an angle with respect to the irradiated diffracted light and through which the diffracted light is irradiated and transmitted, and a predetermined distance from one side of the second half mirror 30 A plurality of sheets arranged without overlapping each other, which are separated from each other and are arranged at predetermined positions where the diffracted light transmitted through the second half mirror 30 is irradiated and projection images corresponding to each of the predetermined images are projected.

retroreflective sheets

32a and 32b as retroreflective elements, and the

retroreflective sheets

32a and 32b are configured to project the retroreflectivity of the projected image emitted from the retroreflective light exit surface. The retroreflected light exit surface is set facing one side of the half mirror 30 so that the reflected light is reflected by the second half mirror 30 and can be visually recognized as a virtual image in the air on the other side of the second half mirror 30, At least one retroreflective sheet among the

retroreflective sheets

32a and 32b is movably provided at the projection position of the corresponding predetermined image, or all of the

retroreflective sheets

32a and 32b or movably provided. Each of the remaining retroreflective sheets other than the retroreflective sheet is arranged at the projection position of the corresponding predetermined image.

The holographic projector section 10a shown in FIG. 11 includes a personal computer (PC) 12 to which a tablet terminal device 11 is connected, a reflective spatial light modulator (SLM) 14, a first half mirror 22, and a parallel light emitting section 15. consists of The parallel light emitting section 15 is composed of a laser light emitting section 16 , an objective lens 18 and a plano-convex lens 20 . In the holographic projector unit 10 a , a computer-generated hologram (CGH) of a predetermined image such as characters and figures input from the tablet terminal device 11 is calculated by the CGH calculation unit 17 of the PC 12 and displayed on the SLM 14 . The interference fringes displayed on the SLM 14 are interference information created so that a given image is formed at a given position. Parallel light is applied to the display surface of the SLM 14 on which such interference fringes are displayed. This parallel light is emitted from the laser light emitting portion 16 of the parallel light emitting portion 15. After being condensed once by the objective lens 18, the parallel light spreads, becomes parallel light by the plano-convex lens 20, and reaches the SLM 14 by the first half mirror 22. It is the light reflected in the direction of the display surface. The parallel light irradiated to the display surface of the SLM 14 becomes diffracted light based on the interference information of the hologram displayed on the display surface, emerges from the display surface of the SLM 14, and passes through the first half mirror 22. Then, the light is emitted to the projection unit 10b.

The projection unit 10b includes a mirror 24 arranged at an inclination angle of 45°, a second half mirror 30 arranged at an inclination angle of 45°, and one surface side (inclined surface side) of the second half mirror 30. It is composed of

retroreflection sheets

32a and 32b as disposed retroreflection elements. The retroreflective sheet 32 a is arranged on the lower end side of the inclined surface of the second half mirror 30 , and the retroreflective sheet 32 b is arranged on the upper end side of the inclined surface of the second half mirror 30 . The

retroreflection sheets

32a and 32b, which are arranged without overlapping each other, have their retroreflected light exit surfaces facing one side of the second half mirror 30, and the CGH is calculated by the CGH calculator 17 of the PC 12. It is also the projection plane of the predetermined image. The diffracted light incident on the projection unit 10b from the holographic projector unit 10a is reflected by the mirror 24, passes through the second half mirror 30, and irradiates the retroreflected light exit surfaces of the

retroreflective sheets

32a and 32b. . A projected image a is projected onto the retroreflective light exit surface of the retroreflective sheet 32a irradiated with the diffracted light. From the retroreflected light exit surface of the retroreflective sheet 32a on which the projected image a is projected, the retroreflected light is emitted in the direction opposite to the incident light of the projected image a. This retroreflected light is reflected by one side of the second half mirror 30 and enters the human eye, and a virtual image a corresponding to the projected image a can be seen in the air on the other side of the second half mirror 30 . The depth from the other side of the second half mirror 30 to the virtual image a (indicated by Fa' in FIG. 11) is the height from the one side of the second half mirror 30 to the retroreflective sheet 32a (indicated by Fa in FIG. 11). shown). A projection image b is projected onto the retroreflection light exit surface of the retroreflection sheet 32b irradiated with the diffracted light. From the retroreflected light exit surface of the retroreflective sheet 32b on which the projected image b is projected, the retroreflected light is emitted in the direction opposite to the incident light of the projected image b. This retroreflected light is reflected by one surface side of the second half mirror 30 and enters the human eye, and a virtual image b corresponding to the projected image b is formed on the other surface side of the second half mirror 30 behind the virtual image a. can be visually recognized. The depth from the other side of the second half mirror 30 to the virtual image b (indicated by Fb' in FIG. 11) is also the height from the one side of the second half mirror 30 to the retroreflective sheet 32b (indicated by Fb in FIG. 11). shown). In this way, when viewed from one side of the second half mirror 30, the retroreflecting elements as retroreflective elements are placed at the projection positions corresponding to each of the predetermined images so that all the virtual images corresponding to the plurality of predetermined images can be seen at the same time. By arranging each of the

reflective sheets

32a and 32b, clear virtual images a and b of a plurality of predetermined images can be seen at the same time.

Further, the height Fa from one side of the second half mirror 30 to the projection plane of the retroreflective sheet 32a is longer than the height Fb from one side of the second half mirror 30 to the retroreflective sheet 32b. The reason why the virtual image b can be visually recognized behind the virtual image a is that the retroreflective sheet 32 a is arranged on the lower end side of the inclined surface of the second half mirror 30 . In this way, each of the virtual images a and b is retroreflected from one surface side of the second half mirror 30 corresponding to each of the virtual images a and b so that each of the virtual images a and b can be seen at different positions from the other surface side of the second half mirror 30 . By adjusting the heights Fa and Fb to the

retroreflective sheets

32a and 32b as the retroreflective elements, clear virtual images of a plurality of predetermined images can be seen at different positions at the same time.

In FIG. 12, a character "A" is projected from the holographic projector unit 10a (see FIG. 11) onto a projection surface (hereinafter simply referred to as a projection surface), which is the retroreflected light exit surface of the retroreflective sheet 32a. ” is projected, and the character “B” is projected as a projection image b onto a projection surface (hereinafter simply referred to as a projection surface), which is the retroreflected light exit surface of the retroreflective sheet 32b. The letter "A" projected onto the retroreflective sheet 32a appears as a virtual image a on the other side of the second half mirror 30, and the letter "B" is projected onto the projection surface of the retroreflective sheet 32b. , the character "B" as the virtual image b on the other side of the second half mirror 30 can be visually recognized on the back side of the character "A" as the virtual image a. In this way, the single holographic projector unit 10a can project the letters "A" and "B" from one side of the second half mirror 30 to the other side of the second half mirror 30 with different senses of distance. virtual images can be seen at the same time.

Here, when a mirror was placed instead of the

retroreflection sheets

32a and 32b in FIG. 11, the virtual images a and b could not be seen. It is presumed that this is due to the difference in reflection between the mirror and the retroreflective sheet. Also, when white paper or black paper was placed instead of the

retroreflective sheets

32a and 32b, the virtual images a and b were visible, but extremely unclear. It is presumed that the white paper or black paper has a lower reflectance in the direction of retroreflection than the retroreflective sheet.

Even if a light shielding plate 31 is inserted as shown in FIG. 13 between the virtual image a and the virtual image b shown in FIG. 11, the virtual image b can be visually recognized through the light shielding plate 31. Further, as shown in FIG. 14, by moving the retroreflective sheet 32b in the direction of the arrow f (the direction of the second half mirror 30) to the position 32b', the position where the virtual image b can be visually recognized is indicated by the arrow. It can be moved to f' (in the direction of the second half mirror 30) to a position b' in front of the virtual image a. However, when the retroreflective sheet 32b is moved, a computer-generated hologram (CGH) in which the projection image b is projected at the position 32b' shown in FIG. It is necessary to be

As shown in FIGS. 11 to 14, the positions at which the virtual images a and b can be visually recognized correspond to the distance (optical path length) between the

retroreflective sheets

32a and 32b and the second half mirror 30. The longer the distance (optical path length) to the half mirror 30 is, the more the virtual image can be visually recognized on the back side of the second half mirror 30 . When it is desired to increase the distance (optical path length) between the retroreflective sheet and the second half mirror 30, and there are physical restrictions such as the size of the room, the retroreflective sheet 32a shown in FIG. and the second half mirror 30 to bend the optical path between the retroreflective sheet 32a and the second half mirror 30 to increase the optical path length.

In the projection unit 10b shown in FIGS. 11 to 15, two retroreflective sheets are arranged, but in the projection unit 10b shown in FIG. 16, there is only one movable retroreflective sheet 32a. may Since the holographic projector section 10a irradiates the diffracted light so as to project the projected images a and b onto a predetermined position on one surface side (inclined surface) of the second half mirror 30, the retroreflective sheet shown in FIG. At the position 32 a , the projection image a is projected and the virtual image a can be visually recognized on the other side of the second half mirror 30 . When the retroreflection sheet 32a at the projection position of the projection image a is moved to the projection position 32a' where the projection image b is projected, the virtual image a disappears, but the projection image b is not projected onto the retroreflection sheet 32a. A virtual image b can be visually recognized on the other side of the second half mirror 30 . The virtual image b can be visually recognized on the back side of the virtual image a. By moving the retroreflective sheet 32a movably provided in this way to the position where the projected image b is projected, the virtual image b can be visually recognized with a perspective different from that of the virtual image a.

11 to 16, the

retroreflective sheets

32a and 32b are arranged in series at the lower end side and the upper end side of the second half mirror 30 as shown in FIG. The position of b is also affected by the tilt of the second half mirror 30 . In order to avoid such an influence due to the inclination of the second half mirror 30, as shown in FIG. is preferred. By arranging the

retroreflection sheets

32a and 32b in this way, as shown in FIG. It is possible to predict that the virtual images a and b can be visually recognized at the positions corresponding to the positions.

In the aerial projection device 10 described above, diffracted light is emitted from the holographic projector section 10a so that a predetermined image is projected at the projection position (focus position) of the CGH. Accurately knowing the focal position of this CGH is necessary to obtain a clear real or virtual image or a desired blurred real or virtual image. The focal position of CGH can be accurately known by a guide device that guides the projection object to a predetermined spatial position. This guide device includes a hologram formed with an interference pattern adjusted so that an image of a predetermined shape having a pattern with narrow gaps is imaged at a predetermined spatial position, and a projection target object guided to a predetermined spatial position. When the hologram is projected, the parallel light irradiated to the hologram is diffracted based on the interference pattern. A parallel light emitting means for emitting parallel light is provided. The guide method using this guide device uses a holographic projector whose imaging position is adjusted so that an image of a predetermined shape having a pattern with narrow gaps is projected at a predetermined spatial position, and is placed near this spatial position. When an image is projected from the holographic projector onto the projection target, the projection target is guided to a spatial position where the pattern of the image formed on the projection target matches the pattern of the image.

This guide device and guide method will be described in detail with reference to FIG. A guide device 70 shown in FIG. 18 is composed of a holographic projector section 10a and a stereoscopic screen 28 as a projection target mounted on a mounting table 75 so as to be slidable in the arrow F direction. The holographic projector section 10 a is composed of a personal computer (PC) 12 to which a tablet terminal device 11 is connected, a reflective spatial light modulator (SLM) 14 , a half mirror 22 and a parallel light emitting section 15 . The parallel light emitting section 15 is composed of a laser light emitting section 16 , an objective lens 18 and a plano-convex lens 20 . In the holographic projector unit 10 a , a cubic computer-generated hologram (CGH) having a pattern of narrow gaps is calculated by the CGH calculation unit 17 of the PC 12 as a predetermined image input from the tablet terminal device 11 and displayed on the SLM 14 . The interference fringes of the hologram displayed on the SLM 14 are interference information whose projection position (focal position) is calculated such that a cube as a predetermined image is projected at a predetermined spatial position. Parallel light is applied to the display surface of the SLM 14 on which such interference fringes are displayed. This parallel light is emitted from the laser light emitting portion 16 of the parallel light emitting portion 15. After being condensed once by the objective lens 18, the parallel light spreads, becomes parallel light by the plano-convex lens 20, and is converted into parallel light by the half mirror 22 on the display surface of the SLM 14. is the light reflected in the direction of The parallel light irradiated to the display surface of the SLM 14 becomes diffracted light based on the interference information of the hologram displayed on the display surface, emerges from the display surface of the SLM 14, passes through the half mirror 22, and passes through the half mirror 22. It is projected onto the stereoscopic screen 28 .

The three-dimensional screen 28 has a cubic shape, as shown in FIG. 18(a), and is formed by attaching a white sheet to a frame. The three-dimensional screen 28 is supported by support rods 73 on a support base 74 which is slidably placed on a mounting base 75 in the direction of arrow F. 18(a), two side surfaces of the three-dimensional screen 28 on the support base 74 shown in FIG. 18(a) are projected from the holographic projector section 10a. The 3D screen 28 is slidably mounted on the mounting table 75, and is adjusted to be a projection surface on which images of the corresponding two surfaces of the cube are projected. A cubic image with a pattern of narrow gaps is projected from the holographic projector unit 10a located on the left side of the holographic projector unit 10. This image is input from the tablet-type terminal device 11. When the pattern matches the pattern projected on the stereoscopic screen 28, it is found that the stereoscopic screen 28 is positioned at the projection position (focus position) of the holographic projector section 10a.

The narrow gap pattern may be a pattern consisting of a plurality of thin lines and dots at predetermined intervals, for example, the projection plane of the stereoscopic screen 28 positioned at the projection position (focal position) of the holographic projector section 10a (Fig. 18 ( a) If the angles of the three-dimensional screen 28 shown in (b) are A, B, B', A', C', and C, then sides AB, sides BB', sides B'-A', sides A'-C' side C'-C, the plane surrounded by side CA)), a plurality of thin straight dotted lines as shown in FIG. 18(b) are formed through narrow gaps. It is preferable that the dotted line pattern 76 is projected. As shown in FIG. 18(a), when the three-dimensional screen 28 is placed on the mounting table 75 so that the side AA' is closest to the holographic projector section 10a, the diffraction from the holographic projector section 10a is A dotted line pattern 76 projected on the projection surface of the white sheet of the stereoscopic screen 28 by irradiation of light appears as shown in FIG. If the thin straight dotted lines forming the dotted line pattern 76 can be clearly discerned over the entire projection surface of the stereoscopic screen 28, it means that the stereoscopic screen 28 is located at the projection position (focus position) of the holographic projector section 10a. I understand. On the other hand, when the stereoscopic screen 28 is located farther than the projection position (focus position) of the holographic projector unit 10a, the projection plane of the stereoscopic screen 28 is viewed from the direction of projection of the diffracted light, as shown in FIG. 18(c). 18B, a slanted line pattern 77 different from the dotted line pattern 76 in FIG. 18B can be visually recognized. Further, even when the stereoscopic screen 28 is positioned closer to the holographic projector unit 10a than the projection position (focus position) of the holographic projector unit 10a, when the projection plane of the stereoscopic screen 28 is viewed from the direction of projection of the diffracted light, As shown in FIG. 18(c), a slanted line pattern 77 different from the dotted line pattern 76 in FIG. 18(b) can be visually recognized. From the pattern of the dotted line pattern 76 projected onto the projection surface of the stereoscopic screen 28 in this way, it can be easily determined whether or not the stereoscopic screen 28 is positioned at the projection position (focus position). Can be guided to the projection position (focus position).

When a predetermined image is projected onto the flat screen 36 as shown in FIG. 3 or the

retroreflective sheets

32a and 32b as shown in FIG. A dotted line pattern 78 in which a plurality of thin dotted lines are formed at narrow intervals is preferable. As shown in FIG. 19(a), when the thin straight dotted lines forming the dotted line pattern 78 can be clearly discerned over the entire projection surface of the screen 36 or the retroreflective sheet 32, the screen 36 or the retroreflective sheet 32 can be clearly identified. It can be seen that the sheet 32 is positioned at the projection position (focus position) of the holographic projector section 10a. On the other hand, as shown in FIG. 19B, when an inclined line pattern 79 different from the dotted line pattern 78 in FIG. It can be seen that it is installed at a position distant from the focal position). Therefore, by moving the screen 36 or the retroreflective sheet 32 to the position where the dotted line pattern 78 shown in FIG.

The guide device 70 shown in FIG. 18 can be used for a personal identification device, for example, a personal identification device using the iris of the human eye as shown in FIG. The device shown in FIG. 20 is used for determining the position of a subject for an iris-based personal identification device. In the position determining apparatus shown in FIG. 20, an image having a pattern of narrow gaps is projected onto the subject's forehead from the holographic projector unit 10a. The image projected on the subject's forehead is captured by the camera 80 and displayed on the display device 82 so that the subject can see it. When the image projected on the subject's forehead matches the pattern of the image input from the tablet terminal device 11, the subject's eyes are within the depth range of the iris imaging camera (not shown). The image having the narrow gap pattern may be a narrow gap pattern, for example, a dotted line pattern 78 in which a plurality of thin dotted lines are formed with narrow gaps, as shown in FIG. 19(a). When the pattern projected on the subject's forehead, photographed by the camera 80 and displayed on the display device 82 is the dotted line pattern 78 shown in FIG. not shown), and the subject's iris can be imaged by the iris imaging camera. On the other hand, when the pattern displayed on the display device 82 is the slanted line pattern 79 as shown in FIG. The face is moved to a position where the pattern displayed on the display device 82 becomes the dotted line pattern 78 shown in FIG. 19(a). 20, when the dotted line pattern 78 is projected from the holographic projector unit 10a onto the subject's forehead, if there is a risk that the diffracted light from the SLM 14 may enter the subject's eyes, the SLM 14 is equipped with a light emitting diode (LED). Light may be applied, or infrared light that is invisible to humans but recognizable by the camera 80 may be applied.

Also, the guide device 70 shown in FIG. 18 can be used as a personal authentication device using a hand vein as shown in FIG. The device shown in FIG. 21 is used to determine the position of the subject's hand in a vein personal identification device. In the position determining apparatus shown in FIG. 21, when the subject's hand is extended onto the vein imaging camera 84, an image having a pattern of narrow gaps is projected onto the arm from the holographic projector unit 10a. The image projected on the subject's arm can be directly viewed by the subject, and when the pattern of the image input from the tablet-type terminal device 11 matches, the subject's hand falls within the depth range of the vein imaging camera 84. ing. The image having the pattern of narrow gaps may be a pattern of narrow gaps, for example, a dotted line pattern 78 in which a plurality of fine lines are formed with narrow gaps, as shown in FIG. 19(a). When the pattern projected on the subject's arm becomes a slanted line pattern 79 as shown in FIG. First, the subject moves the hand and arm vertically to a position where the pattern displayed on the arm becomes the dotted line pattern 78 shown in FIG. 19(a). In the apparatus shown in FIG. 21, the SLM 14 may be irradiated with laser light so that the diffracted light from the SLM 14 does not enter the subject's eyes and the pattern projected onto the arm is made clear.

In the aerial projection device 10 described above, a computer-generated hologram (CGH) of a predetermined image input from the tablet terminal device 11 to the PC 12 is calculated by the CGH calculator 17 and output to the SLM 14 . A computer-generated hologram (CGH) calculated by the CGH calculator 17 will be described. A computer-generated hologram (hereinafter simply referred to as CGH) of a three-dimensional object composed of N object points shown in FIG. The light intensity I _comp (x _h , y _h , 0) at each point (x _h , y _h , 0) is given by the following formula (3)

can be expressed as

By the way, the SLM 14 includes one that displays an amplitude hologram and one that displays a phase hologram. Here, as shown in FIG. 22, the position coordinates of the _n -th point light source on the three-dimensional object are P( _xn , _yn , _zn ), its brightness is An, and the size of one pixel is Δ _x ×Δ _y , if the coordinates of the i-th and j-th CGH pixels in the x and y directions are (x _h , y _h )=(iΔ _x , jΔ _y ), each point on the amplitude hologram (x _h , _y _h ,0) is _obtained by the _following formula (4)

can be expressed as

Also, the phase I _phase (x _h , y _h , 0) at each point (x _h , y _h , 0) on the phase hologram is expressed by the following formula (5)

can be expressed as
Im{I _comp } in the above equation (5) is the imaginary part, Re{I _comp } is the real part, and the above equation (4)
is the same as, the above formula (3) becomes the following formula (6)

can be expressed as

The amplitude hologram can be calculated based on the above equation (4), and the phase hologram can be calculated based on the above equation (6), which can be used for CGH calculation of a three-dimensional still image.
However, in the case of 3D moving images, a further improvement in calculation speed is required compared to the CGH calculation using the above formula (4) or the above formula (6). Therefore, in order to improve the calculation speed of CGH, the above formula (4) representing the light intensity of the amplitude hologram (I _amp (x _h , y _h , 0)) is changed to the following formula (7)

transformed like
Also, the above formula (6) representing the phase of the phase hologram (I _phase (x _h , y _h , 0)) is changed to the following formula (8)

transformed like

In order to calculate the amplitude hologram based on the above formula (7) in the CGH calculation unit 17 of the PC 12 of the aerial projection device 10, as shown in FIG. A position coordinate data storage unit 17a for storing position coordinate data of a point light source of a three-dimensional image, and values obtained by calculating sinX and cosX in the x direction of the CGH based on the position coordinate data in the position coordinate data storage unit 17a are stored. a CGH x-direction trigonometric function table 17b; a CGH y-direction trigonometric function table 17c that stores values obtained by calculating sinY and cosY in the CGH y-direction based on the position coordinate data in the position coordinate data storage unit 17a; An amplitude hologram calculator 17d that calculates the light intensity (I _amp (x _h , y _h , 0)) of the amplitude hologram using the trigonometric function values stored in the trigonometric function tables 17b and 17c, and the amplitude hologram calculator 17d An amplitude hologram data storage unit 17e is provided for storing the calculated light intensity (I _amp (x _h , y _h , 0)) of the amplitude hologram and outputting it to the SLM 14 .

FIG. 24 shows a pseudo code for calculating the amplitude hologram in the CGH calculator 17 shown in FIG. 23, and FIG. 25 shows its flow chart. The pseudo code shown in FIG. 24 assumes that the CGH resolution is W×H, and the flowchart shown in FIG. 25 is for a 3D moving image, but it can also be applied to a 3D still image.
24 and 25, the trigonometric function table 17c is created after creating the trigonometric function table 17b, but the trigonometric function table 17b may be created after creating the trigonometric function table 17c. 17b and 17c may be created in parallel. The creation of the trigonometric function tables 17b and 17c, the calculation of the amplitude hologram by the amplitude hologram calculator 17d, and the output of the amplitude hologram to the SLM 14 by the amplitude hologram data storage unit 17e may be processed in parallel. Furthermore, when the trigonometric function tables 17b and 17c are created in advance for each frame of the three-dimensional moving image, and the amplitude holograms to be displayed on the SLM 14 can be created and displayed by using them, the point light source loop is the first in the flowchart shown in FIG. It may be an inner loop.

In order to calculate the phase hologram based on the above formula (8) in the CGH calculation unit 17 of the PC 12, points of the three-dimensional image input from the tablet terminal device 11 are stored in the CGH calculation unit 17 as shown in FIG. A position coordinate data storage unit 17a for storing position coordinate data of the light source, and a CGH x direction triangle for storing values obtained by calculating sinX and cosX in the x direction of the CGH based on the position coordinate data in the position coordinate data storage unit 17a. A function table 17b, a CGH y-direction trigonometric function table 17c storing values obtained by calculating sinY and cosY in the CGH y-direction based on the position coordinate data of the position coordinate data storage unit 17a, and trigonometric function tables 17b and 17c The imaginary/real part calculator 17f that calculates the imaginary part Im{Icomp} and the real part Re{Icomp} using the trigonometric function values stored in the imaginary/real part calculator 17f, and The imaginary/real part storage unit 17g of the imaginary part Im{Icomp} and the real part Re{Icomp}, and the imaginary/real part Im{Icomp} and the real part Re{Icomp} stored in the imaginary/real part storage unit 17g are stored as A phase hologram calculator 17h that calculates the phase of the phase hologram (I _phase (x _h , y _h , 0)) using the phase hologram calculator 17h, and the phase hologram calculated by the phase hologram calculator 17h (I _phase (x _h , y _h ,0)) and outputs it to the SLM 14 is provided.

Pseudo code for calculating the phase hologram in the CGH calculator 17 shown in FIG. 26 is shown in FIG. 27, and its flow chart is shown in FIG. The pseudo code shown in FIG. 27 assumes that the CGH resolution is W×H, and the flowchart shown in FIG. 28 is for a 3D moving image, but it can also be applied to a 3D still image.
27 and 28, the trigonometric function table 17c is created after the trigonometric function table 17b is created, but the trigonometric function table 17b may be created after the trigonometric function table 17c is created. 17b and 17c may be created in parallel. In addition, the trigonometric function tables 17b and 17c are created, the imaginary part Im{Icomp} and the real part Re{Icomp} are calculated in the imaginary/real part calculator 17f, and the phase hologram phase is calculated in the phase hologram calculator 17h. The calculation of (I _phase (x _h , y _h , 0)) and the output of the phase hologram from the phase hologram data storage unit 17i to the SLM 14 may be processed in parallel. Furthermore, when the trigonometric function tables 17b and 17c are created in advance in each frame of the three-dimensional moving image, and the phase hologram to be displayed on the SLM 14 can be created and displayed by using them, the point light source loop is the first in the flowchart shown in FIG. It may be an inner loop.

The CGH calculation unit 17 for calculating the amplitude hologram based on the above formula (7) or calculating the phase hologram based on the above formula (8) is implemented by a CPU (Central Processing Unit) and/or a GPU (Graphics Processing Unit). Unit).
By the way, both CPU and GPU have a plurality of cores, but in order to realize real-time reproduction of 3D moving images, at least 30 CGHs must be calculated per second and reproduced. However, the number of cores that a CPU has is much smaller than that of a GPU, and the processing speed of the CPU is slow. Although it can be used for processing 3D still images, it is not suitable for processing 3D moving images. On the other hand, a GPU has many cores and can be used not only for processing 3D still images but also for 3D moving image processing.

In the explanation so far, the case where there is one projection unit 10b has been explained, but a plurality of projection units may be installed. FIG. 30 shows a case where three projection units 10b shown in FIG. 3 are installed. 30A, the projection units 10b-1, 10b-2, and 10b-3 are arranged in series so that real images are formed on the same surface side of the second half mirror 30. In FIG. A flat screen 36 is mounted on each frame 26, and each screen 36 is diffracted from a hologram having a different figure from the holographic projector unit 10a (not shown) shown in FIG. 1(a). Light 1, diffracted light 2, and diffracted light 3 are irradiated. A circular image 36a-1 shown in FIG. 30(b) is projected onto the screen 36 irradiated with the diffracted light 1, and an image 36a-1 shown in FIG. 30(b) is projected onto the screen 36 irradiated with the diffracted light 2. A circular image 36a-2 having a diameter smaller than that of the circular image 36a-1 is projected onto the screen 36 irradiated with the diffracted light 3, as shown in FIG. A circular image 36a-3 having a smaller diameter than the image 36a-2 is projected. Circular images 36a-1, 36a-2 and 36a-3 projected onto each screen 36 are formed as real images 38-1, 38-2 and 38-3 in the space on one side of each second half mirror 30. image. When viewed from the real image 38-1 side, these real images 38-1, 38-2, and 38-3 appear concentric as shown in FIG. 30(c). By arranging a plurality of projection units 10b in this way, a complicated real image can be formed in the air. Diffracted light 1, diffracted light 2, and diffracted light 3 shown in FIG. 30 may be emitted from the same holographic projector unit, or may be emitted from different holographic projector units. 30 uses a flat screen 36, but by using a three-dimensional screen 28 as shown in FIG. 1, a complex real image formed in the air can be viewed from multiple angles. Although three retroreflective sheets 32 are used in FIG. good.

The frame 26 on which the screens of the three projection units 10b-1, 10b-2, and 10b-3 shown in FIG. 30 are mounted has the same height, but as shown in FIG. By moving the frame 26 in the vertical direction, the screen 36 also moves in the vertical direction, and the real image formed in the air moves in the horizontal direction to come into contact with or separate from the real image on the other stage. In FIG. 31, the two projection units 10b-1 and 10b-2 shown in FIG. 30 are arranged in series so that real images 38-1 and 38-2 are formed in the air on the same side of the second half mirror 30. It is A flat screen 36 is mounted on each frame 26, and each screen 36 is diffracted from a hologram having a different figure from the holographic projector unit 10a (not shown) shown in FIG. 1(a). Light 1 and diffracted light 2 are irradiated, and real images 38 - 1 and 38 - 2 are formed on one surface side of each second half mirror 30 . Here, the frame 26 of the projection unit 10b-2 is raised to the upper position 26-1, and the projection position (focus position) of the holographic projector unit is aligned with the screen 36-1 moved to the position 26-1. Then, the formed real image 38-2' moves to the right (in the direction of the arrow f-1) from the real image 38-2 and is separated from the real image 38-1 of the projection unit 10b-1. On the other hand, when the frame 26 of the projection unit 10b-2 is lowered to the lower position 26-2 and the projection position (focus position) of the holographic projector unit is aligned with the screen 36-2 moved to the position 26-2. , the formed real image 38-2″ moves to the left (arrow f-2 direction) of the real image 38-2 and approaches the real image 38-1 of the projection unit 10b-1. By vertically moving the frame 26 on which the screen 36 of 10b is mounted, the real image 38 of the projection unit 10b moved in the left-right direction can come into contact with or separate from another real image 38, and the real image can move in various ways. 31, only the frame 26 of the projection unit 10b-2 is vertically moved, but by moving the frame 26 of the projection unit 10b-1 together, the projection unit 10b- The real image 38-1 of 1 can also be moved in the left-right direction so that it overlaps with the real image 38-2 of the projection unit 10b-2, or the real image 38-1 can be moved behind the real image 38-2. However, although two retroreflective sheets 32 were used, one retroreflective sheet 32 may be used as long as it is large enough to cover the two second half mirrors 30. Note that FIG. Although the planar screen 36 has been described above, the 3D screen 28 can similarly give various movements to the real image.

In the above description, a reflective SLM was used as the SLM 14, but a transmissive SLM may be used. may be entered. Further, although the computer-generated hologram calculated by the PC 12 is displayed on the SLM 14, the hologram interference fringes may be printed on a film. Further, although the SLM 14 is irradiated with laser light, it may be irradiated with light from a light emitting diode (LED).

Examples of the present invention will be described in detail below, but the scope of the present invention is not limited to these examples.

(Example 1)
The visible light transmittance and diffusivity of the screen material are measured.
(measuring device)
A measuring apparatus shown in FIG. 10 was used. in the measuring device,
Light source 50: emits green laser light (wavelength: 532 nm) Hole diameter of hole 58: 2.5 cm
Light meter: Laser power meter (LP1 manufactured by Sanwa Electric Instrument Co., Ltd.)
Distance L: 1m
Distance M: When measuring transmittance: 0 cm
When measuring diffusivity: 15 cm

(Screen material)
The screen materials used for the measurements are shown in Table 1 below. All the screen materials shown in Table 1 are white.

(Measurement of transmittance)
For each of the screen materials shown in Table 1, the transmittance of irradiated visible light along the optical axis was measured. For the measurement, as described above, the hole 58 is irradiated with parallel light of green laser light (wavelength 532 nm) emitted from the light source 50 shown in FIG. A laser power meter was used to measure the amount of received light _T0 when the holes 58 were not closed with the screen material. Next, a screen material was attached so as to block the holes 58, and a laser power meter was installed at a position (M = 0 cm) where the light receiving surface 62 faced the holes 58, and the transmitted light transmitted through the holes 58 and the screen material is measured. Let (T/T ₀ )×100 be the transmittance. The transmittance of each screen material shown in Table 1 is shown in Table 2 below.

(Measurement of diffusivity)
The amount of received light was measured by rotating the light receiving surface 62 of the laser power meter shown in FIG. The distance between the light-receiving surface 62 of the laser power meter and the screen material attached to the hole 58 was always kept at 15 cm (rotating radius of the light-receiving surface 62: 15 cm). The amount of received light measured at a position where the light receiving surface 62 is rotated by an angle ±θ with respect to the optical axis 51 is the amount of diffused light (T') transmitted through the screen material and diffused by an angle ±θ with respect to the optical axis 51. . The diffusivity at an angle ±θ with respect to the optical axis 51 is represented by the ratio (T'/T ₁ ) to the amount of light received (T ₁ ) measured at a position with an angle of 0° (M=15 cm). The diffusivity of each screen material shown in Table 1 is shown in Table 2 below.

(Example 2)
A three-dimensional screen 28 shown in FIG. 1(b) was produced using the screen materials shown in Table 1, and characters and patterns of "Kochi" were drawn. The stereoscopic screen 28 was placed in a bright room (527 lux (lx)), and the aerial projection apparatus 10 shown in FIG. As the retroreflective sheet 32, an aerial display reflector RF-Ax manufactured by Nippon Carbide Industry Co., Ltd. is used. The distance M to the intermediate point was set to 15 cm. A green laser beam (wavelength: 532 nm) was emitted from the parallel light emitting portion 15 .
Furthermore, in a dark room (0.03 lux (lx)) in which the room lights were turned off and the windows were covered with light-shielding curtains, observation was carried out with the naked eye in the same manner as in the bright room. The results are shown in Table 3 below. In Table 3, (++) is indicated when the real image 34 is "clearly visible", (+) is indicated when "identifiable", and (±) is indicated when "not clearly visible".
The illuminance of the room was measured with an illuminometer (T-10A (trade name)) manufactured by Konica Minolta Japan, Inc.

As is clear from Tables 2 and 3, No. The screen materials 5, 9, and 11 have a transmittance at the optical axis of less than 47%, and the real image 34 is "not well visible" (±) in the air in a bright room. This is because the amount of light transmitted through the stereoscopic screen 28 has decreased.
On the other hand, No. The screen materials 1 to 4, 6 to 8, 10, and 12 to 15 had a transmittance of 47% or more on the optical axis, and a real image 34 could be seen in the air even in a bright room. These are the three-dimensional screens 28 having a transmitted light amount of No. This is because it increased more than 5, 9, and 11 screen materials. In particular, No. The

screen materials

10, 13, and 15 (thin paper, tengu paste (18 g/m ² ), thin Mino 3 momme) have a transmitted light amount of 55 to 65% on the optical axis of the three-dimensional screen 28, and the light Since the diffusivity over the entire range of -10° to +10° with respect to the axis is also 15% or more, even in a bright room, the letters and patterns of "Kochi" in the real image 34 could be clearly seen. When the stereoscopic screen 28 has both high transmittance and high diffusivity, a virtual image (corresponding to the virtual image 39 shown in FIG. 5A) generated by specular reflection of the diffused light irradiated to the retroreflective sheet 32 is generated. This is because the real image 34 has become less visible and easier to see. When the diffusion rate of the stereoscopic screen 28 is high, the diffused light diffused over a wide range from the projection point 29a of the stereoscopic screen 28 shown in FIG. On the other hand, it is presumed that the specular reflected light from the retroreflective sheet 32 spreads out, making the virtual image difficult to see.
On the other hand, No. 1 to 4, 6 to 8, and 14, a virtual image (corresponding to the virtual image 39 shown in FIG. 5(a)) superimposed on the real image 34 was also visible, but as shown in FIG. By tilting, the virtual image could be moved out of the field of view.
In such a bright room (527 lux (lx)), the real image 34 was judged to be "distinguishable" (+) or "not well visible" (±). 2, 5, 6, 9, 11, and 12, the real image 34 is "well visible" (++) in a dark room (0.03 lux (lx)).

(Example 3)
In Example 2, the screen material No. 2 was evaluated as "poorly visible" (±) for the real image 34 in a bright room (527 lux (lx)). 5 (cotton (plain lawn)), No. 9 (machine paper (machine-made paper)), No. 11 (Tengu paste: basis weight 34 g/cm ² )), and No. 1 in Table 1. Each of the screen materials of diffusion plates 16 to 22 was made into a flat screen, and the words "Kochi" were written on this screen to obtain a screen 36 shown in FIG. 3(a). Using this screen 36, it was visually observed whether or not a real image 38 of characters "Kochi" could be visually recognized in the air from the front by the aerial projector shown in FIG. 3(a) in a bright room (527 lux (lx)). As a result, as shown in Table 4 below, the real image 38 of the characters "Kochi" was "clearly visible" (++) on the entire screen.

(Example 4)
The CGH calculation unit 17 of the PC 12 shown in FIG. 1 was provided in the CPU or GPU, and the CGH creation speed depending on the difference in the CGH calculation formula of the amplitude hologram was measured by changing the number of object points. The results are shown in Table 5 below.
Calculation formula for amplitude hologram Equation (4) above [pseudocode: FIG. 29(a)]
Equation (7) above [pseudocode: FIG. 24]
CGH calculator 17
CPU: Core (trademark) i7-8700K manufactured by INTEL Corporation
GPU: GeForce RTX™ 3080 from NVIDIA Corporation

As is clear from Table 5, the CGH creation speed by Equation (7) is faster than Equation (4), and the CGH creation speed of GPU is considerably faster than that of CPU. can be applied to 3D moving images.
Here, when the calculation of formula (4) is performed by the CPU, the calculation load of the cos function becomes large. A cos table with 8-bit integer values from -127 to 127 was used to speed up the calculation. Also, Intel C++ compiler classic Version 2021.2.0 (option: -O3 -xCORE-AVX2 -qopenmp) was used as a compiler, and the number of OpenMP threads was set to 12.

(Example 5)
The CGH calculation unit 17 of the PC 12 shown in FIG. 1 was provided in the CPU or GPU, and the CGH creation speed depending on the difference in the CGH calculation formula of the phase hologram was measured by changing the number of object points. The results are shown in Table 6 below.
Calculation formula for phase hologram Equation (6) above [pseudocode: FIG. 29(b)]
Equation (8) above [pseudocode: FIG. 27]
CGH calculator 17
CPU: Core (trademark) i7-8700K manufactured by INTEL Corporation
GPU: GeForce RTX™ 3080 from NVIDIA Corporation

As is clear from Table 6, the CGH creation speed by Equation (8) is faster than Equation (6), and the CGH creation speed of GPU is considerably faster than that of CPU. It can be seen that it can be applied to three-dimensional moving images.
Here, when the calculation of formula (6) is performed by the CPU, the calculation load of the cosine and sin functions becomes large. Calculation speed was increased using cos and sin tables in which 1 to +1 are integer values of -127 to 127 of 8 bits. Also, Intel C++ compiler classic Version 2021.2.0 (option: -O3 -xCORE-AVX2 -qopenmp) was used as a compiler, and the number of OpenMP threads was set to 12.

The aerial projection device according to the present invention can be used as an aerial projection device capable of forming an image of an elevator button in the air, or an aerial projection device capable of forming a predetermined image in the air for education, games, and the like.

10: aerial projection device, 10a: holographic projector unit, 10b, 10b-1, 10b-2, 10b-3: projection unit, 11: tablet terminal device, 12: personal computer, 14: spatial light modulator (SLM ), 15: parallel light emitting section, 16: laser beam emitting section, 17: CGH calculation section, 17a: position coordinate data storage section, 17b, 17c: trigonometric function table, 17d: amplitude hologram calculation section, 17e: amplitude hologram data Storage unit 17f: Imaginary part/real part calculation unit 17g: Imaginary part/real part storage unit 17h: Phase hologram calculation unit 17i: Phase hologram data storage unit 18, 52: Objective lens 20, 54: Flat Convex lens, 22: first half mirror, 24, 35: mirror, 26: frame, 26', 26-1, 26-2: position of frame 26, 27, 74: support, 28: three-dimensional screen, 28a : projection image of cube 28b: frame 28c: Japanese paper 29a, 29b, 37a, 37b, 37a', 37b', 40a, 40b, 40a', 40b': projection point 30: second half mirror 31: Light shielding plate 32, 32a, 32b: retroreflective sheet 32': position of retroreflective sheet 32 32b': position of retroreflective sheet 32b 32a': projection position 33a: reflective sheet 33b: glass Beads 33c: transparent resin layer 34, 38, 38', 38-1, 38-2, 38-3, 38-2', 38-2'': real images 34a, 34b, 38a, 38b, 38a', 38b': image forming point, 36, 36-1, 36-2: screen, 36a, 36a', 36a-1, 36a-2, 36a-3, 40, 40': projection image, 39, 39', 39 '', 42, 42': virtual images, 39a, 39a': corresponding points of the imaging point 38a, 39b, 39b': corresponding points of the imaging point 38b, 42a, 42b, 42a', 42b': projection points, 40a, Corresponding points of 40b, 40a' and 40b', 50: light source, 51: optical axis, 56: plate-like body, 58: hole, 60: measurement object, 62: light receiving surface, 62': position, 70: guide device, 73: support rod, 75: mounting table, 76, 78: dotted line pattern, 77, 79: inclined line pattern, 80: camera, 82: display device, 84: vein imaging camera, A, B, C, A', B', C': corners of the three-dimensional screen 28, F: sliding direction of the support base 74, F-1, F-2: moving direction of the frame 26, F': turning direction of the three-dimensional screen 28 in the horizontal plane, Fa, Fb: height, Fa', Fb': depth, L, M: distance , F″: rotation direction of the stereoscopic screen 28 in the vertical plane, f: movement direction of the retroreflective sheet 32b, f-1, f-2: movement direction of the real image 38-2, f′: movement of the virtual image b. direction, b': moving position of virtual image b, θ: angle, W: number of horizontal pixels of CGH, _H : number of vertical pixels of CGH, xh: x-direction position coordinates of pixels on hologram, _yh : y-direction position coordinates of pixels on the hologram, Δx: pixel size in _x -direction, Δy: pixel size in _y -direction, P( _xn, yn _, zn): _n of three-dimensional object position coordinates of the th object point P

Claims

A holographic projector unit that emits diffracted light obtained by diffracting the irradiated parallel light based on interference information of a hologram of a predetermined image, a screen that is irradiated with the diffracted light and projects the predetermined image, and the diffraction a half mirror installed at a position where transmitted diffused light that has passed through the screen and diffused out of the light is irradiated so as to be inclined with respect to the diffracted light irradiated onto the screen; and transmitted light from the half mirror or and a projection unit composed of a retroreflective element irradiated with reflected light,
The transmitted light or the reflected light of the half mirror of the transmitted diffused light is retroreflected by the retroreflective element, emitted in the opposite direction along the original incident path, and reflected by the half mirror or the half mirror. An aerial projection apparatus, wherein a real image of the predetermined image is formed in the air on one side of the half mirror by transmitted light that has passed through a mirror.
2. The aerial projection according to claim 1, wherein said screen is arranged at a position forward or rearward of a predetermined position projected on the basis of interference information of said hologram so that said real image appears blurred. Device.
The retroreflective element is tilted so that a virtual image corresponding to the real image viewed on the other side of the half mirror moves out of the field of view due to specular reflection of the retroreflective element. The aerial projection device according to claim 1.
Diffracted light diffracted based on interference information of each hologram of at least two predetermined images is emitted from the holographic projector unit,
The screen is irradiated with the diffracted light based on the interference information of one of the predetermined images, and the real image of one of the predetermined images is formed in the air via the half mirror and the retroreflective element. ,
The diffracted light based on the interference information of the other of the predetermined image is transmitted through the half mirror without being irradiated to the screen, and is irradiated to the retroreflected light exit surface of the retroreflective element, thereby forming the predetermined image. The other image is projected, and the retroreflected light emitted from the retroreflected light exit surface is reflected by the half mirror, causing the other of the predetermined images to be projected in the air on the side opposite to the reflecting surface of the half mirror. 2. The aerial projection device according to claim 1, wherein a virtual image of is visible.
The screen and/or the retroreflective element are arranged at a position forward or rearward of a predetermined position projected based on the interference information of the hologram so that the real image and/or the virtual image appear blurred. 5. The aerial projection device according to claim 4, characterized in that:
The aerial projection device according to claim 1, wherein the screen is a stereoscopic screen.
The aerial projection device according to claim 1 or claim 6, wherein the screen is made of Japanese paper or non-woven fabric.
At least two pairs of the half mirror and the screen are provided, and the two pairs are arranged in series with a predetermined interval so that the real image is formed in the air on the same side of each of the half mirrors. 2. The aerial projection device according to claim 1, wherein the aerial projection device is installed.
The screen on which a projected image corresponding to one of the real images is projected from the holographic projector unit is in contact with the half mirror such that at least one of the real images moves in a contacting/separating direction with respect to the half mirror. 9. The aerial projection device according to claim 8, wherein the aerial projection device is provided so as to be movable in a separation direction.
2. The hologram according to claim 1, wherein said hologram is a computer-generated hologram, and a spatial light modulator is provided for modulating said parallel light into diffracted light based on interference information of said computer-generated hologram. Aerial projection device.
The computer-generated hologram is an amplitude hologram, and the amplitude hologram is represented by the following formula (1)

11. The aerial projection device of claim 10, wherein the aerial projection device is calculated based on .
The computer-generated hologram is a phase hologram, and the phase hologram is represented by the following formula (2)

11. The aerial projection device of claim 10, wherein the aerial projection device is calculated based on .