Aerial image display method, wavelength dispersion correction method, aerial image display device, and wavelength dispersion correction device

Abstract

To prevent deterioration in display performance, such as reduction in contrast due to light scattering due to the structure of an imaging element, and generation of a virtual image, in an aerial image display device having an imaging optical path in which an optical path between a display device screen as a projection object and an image thereof is symmetrical with respect to the imaging element surface.SOLUTION: Disclosed is an aerial image display device 10 in which an optical path between a display device screen 11A as a projection object and an image thereof has an imaging optical path which is symmetrical with respect to an imaging element surface 13A and which includes a first wavelength dispersion element 12 and a second wavelength dispersion element 14 which generate the equivalent wavelength dispersion arranged at symmetrical positions of the imaging element surface 13A. A spatial image 15 is displayed through the first wavelength dispersion element 12 and the second wavelength dispersion element 14.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an aerial image display method and a wavelength dispersion correction method that enable the observation of a background object in a spatial image display device having an imaging optical path in which the optical path between the display screen, which is the projection object, and its image is symmetrical with respect to the imaging element surface, as well as an aerial image display device and a wavelength dispersion correction device. [Background technology]

[0002] Several aerial displays that display two-dimensional images in the air have been proposed. For example, Non-Patent Document 1 proposes an interface in which a weak diffusion film is placed on a beam splitter that serves as a tabletop in aerial imaging by retro-reflection (AIRR) using a flat panel display as a light source and a retro-reflection element, and an image is projected onto the tabletop. The position of the user's hands is acquired by a three-dimensional camera, and an aerial image is formed between the hands.

[0003] Furthermore, Non-Patent Document 2 proposes Haptoclone (Hapic & optical clone), which allows two people in different locations to interact with each other using their bare hands and eyes by interacting through a three-dimensional "clone" of tactile and visual information.

[0004] However, these devices have a projection light path installed in the background of the aerial image, and to prevent this from being observed, the area other than the aerial image is left dark. On the other hand, there is a demand for the ability to view the aerial image while observing the background, as depicted in science fiction movies. For this reason, Non-Patent Document 3 proposes a display device that displays aerial images with a see-through function by adopting an optical element called a dihedral corner reflector array (DCRA), which is used in aerial video systems and aerial interaction systems, instead of the optical elements used in existing HMDs.

[0005] However, this display device suffers from issues such as reduced contrast due to light scattering caused by the structure of the DCRA, the element responsible for image formation, and reduced display performance due to the generation of stray light components in direct light mode that passes without reflection and virtual images that are not aerial images and are generated by a single reflection in addition to the image-forming light in twice reflection mode that is emitted from the light source through the DCRA, as well as reduced freedom of structural design due to the imaging conditions of the DCRA.

[0006] On the other hand, a display device has been proposed that uses a display and two holographic optical elements (HOEs) to observe a virtual image 304 of an image produced by the display. A holographic diffraction element generates wavelength dispersion with a dispersion angle according to the wavelength, but a method has also been proposed in which the wavelength dispersion generated by the holographic diffraction element is corrected by a diffractive optical element (DOE) and a diffuser (see Non-Patent Document 4).

[0007] The hologram diffraction element in the display device is replaced with a diffractive optical element and a diffuser, and a virtual image of an image projected by a projector is observed instead of the display.

[0008] However, in this type of display device, although a good virtual image can be observed by correcting the wavelength dispersion, it is not possible to display a real image while correcting the wavelength dispersion. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Yutaka Tokuda, et. Al., SA'15 Emerging Technologies, November 02 - 06, 2015, Kobe, Japan., ACM 978-1-4503-3925-4 / 15 / 11. [Non-patent document 2] Yasutoshi Makino, et. al., CHI '16: Proceedings of the 2016 CHI Conference on Human Factors in Computing Systems, May 2016 Pages 1980-1990 [Non-patent document 3] AH2018, February 7-9, 2018 “Air Mounted Eyepiece: Optical See-Through HMD Design with Aerial Optical Functions” [Non-patent document 4] OPTICS EXPRESS Vol. 26, No. 19, p.24864, 2018, Off-axis virtual-image display and camera by holographic mirror and blur compensation, Tomoya Nakamura, Shinji Kimura, Kazuhiko Takahashi, Yuji Aburakawa, Shunsuke Takahashi, Sshunsuke Igarashi, Shiho Torashima, and Masahiro Yamaguchi [Non-Patent Document 5] S. Maekawa, K. Nitta, and O. Matoba, “Transmissive optical imaging device with micromirror array,” Proc. SPIE 6392, 63920E (2006) Summary of the Invention [Problem to be solved by the invention]

[0010] In view of the above-mentioned conventional circumstances, an object of the present invention is to realize a spatial image display device that allows the background to be observed (see-through).

[0011] In view of the above-described conventional situation, the object of the present invention is to prevent degradation of display performance, such as a decrease in contrast due to light scattering caused by the structure of the imaging element, or the generation of virtual images, in a spatial image display device in which the background can be observed and the optical path between the display screen, which is the projection object, and its image has an imaging optical path that is symmetrical with respect to the imaging element surface.

[0012] Another object of the present invention is to prevent a reduction in the freedom of structural design due to the imaging conditions of the imaging element in a spatial image display device in which the background can be observed, and in which the optical path between the display screen, which is the projection object, and its image has an imaging optical path that is symmetrical with respect to the imaging element surface.

[0013] Furthermore, an object of the present invention is to display a real image while correcting for wavelength dispersion in a spatial image display device in which the background can be observed, and in which the optical path between the display screen, which is the projection object, and its image has an imaging optical path that is symmetrical with respect to the imaging element surface.

[0014] Other objects of the present invention and specific advantages obtained by the present invention will become more apparent from the following description of the embodiments. [Means for solving the problem]

[0015] In this invention, by placing two equivalent holographic diffraction elements (HOE: Holographic Optical Elements) in symmetrical positions with respect to the plane of an imaging element such as a dihedral corner reflector array (DCRA) in the imaging optical path, it is possible to observe the background of the spatial image while preventing degradation of display performance such as a decrease in contrast due to light scattering caused by the structure of the imaging element, a decrease in resolution due to wavelength dispersion of the HOE, and the generation of virtual images.

[0016] That is, the present invention is directed to a display device screen that is a projection object. A spatial image, which is an aerial projection image of the display device screen The optical path between An imaging element that forms an image of a point light source at a plane-symmetric position A method for displaying a spatial image in a spatial image display device having an imaging optical path symmetrical with respect to an imaging element surface, comprising: At a position symmetrical to A first wavelength dispersive element and a second wavelength dispersive element that generate equivalent wavelength dispersion and projecting a spatial image, which is an aerial projection image of the display device screen, which is the projection object, through an imaging optical path that is plane-symmetric with respect to the imaging element plane, which is constituted by an imaging element that forms an image of the point light source at a plane-symmetric position, a first wavelength dispersion element, and a second wavelength dispersion element. It is characterized by displaying

[0017] In the aerial image display method according to the present invention, at least one of the first wavelength dispersion element and the second wavelength dispersion element is A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The optical element may be configured to transmit some or all of the light rays other than the light rays that form an image.

[0018] The aerial image display method according to the present invention comprises: A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The observer can observe the background through the light beam transmitted through the second wavelength dispersive element from behind.

[0019] Furthermore, the aerial image display method according to the present invention can display an aerial image by using holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

[0020] Furthermore, the aerial image display method according to the present invention can display an aerial image by using a reflective holographic diffraction element as the first wavelength dispersive element and the second wavelength dispersive element.

[0021] Furthermore, the aerial image display method according to the present invention can display an aerial image using transmission holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

[0022] The spatial image display method according to the present invention is also An imaging element that forms an image of a point light source at a plane-symmetric position Using a two-plane orthogonal corner reflector array as A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The image may be formed by:

[0023] In the aerial image display method according to the present invention, the two-plane orthogonal corner reflector array The single-reflection light path incident on each of the two orthogonal corner reflectors that make up the may be oriented away from the observer.

[0024] Furthermore, in the spatial image display method according to the present invention, the hologram diffraction element used as the second wavelength dispersion element may have a virtual image optical path that does not satisfy the diffraction condition.

[0025] Furthermore, the wavelength dispersion correcting method according to the present invention is characterized in that in the above-described aerial image displaying method, wavelength dispersion is corrected using an imaging element that forms a point image at a plane-symmetric position of the point light source object.

[0026] The present invention provides An imaging element that forms an image of a light source at a plane-symmetric position A spatial image display device having an imaging optical path symmetrical with respect to an imaging element surface, In contrast to A first wavelength dispersion element and a second wavelength dispersion element are arranged at symmetrical positions to generate equal wavelength dispersion. and projecting and displaying a spatial image, which is an aerial projection image of a display device screen, which is the projection object, via an imaging optical path that is plane-symmetric with respect to the imaging element plane, which is configured by an imaging element that forms an image of the point light source at a plane-symmetric position, and a first wavelength dispersion element and a second wavelength dispersion element that generate equivalent wavelength dispersion and are arranged at plane-symmetric positions with respect to the imaging element plane of the imaging element. It is characterized by:

[0027] In the spatial image display device according to the present invention, at least one of the first wavelength dispersion element and the second wavelength dispersion element is A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The optical element may be configured to transmit some or all of the light rays other than the light rays that form an image.

[0028] The spatial image display device according to the present invention can also include two holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

[0029] The spatial image display device according to the present invention comprises: A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The observer can observe the background through the light beam transmitted through the second wavelength dispersive element from behind.

[0030] In the spatial image display device according to the present invention, the two holographic diffraction elements can be reflective holographic diffraction elements.

[0031] In the spatial image display device according to the present invention, the two holographic diffraction elements can be transmission type holographic diffraction elements.

[0032] In addition, in the spatial image display device according to the present invention, The image of a point light source is formed at a plane-symmetric position The imaging element may be a two-sided orthogonal corner reflector array.

[0033] In the spatial image display device according to the present invention, the two-plane orthogonal corner reflector array The single-reflection light path incident on each of the two orthogonal corner reflectors that make up the may be oriented away from the observer.

[0034] Furthermore, the spatial image display device according to the present invention may have a virtual image optical path that does not satisfy the diffraction condition in the hologram diffraction element used as the second wavelength dispersion element.

[0035] Furthermore, the wavelength dispersion correcting device according to the present invention is characterized in that in the above aerial image display device, wavelength dispersion is corrected by an imaging element that forms a point image at a plane-symmetric position of the point light source object. [Effects of the Invention]

[0036] In the present invention, the projection object is a display screen and A spatial image, which is an aerial projection image of the display device screen The optical path between An imaging element that forms an image of a point light source at a plane-symmetric position In a spatial image display device having an imaging optical path symmetrical with respect to an imaging element surface, At a position symmetrical to A first wavelength dispersive element and a second wavelength dispersive element that generate equivalent wavelength dispersion and projecting a spatial image, which is an aerial projection image of the display device screen, which is the projection object, through an imaging optical path that is plane-symmetric with respect to the imaging element plane, which is constituted by an imaging element that forms an image of the point light source at a plane-symmetric position, a first wavelength dispersion element, and a second wavelength dispersion element. By displaying the image, it is possible to observe the spatial image, while preventing degradation of display performance such as a decrease in contrast due to light scattering caused by the structure of the imaging element, a decrease in resolution due to wavelength dispersion of the HOE, and the generation of virtual images.It also prevents a decrease in the freedom of structural design due to the imaging conditions of the imaging element.

[0037] In addition, in the present invention, in a spatial image display device having an imaging optical path in which an optical path between a display screen as a projection object and an image thereof is symmetrical with respect to an imaging element surface, at least one of the first wavelength dispersion element and the second wavelength dispersion element is Aerial image, which is an aerial projection image of the display screen, which is the projection object By making the lens transmit some or all of the light rays other than the light rays that form the image, it is possible to observe the background object. can.

[0038] Although an aerial image that allows observation of background objects can be formed even if the first wavelength dispersion element and the second wavelength dispersion element, which are components of the present invention, are replaced with half mirrors, the present invention can form an aerial image with higher contrast than this.

[0039] Furthermore, the first wavelength dispersion element and the second wavelength dispersion element, which are components of the present invention, are arranged at symmetrical positions on the imaging element plane and generate wavelength dispersions equal to each other, making it possible to correct wavelength dispersion.

[0040] Furthermore, in the present invention, wavelength dispersion can be corrected by forming a point image at a plane-symmetric position of the point light source object using an imaging element, and virtual images can be reduced, allowing the aerial image to be displayed as a real image. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a side view showing the configuration of a spatial image display device according to one embodiment of the present invention. [Figure 2] Figure 2 shows the optical path of the spatial image display device, where (A) is a top view showing the optical path below the imaging element surface of the spatial image display device, and (B) is a top view showing the optical path above the imaging element surface of the spatial image display device. [Figure 3]Figure 3 shows images obtained by placing an observation camera at the position of the user's eye shown in Figure 1 in the above-mentioned spatial image display device and adjusting the focus of the observation camera, where (A) in Figure 3 is an image obtained by adjusting the focus to the aerial projection image, (B) in Figure 3 is an image obtained by adjusting the focus to the intermediate second wavelength dispersion element, and (C) in Figure 3 is an image obtained by adjusting the focus to the background. [Figure 4] Figure 4 is a top view illustrating a virtual image formed by light wavelength-dispersed by the first wavelength dispersion element in the spatial image display device, where (A) in Figure 4 shows the optical path when the Bragg angle ΘB condition is 45°≫ΘB≧θu, (B) in Figure 4 shows the optical path when the Bragg angle ΘB condition is 45°≒ΘB=θu, and (C) in Figure 4 shows the optical path when the Bragg angle ΘB condition is 45°≪ΘB~θu. [Figure 5] Figure 5 is a diagram explaining the virtual image in the spatial image display device, where (A) in Figure 5 is a characteristic diagram showing the dependency of the virtual image brightness of the imaging element on the horizontal incident angle, (B) in Figure 5 is a characteristic diagram showing the dependency of the diffraction efficiency according to the HOE coupled wave theory on the incident angle, and (C) in Figure 5 is a characteristic diagram showing the dependency of the effective virtual image brightness on the incident angle θ. [Figure 6] Figure 6 is a diagram for explaining the correction of blurring of the aerial image formed in the above-mentioned aerial image display device, where (A) in Figure 6 is an image obtained by capturing the aerial image formed in the above-mentioned aerial image display device, and (B) in Figure 6 shows an image obtained by capturing the aerial image formed in the comparative reference light path with the second wavelength dispersion element replaced with a normal total reflection mirror. [Figure 7] FIG. 7 is a diagram showing a comparative reference optical path in which the second wavelength dispersion element is replaced with a normal total reflection mirror. [Figure 8]Figure 8 is a diagram for explaining the correction of a virtual image of an aerial image formed in the above-mentioned aerial image display device, where (A) of Figure 8 shows a comparative reference optical path in which the first wavelength dispersion element 12 and the second wavelength dispersion element 14 in the above-mentioned aerial image display device 10 are replaced with ordinary total reflection mirrors 22 and 24, and (B) of Figure 8 shows an image obtained by capturing the aerial image with a virtual image together with the real image formed by the above-mentioned comparative reference optical path. [Figure 9] Figure 9 is a diagram used to explain the correction of a virtual image of an aerial image formed in the above-mentioned aerial image display device, where (A) in Figure 9 is an image obtained by capturing a clear aerial image without a virtual image in which blurring in the diffraction direction of the aerial image has been corrected, and (B) in Figure 9 is an image obtained by magnifying the aerial image by 100 times. [Figure 10] FIG. 10 is a side view showing the configuration of a spatial image display device using transmission holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element. [Figure 11] Figure 11 is a diagram showing the optical path of the spatial image display device, where (A) of Figure 11 is a top view showing the optical path below the imaging element surface of the spatial image display device, and (B) of Figure 11 is a top view showing the optical path above the imaging element surface of the spatial image display device. DETAILED DESCRIPTION OF THE INVENTION

[0042] A preferred embodiment of the present invention will be described in detail below. Note that the embodiment described below does not unduly limit the content of the present invention as defined in the claims, and not all of the configurations described in the embodiment are necessarily essential as means for solving the problems of the present invention.

[0043] Figure 1 is a side view showing the configuration of a spatial image display device 10 according to one embodiment of the present invention, and Figure 2 is a diagram showing the optical path of this spatial image display device 10, with (A) of Figure 2 being a top view showing the optical path below the imaging element surface 13A of the spatial image display device 10, and (B) of Figure 2 being a top view showing the optical path above the imaging element surface 13A of the spatial image display device 10.

[0044] This spatial image display device 10 is an aerial image display device having an imaging optical path in which the optical path between the projection object, a display screen 11A, and its image is symmetrical with respect to an imaging element surface 13A, and is equipped with a first wavelength dispersion element 12 and a second wavelength dispersion element 14 that generate equivalent wavelength dispersion and are arranged at symmetrical positions with respect to the imaging element surface 13A, and displays an aerial image 15 via the first wavelength dispersion element 12 and the second wavelength dispersion element 14.

[0045] The aerial image display device 10 uses an imaging element 13 called a micro-mirror array plate (MMAPs), a transmissive mirror device (TMD), a dihedral corner reflector array (DCRA), a Parity Mirror (trademark), or an aerial imaging plate (AI) plate, which forms an image of a point light source at a plane-symmetric position, to project an image onto a flat panel display (FPD) such as a liquid crystal display (LCD), an organic light emitting diode (OLED), an LED display, or a quantum dot light emitting diode (QLED). The present invention is applied to an optical system that projects an aerial image such as a display (FPD) or a display image projected by a projector or laser projector, and the display screen 11A, which is the projection object (display image such as an FPD), and the aerial projected image, that is, the aerial image 15, are positioned symmetrically with respect to the imaging element surface 13A, and the optical path between the display screen 11A and the aerial image 15 has an imaging optical path that is symmetric with respect to the imaging element surface 13A.

[0046] In this aerial image display device 10, the first wavelength dispersion element 12 and the second wavelength dispersion element 14, which generate the equivalent wavelength dispersion, are disposed in symmetrical positions with respect to the imaging element surface 13A in the symmetrical imaging optical path. These elements are equivalent holographic mirrors (holographic diffraction elements (HOEs)), prisms, diffractive optical elements, or other transparent reflective, diffractive, or refracting devices, respectively. This allows the image on the imaging element surface 13A to be projected onto the imaging position and form an aerial image 15. By employing transparent reflective, diffractive, or refracting devices as the first wavelength dispersion element 12 and the second wavelength dispersion element 14, an observer peering through the aerial image can observe the background through the aerial image. In other words, an observer of the aerial image 15 can observe the background from behind using light passing through the second wavelength dispersion element 14. While a similar effect can be achieved by using a half mirror or a polarizing beam splitter instead of these wavelength dispersion elements, the aerial image quality cannot be as good as that of the present invention.

[0047] FIG. 3 shows an image IM obtained in the spatial image display device 10 by placing an observation camera at the position of the user's eye shown in FIG. 1 and adjusting the focus of the observation camera in order of depth. A ,IM B ,IM C 3A shows an image IM obtained by adjusting the focus to the aerial projection image. A 3B shows an image IM obtained by adjusting the focus to the intermediate second wavelength dispersion element 14. B 3C shows an image IM obtained by focusing on the background image 16. C is.

[0048] By focusing the observation camera on the aerial image 15, the image IM shown in FIG. A As shown in FIG. 3C, the background image 16 becomes blurred and a clear aerial image 15 is obtained. By focusing the observation camera on the background, the image IM CAs shown in FIG. 3B, the aerial image 15 becomes blurred and a clear background image 16 is obtained. By focusing the observation camera on the second wavelength dispersion element 14, the image IM shown in FIG. B As shown in FIG. 3A, a blurred aerial image 15 and a blurred background image 16 are obtained, and in the aerial image display device 10, the image IM shown in FIG. 3A is generated due to the difference in the focal position. A It can be seen that the aerial image 15 is formed as an aerial projection image, and the image IM shown in FIG. C It was confirmed that the background image 16 can be observed.

[0049] Here, the area surrounded by the dashed ellipse in FIG. 1 indicates the retro-reflection area of ​​the imaging element 13, and the areas surrounded by the dashed-dotted ellipse in FIGS. 1 and 2(A) and (B) indicate the diffraction areas of the first wavelength dispersion element 12 and the second wavelength dispersion element 14.

[0050] In this aerial image display device 10, wavelength dispersion occurs in the first wavelength dispersion element 12 during optical path propagation due to Bragg diffraction or the like, as shown in Fig. 2(A), but this is corrected by back-propagating diffraction to the second wavelength dispersion element 14 along a symmetrical optical path, as shown in Fig. 2(B). Furthermore, because the optical path of the virtual image is not symmetrical, there exists an optical path that does not satisfy the Bragg condition in the second wavelength dispersion element 14, which can reduce the virtual image. Furthermore, the virtual image can be suppressed by limiting the angle of the diffraction condition of the first wavelength dispersion element 12.

[0051] 4A and 4B are diagrams for explaining a virtual image formed by the light wavelength-dispersed by the first wavelength dispersion element 12 in the spatial image display device 10. FIG. 4A shows the Bragg angle Θ B Condition is 45°≫Θ B ≧θ u The optical path in this case is shown in Fig. 4(B), and the Bragg angle Θ B The condition is 45°≒Θ B =θ u The optical path in this case is shown in Fig. 4(C), and the Bragg angle Θ B Condition is 45°≪Θ B ~θ uThe optical path in this case is shown.

[0052] That is, in this spatial image display device 10, the light (virtual image light) wavelength-dispersed by the first wavelength dispersion element 12 is reflected by the Bragg angle Θ B Condition is 45°≫Θ B ≧θ u In this case, the virtual image light is transmitted through the second wavelength dispersion element 14 and is not directed toward the user, but the Bragg angle Θ B The condition is 45°≒Θ B =θ u In the case of , the brightness of the virtual image increases around that point, and the Bragg angle θ B Condition is 45°≪Θ B ~θ u In this case, the Bragg condition is not satisfied by the second wavelength dispersive element 14, and no transmitted virtual image is observed.

[0053] Figure 5 is a diagram explaining the virtual image in the spatial image display device 10, where (A) in Figure 5 is a characteristic diagram showing the dependency of the virtual image brightness of the imaging element 13 on the horizontal incident angle, (B) in Figure 5 is a characteristic diagram showing the dependency of the diffraction efficiency according to the HOE coupled wave theory on the incident angle, and (C) in Figure 5 is the dependency of the effective virtual image brightness on the incident angle θ.

[0054] In FIG. 5A, the dependency of the virtual image brightness of the imaging element 13 of the spatial image display device 10 on the horizontal incident angle θ is shown as the reflectance characteristic of one reflection (solid line) and the reflectance characteristic of two reflections (dashed line). B Condition is 45°≫Θ B ≧θ u In this case, the virtual image brightness is in the range A1, and the Bragg angle θ B The condition is 45°≒Θ B =θ u In this case, the virtual image brightness is in the range A2, and by multiplying this by the dependency of the diffraction efficiency on the incident angle θ according to the HOE coupled-wave theory shown in Figure 5(B), the dependency of the effective virtual image brightness on the incident angle θ is shown as Figure 5(C).

[0055] In FIG. 5C, the luminance characteristic F1 (dashed line) of imaging element 13 and the luminance characteristic F2 (chain line) according to coupled wave theory are multiplied by the luminance characteristic F1 and the luminance characteristic F2 to form an effective virtual image luminance characteristic F3, which is shown by a solid line. [Example]

[0056] As the imaging element 13, which forms an image of a point light source at a plane-symmetric position, a 100 mm square dihedral corner reflector array (DCRA) [see Non-Patent Document 5] manufactured by Parity Innovations Inc. (Kyoto Prefecture) was used. An ASK3D plate manufactured by Asukanet Co., Ltd. can also be used.

[0057] A dihedral corner reflector array (DCRA) is an optical element in which square through-holes are formed in an array on a substrate, with the inner walls of the through-holes acting as mirrors. Light rays incident from below the substrate are reflected twice by the inner walls of each through-hole, generating an image at a symmetrical position above.

[0058] The object to be projected was a general transmission screen, and an image was projected onto the display device screen 11A by a projector. The optical path was the same as that of the aerial image display device 10 shown in Figures 1 and 2(A) and (B).

[0059] The first wavelength dispersive element 12 and the second wavelength dispersive element 14 were holographic diffraction elements (HOEs) made of photopolymer manufactured by Covestro AG (Leverkusen, Germany) and exposed by the method described below.

[0060] The holographic diffraction element (HOE) was fabricated using the exposure optical system described in the non-patent document [4]. The light source was a single-frequency transverse mode TEM with red, green, and blue wavelengths. 00The laser beams were split into two beams using a half-wave plate and a polarizing beam splitter, then combined into three beams each using a dichroic prism. The beams were then introduced into a single-mode fiber and guided to the desired location. The laser beams emitted from the fiber were then passed through spatial filters and collimated to the desired parallel beam size, one serving as the object beam and the other as the reference beam. In this example, the beam diameter was 0.7 mm. The laser beam was modulated by an acousto-optic modulator before entering the fiber, and the dose to the photopolymer was controlled by pulse width modulation (PWM). The exposure optical path was configured so that two beams overlapped on the photopolymer film at angles of 0° (normal incidence) and 135°, allowing sequential exposure for each wavelength. After exposure, the photopolymer was stabilized by 10 minutes of UV irradiation. In this way, a holographic mirror (holographic diffraction element (HOE)) was fabricated, which diffracts normal incident light at an angle of 45° or vice versa.

[0061] Since the display image, which is the projection object, requires a high contrast image, we used a DLP type data projector manufactured by Plus Corporation, projecting an image onto a transmissive diffuser.

[0062] The images taken from the rear of the optical path are shown in Figure 3 (A), (B), and (C). Figure 3 (A) is an image IM focused on the aerial image (the letters TOKYO TECH) 15. A 3B shows an image IM focused on the second wavelength dispersion element 14. B ,(C) of Figure 3 shows an image IM focused on the background object (Tokyo Institute of Technology Ookayama Campus Main Building) 16. C is.

[0063] As described above, in the aerial image display device 10, wavelength dispersion occurs due to Bragg diffraction or the like in the first wavelength dispersion element 12 during optical propagation, but this is corrected by back-propagating diffraction to the second wavelength dispersion element 14 along a symmetrical optical path. Furthermore, since the optical path of the virtual image is not symmetrical, there exists an optical path that does not satisfy the Bragg condition in the second wavelength dispersion element 14, which can reduce the virtual image. Furthermore, by limiting the angle of the diffraction condition of the first wavelength dispersion element 12, virtual images can also be suppressed.

[0064] FIG. 6 is a diagram illustrating the correction of blur of the aerial image formed in the aerial image display device 10. FIG. 6(A) shows an image IM obtained by capturing the aerial image formed in the aerial image display device. D 6B shows an image IM obtained by capturing an aerial image formed in a comparative reference optical path in which the second wavelength dispersion element 14 is replaced with a normal total reflection mirror 24. E is.

[0065] That is, in the comparative reference optical path shown in FIG. 7 in which the second wavelength dispersion element 14 in the aerial image display device 10 in which the aerial image as shown in FIG. 6A is formed is replaced with a normal total reflection mirror 24, blurring in the diffraction direction in the first wavelength dispersion element 12 is not corrected by back-propagation diffraction to the second wavelength dispersion element 14, and therefore a blurred aerial image as shown in FIG. 6B is formed.

[0066] 8A and 8B are diagrams for explaining correction of a virtual image of an aerial image formed in the aerial image display device 10. FIG. 8A shows a comparative reference optical path in which the first wavelength dispersion element 12 and the second wavelength dispersion element 14 in the aerial image display device 10 are replaced with normal total reflection mirrors 22 and 24. FIG. 8B shows an image IM obtained by capturing an aerial image by using the virtual image together with the real image formed by this comparative reference optical path. F This shows:

[0067] That is, in the comparative reference optical path shown in FIG. 8A in which the first wavelength dispersion element 12 and the second wavelength dispersion element 14 in the aerial image display device 10 are replaced with normal total reflection mirrors 10 and 24, the image IM shown in FIG. 8B isF As shown above, a virtual image is formed along with a real image as a spatial image.

[0068] In contrast to this, FIG. 9 is a diagram for explaining the suppression of a virtual image formed in the aerial image display device 10. FIG. 9(A) shows an image IM obtained by capturing a clear aerial image in which blurring in the diffraction direction of the aerial image has been corrected and which is free from a virtual image. G , and (B) in Figure 9 is an image IM obtained by magnifying the aerial image by 100 times. H is.

[0069] That is, in the spatial image display device 10 equipped with the first wavelength dispersion element 12 and the second wavelength dispersion element 14, the image IM shown in FIG. 9(A) is G As shown in Fig. 9B, the image IM shown in Fig. 9B was obtained by magnifying the aerial image in Fig. 9A by 100 times. H Even in this case, the virtual image cannot be confirmed. [Example]

[0070] In the first embodiment, the spatial image display device 10 is configured using transmission holographic diffraction elements as the first wavelength dispersion element 12 and the second wavelength dispersion element 14. However, as shown in FIGS. 10 and 11(A) and (B), the same effect can be achieved by using transmission holographic diffraction elements as the first wavelength dispersion element 12 and the second wavelength dispersion element 14.

[0071] In this Example 2, the components used are the same as those in Example 1, except for the diffraction directions of the first wavelength dispersion element 12 and the second wavelength dispersion element 14. Furthermore, the exposure method for the first wavelength dispersion element 12 and the second wavelength dispersion element 14 used in this Example 2 is the same as that in Example 1, except that the incident angle of the light beam incident at 135° in Example 1 is changed to 45°.

[0072] In this second embodiment, the same effects as those in the first embodiment can be obtained.

[0073] The first and second embodiments given here are merely examples of the present invention, and the type of imaging element, the element that generates wavelength dispersion, and the display that is the projection object are not limited to these.

[0074] As shown in Figures 1 and 10, the spatial image display devices 10 and 20 to which the present invention is applied are spatial image display devices having an imaging optical path that is symmetrical with respect to the imaging element surface 13A, and are equipped with first wavelength dispersion elements 12 and 12A and second wavelength dispersion elements 14 and 14A that generate equivalent wavelength dispersion and are arranged at symmetrical positions with respect to the imaging element surface 13A.

[0075] The aerial image display method according to the present invention is carried out by the aerial image display devices 10 and 20 described above.

[0076] That is, the aerial image display devices 10 and 20 have a display screen 11A as a projection object and A spatial image, which is an aerial projection image of the display device screen 11A The optical path between An imaging element that forms an image of a point light source at a plane-symmetric position A spatial image display device having an imaging optical path symmetrical with respect to an imaging element surface 13A, Plane-symmetric with respect to First wavelength dispersion elements 12, 12A and second wavelength dispersion elements 14, 14A are arranged at positions An aerial projection image of the display device screen, which is the projection object, is projected through an imaging optical path that is plane-symmetrical with respect to the imaging element surface. A spatial image 15 is displayed.

[0077] At least one of the first wavelength dispersion element 12, 12A and the second wavelength dispersion element 14, 14A in the spatial image display device 10, 20 is A spatial image, which is an aerial projection image on the display device screen, which is the projection object. In the spatial image display method according to the present invention, at least one of the first wavelength dispersion element 12, 12A and the second wavelength dispersion element 14, 14A may be configured to transmit a part or all of the light rays other than the light rays that form an image. A spatial image, which is an aerial projection image on the display device screen, which is the projection object. The spatial image display method according to the present invention can transmit a part or all of the light rays other than the light rays that form an image of the object, and the spatial image display method can transmit the light rays through the first wavelength dispersion element 12, 12A and the second wavelength dispersion element 14, 14A that use a hologram diffraction element. The aerial projection image on the display device screen, which is the projection object, is The aerial image 15 can be displayed. The aerial image display method according to the present invention includes the following steps: The aerial projection image on the display device screen, which is the projection object, isA viewer of the aerial image 15 can observe the background from behind by light rays passing through the second wavelength dispersive element 14, 14A.

[0078] Furthermore, the aerial image display devices 10, 20 can be provided with two hologram diffraction elements as the first wavelength dispersion element 12, 12A and the second wavelength dispersion element 14, 14A, and the aerial image display method according to the present invention can display the aerial image 15 via the first wavelength dispersion element 12, 12A and the second wavelength dispersion element 14, 14A using hologram diffraction elements.

[0079] Furthermore, as in the aerial image display device 10, the two hologram diffraction elements can be reflective hologram diffraction elements, and the aerial image display method of the present invention can display the aerial image 15 via a first wavelength dispersion element 12 and a second wavelength dispersion element 14 that use reflective hologram diffraction elements as the hologram diffraction elements. Furthermore, as in the aerial image display device 20, the two hologram diffraction elements can be transmission type hologram diffraction elements, and the aerial image display method according to the present invention can display the aerial image 15 via a first wavelength dispersion element 12A and a second wavelength dispersion element 14A that use transmission type hologram diffraction elements as the hologram diffraction elements.

[0080] Furthermore, the imaging element 13 in the aerial image display devices 10 and 20 can be a two-plane orthogonal corner reflector array, and the aerial image display method according to the present invention can be The image of a point light source is formed at a plane-symmetric position A two-sided orthogonal corner reflector array is used as the imaging element 13. The aerial projection image on the display device screen, which is the projection object, is An aerial image 15 can be formed.

[0081] In the spatial image display devices 10 and 20, the imaging element 13 Two-sided orthogonal corner reflector array used as The single-reflection light path incident on each of the two orthogonal corner reflectors that make up thecan be directed in a direction opposite to the viewer, and in the spatial image display method according to the present invention, the imaging element 13 using the above-mentioned two-plane orthogonal corner reflector array can be The single-reflection light path incident on each of the two-surface orthogonal corner reflectors that make up the two-surface orthogonal corner reflector array may be oriented away from the observer.

[0082] Furthermore, the spatial image display device 10 can have a virtual image optical path that does not satisfy the diffraction condition with the hologram diffraction element used as the second wavelength dispersion element 14, and the spatial image display method according to the present invention can have a virtual image optical path that does not satisfy the diffraction condition with the second wavelength dispersion element 14 using the hologram diffraction element.

[0083] Furthermore, the aerial image display devices 10 and 20 can be configured to correct chromatic dispersion using an imaging element 13 that forms a point image at a plane-symmetrical position relative to the point-light-source object, thereby reducing virtual images and displaying the aerial image as a real image. That is, in the aerial image display devices 10 and 20, a chromatic dispersion correction device can be configured that corrects chromatic dispersion using an imaging element 13 that forms a point image at a plane-symmetrical position relative to the point-light-source object. Therefore, in the aerial image display devices 10 and 20, the chromatic dispersion correction method in the aerial image display method according to the present invention can be implemented by correcting chromatic dispersion using an imaging element 13 that forms a point image at a plane-symmetrical position relative to the point-light-source object.

[0084] The present invention not only provides a spatial image in which the background can be observed, but can also be used to correct any chromatic dispersion in an optical path or optical device that generates chromatic dispersion. [Explanation of symbols]

[0085] 10, 20 aerial image display device, 11A display screen, 12, 12A first wavelength dispersive element, 13 imaging element, 13A imaging element surface, 14, 14A second wavelength dispersive element, 15 aerial image, 15' virtual image, 16 background image, 22, 24 total reflection mirror,

Claims

1. 1. A method for displaying an aerial image in an aerial image display device, in which an optical path between a display device screen, which is a projection object, and an aerial image, which is an aerial projection image of the display device screen, is symmetrical with respect to an imaging element plane of an imaging element that forms an image of a point light source at a plane-symmetric position, a first wavelength dispersion element and a second wavelength dispersion element that generate equivalent wavelength dispersion are disposed at positions that are plane-symmetric with respect to the imaging element plane; A spatial image display method in which an aerial image, which is an aerial projection image of the projection object, a display device screen, is projected and displayed via an imaging optical path that is plane-symmetric with respect to the imaging element surface and is composed of an imaging element that forms an image of the point light source at a plane-symmetric position, a first wavelength dispersion element, and a second wavelength dispersion element.

2. 2. The aerial image display method according to claim 1, wherein at least one of the first wavelength dispersion element and the second wavelength dispersion element transmits some or all of the light rays other than the light rays that form the aerial image, which is an aerial projection image on the display screen, which is the projection object.

3. The spatial image display method according to claim 1 or claim 2, wherein an observer of the spatial image, which is an aerial projection image on the display device screen, which is the projection object, can observe the background from behind by a light ray passing through the second wavelength dispersion element.

4. 4. The method for displaying an aerial image according to claim 1, wherein the aerial image is displayed using holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

5. 5. The method for displaying an aerial image according to claim 4, wherein the aerial image is displayed using reflection type holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

6. 5. The method for displaying an aerial image according to claim 4, wherein the aerial image is displayed using transmission holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

7. A method for displaying an aerial image as described in any one of claims 1 to 6, characterized in that a two-sided orthogonal corner reflector array is used as an imaging element that forms an image of the point light source at a plane-symmetric position, thereby forming an aerial image that is an aerial projection image of the display device screen that is the projection object.

8. 8. The method for displaying a spatial image according to claim 7, wherein the single-reflection light path incident on each of the two-surface orthogonal corner reflectors constituting the two-surface orthogonal corner reflector array is directed in a direction away from the viewer.

9. 5. The method for displaying a spatial image according to claim 4, wherein the hologram diffraction element used as the second wavelength dispersion element has a virtual image optical path that does not satisfy the diffraction condition.

10. 10. The method for correcting wavelength dispersion in a spatial image display method according to claim 1, wherein wavelength dispersion is corrected using an imaging element that forms a point image at a plane-symmetric position of a point light source object.

11. An aerial image display device having an imaging optical path in which an optical path between a display device screen, which is a projection object, and an aerial image, which is an aerial projection image of the display device screen, is symmetrical with respect to an imaging element plane of an imaging element that forms an image of a point light source at a plane-symmetric position, a first wavelength dispersion element and a second wavelength dispersion element that are arranged at positions symmetrical with respect to the imaging element plane and generate equivalent wavelength dispersion; A spatial image display device that projects and displays a spatial image, which is an aerial projection image of the display screen, which is the projection object, via an imaging optical path that is plane-symmetrical with respect to the imaging element surface, and is composed of an imaging element that focuses the image of the point light source at a plane-symmetrical position, and a first wavelength dispersion element and a second wavelength dispersion element that generate equivalent wavelength dispersion and are arranged at plane-symmetrical positions with respect to the imaging element surface of the imaging element.

12. 12. The spatial image display device according to claim 11, wherein at least one of the first wavelength dispersion element and the second wavelength dispersion element transmits some or all of the light rays other than the light rays that form the spatial image, which is the aerial projection image on the display screen, which is the projection object.

13. A spatial image display device as described in claim 11 or claim 12, wherein an observer of the spatial image, which is an aerial projection image of the display screen, which is the projection object, can observe the background from behind by light rays passing through the second wavelength dispersion element.

14. 14. The spatial image display device according to claim 11, further comprising two holographic diffraction elements as the first wavelength dispersive element and the second wavelength dispersive element.

15. 15. The spatial image display device according to claim 14, wherein the two holographic diffraction elements are reflective holographic diffraction elements.

16. 15. The spatial image display device according to claim 14, wherein the two holographic diffraction elements are transmission type holographic diffraction elements.

17. 17. The spatial image display device according to claim 11, wherein the imaging element for forming the image of the point light source at a plane-symmetric position is a two-plane orthogonal corner reflector array.

18. 18. The spatial image display device according to claim 17, wherein a single-reflection light path incident on each of the two-surface orthogonal corner reflectors constituting the two-surface orthogonal corner reflector array is directed in a direction away from the viewer.

19. 15. The spatial image display device according to claim 14, wherein the hologram diffraction element used as the second wavelength dispersion element has a virtual image optical path that does not satisfy the diffraction condition.

20. 20. The wavelength dispersion correcting device for a spatial image display device according to claim 11, wherein wavelength dispersion is corrected by the imaging element that forms a point image at a plane-symmetric position of a point light source object.

Images