Image projection device

Abstract

To provide an image display device that can improve its power of expression when forming virtual images at a plurality of positions in a depth direction.SOLUTION: An image projection device (100) comprises: a cut image acquisition unit (10) that acquires a plurality of cut surface images (D1-D4) at different depth positions from a virtual three-dimensional shape; a plurality of image display units (20) that respectively display the plurality of cut surface images; and an image forming optical unit (30) that radiates the plurality of cut surface images (D1-D4) displayed by the plurality of image display units (20) as a plurality of rays of image light, and forms the plurality of rays of image light into images at different distances from a viewpoint.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an image projection device, and more particularly to an image projection device that forms an image by superimposing a plurality of images in the depth direction of a space. [Background technology]

[0002] Conventionally, dashboards that illuminate icons have been used to display various types of information inside vehicles. As the amount of information to be displayed increases, it has been proposed to embed an image display device in the dashboard or to configure the entire dashboard with an image display device.

[0003] However, because the instrument panel is located below the windshield of the vehicle, the driver has to move their eyes downward while driving in order to see the information displayed on the instrument panel, which is undesirable. Therefore, a head-up display (hereinafter referred to as HUD) has been proposed, which projects an image onto the windshield so that the driver can read information when looking ahead of the vehicle (see, for example, Patent Document 1). Such a HUD requires an optical device for projecting an image over a wide area of ​​the windshield, and there is a demand for a smaller and lighter optical device.

[0004] Meanwhile, a head-mounted, eyeglass-shaped HUD is known as an image display device that projects light using a small optical device. In a head-mounted HUD, light emitted from a light source is irradiated directly onto the viewer's eyes, projecting an image onto the viewer's retina. Another head-mounted HUD that has been proposed is one that forms multiple images as virtual images at multiple depth positions in the line of sight (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-118669 [Patent Document 2] Patent Publication No. 2021-157117 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with conventional head-mounted HUDs, when images are formed at multiple depth positions simultaneously, virtual images overlap in the line of sight, so the only option is to switch between images and display them individually.As a result, multiple flat images are formed at different depth positions, and the expressiveness is no different from that of a two-dimensional information display.

[0007] Therefore, the present invention has been developed in consideration of the above-mentioned conventional problems, and aims to provide an image display device that can improve the expressive power when virtual images are formed at multiple positions in the depth direction. [Means for solving the problem]

[0008] In order to solve the above problem, the image projection device of the present invention is characterized by comprising a cross-section image acquisition unit that acquires multiple cross-section images at different depth positions from a virtual three-dimensional shape, multiple image display units that display the multiple cross-section images respectively, and an imaging optical unit that irradiates the multiple cross-section images displayed on the multiple image display units as multiple image lights and forms the multiple image lights at different distances from a viewpoint.

[0009] In the image projection device of the present invention, the cross-section image acquisition unit acquires multiple different cross-section images from a virtual three-dimensional shape, and the imaging optical unit images the multiple cross-section images at different distances from the viewpoint, thereby making it possible to improve the expressive power when virtual images are formed at multiple positions in the depth direction.

[0010] In one aspect of the present invention, the imaging optical unit has a display unit that reflects multiple image lights in the direction of the viewpoint, and the multiple image lights are imaged at positions close to and far from the viewpoint from the display unit.

[0011] In one aspect of the present invention, the display unit is a cross beam splitter that reflects the image light from the first direction and the second direction toward the viewing direction.

[0012] In one aspect of the present invention, the multiple image display units include a first imaging unit that irradiates the image light onto the display unit from the first direction and focuses the image light at a position close to the viewpoint, and a second imaging unit that irradiates the image light onto the display unit from the second direction and focuses the image light at a position far from the viewpoint.

[0013] In one aspect of the present invention, the first imaging unit uses a retroreflecting unit to irradiate the image light onto the display unit, and the second imaging unit uses a reflecting mirror to irradiate the image light onto the display unit.

[0014] In one aspect of the present invention, the imaging device further includes a sequential control unit that switches the projection of the plurality of cross-sectional images over time.

[0015] In one aspect of the invention, the sequential control unit switches the plurality of image display units between a display state and a non-display state.

[0016] In one aspect of the present invention, a light-shielding portion that blocks visible light is provided, The sequential control unit changes the position of the light blocking unit to block at least one of the plurality of image lights. [Effects of the Invention]

[0017] The present invention can provide an image display device that can improve the expressive power when virtual images are formed at a plurality of positions in the depth direction. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing an example of the configuration of an image projection device 100 according to a first embodiment. [Figure 2] FIG. 1 is a schematic perspective view showing the configuration of an image projection device 100 according to a first embodiment. [Figure 3] 3A and 3B are schematic diagrams illustrating an example of acquisition of cross-sectional images D1 to D4 by the cross-sectional image acquisition unit 10, where FIG. 3A is a sample image, FIG. 3B is a virtual three-dimensional shape, and FIG. 3C is cross-sectional images D1 to D4 at different depth positions. [Figure 4] 4A and 4B are schematic diagrams illustrating image switching in the sequential control unit 40, where FIG. 4A shows an image when the switching time is increased, and FIG. 4B shows an image when the switching time is decreased. [Figure 5] FIG. 10 is a schematic perspective view showing the configuration of an image projection device 110 according to a second embodiment. [Figure 6] 6A and 6B are schematic diagrams showing an example of the configuration of the sequential control unit 40, in which FIG. 6A explains the virtual images that are selectively displayed, FIG. 6B shows an example of the shading unit 42, and FIG. 6C shows an example of capturing virtual images R1 to R4 from viewpoint E. [Figure 7] 7A and 7B are schematic diagrams showing an example of the configuration of the sequential control unit 40, in which FIG. 7A explains a virtual image that is selectively hidden, FIG. 7B shows an example of a shading unit 42, and FIG. 7C shows an example of capturing virtual images R1 to R4 from viewpoint E. [Figure 8] FIG. 10 is a schematic perspective view showing the configuration of an image projection device 120 according to a third embodiment. [Figure 9] FIG. 10 is a schematic perspective view showing the configuration of an image projection device 130 according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] (First embodiment) Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The same or equivalent components, members, and processes shown in each drawing will be assigned the same reference numerals, and redundant explanations will be omitted where appropriate. FIG. 1 is a block diagram showing an example configuration of an image projection device 100 according to this embodiment. As shown in FIG. 1, the image projection device 100 of this embodiment includes a cross-section image acquisition unit 10, an image display unit 20, an imaging optical unit 30, and a sequential control unit 40.

[0020] In the image projection device 100, each part is controlled using a control unit connected to each part so that information can be communicated therewith. The configuration of the control unit is not limited, but an example includes a CPU (Central Processing Unit) for information processing, a memory device, a recording medium, an information communication device, etc. The control unit controls the operation of each part in accordance with a predetermined program, and sends information including an image (image information) to the image display unit 20.

[0021] The cross-section image acquisition unit 10 is a part that acquires a plurality of cross-section images D1 to D4 at different depth positions from a virtual three-dimensional shape. The cross-section image acquisition unit 10 is a function realized by a program executed by the control unit, and may include hardware such as an imaging device. Acquisition of the cross-section images D1 to D4 by the cross-section image acquisition unit 10 will be described in detail below. Here, an example is shown in which four cross-section images D1 to D4 are used, but the number of images is not limited.

[0022] The image display unit 20 is a part that irradiates image light including the cross-sectional images D1 to D4 acquired by the cross-sectional image acquisition unit 10. The specific configuration of the image display unit 20 is not limited, and a conventionally known display such as a liquid crystal display device or an organic EL display device can be used. As an example, a liquid crystal display device that irradiates light from a light-emitting diode (LED) from the rear side is used. The specific configuration of the image display unit 20 is not limited, and the cross-sectional images D1 to D4 may be displayed on multiple display surfaces, respectively, and in this case, each display surface corresponds to the image display unit 20. Alternatively, the cross-sectional images D1 to D4 may be arranged and displayed in multiple display areas provided on a single display surface, and in this case, each display area corresponds to the image display unit 20.

[0023] The imaging optical unit 30 is a part that irradiates the multiple cross-sectional images D1 to D4 displayed on the image display unit 20 as multiple image lights toward the viewpoint E and forms the cross-sectional images D1 to D4 using the multiple image lights at different distances from the viewpoint E. The specific configuration of the imaging optical unit 30 is not limited, but one example is one that uses multiple beam splitters. An example configuration of the imaging optical unit 30 and the imaging of the cross-sectional images D1 to D4 will be described in detail below.

[0024] The sequential control unit 40 is a unit that switches the projection of the multiple cross-sectional images D1 to D4 over time. The specific configuration of the sequential control unit 40 is not limited, and the sequential control unit 40 may switch between a display state and a non-display state of the multiple cross-sectional images D1 to D4 on the image display unit 20, or may include a light blocking unit 42 that blocks visible light and change the position of the light blocking unit 42 to block at least one of the multiple image lights.

[0025] Fig. 2 is a schematic perspective view showing the configuration of an image projection device 100 according to this embodiment. As shown in Fig. 2, the image projection device 100 includes a plurality of image display units 20, a holding unit ST, beam splitters BS1 to BS4, a mirror M1, and a beam splitter BSM. Furthermore, the plurality of image display units 20 display cross-sectional images D1 to D4, respectively.

[0026] The holder ST is a member that holds the beam splitters BS1 to BS4, the mirror M1, and the beam splitter BSM. The shape and structure of the holder ST are not limited, and it may be in the shape of a glasses frame or a goggle frame. Although the holder ST is shown as a single member in FIG. 2, it may be a combination of multiple members as long as it can maintain the relative positions of the optical elements. The combination of the beam splitters BS1 to BS4, the mirror M1, and the beam splitter BSM corresponds to the imaging optical unit 30 in this invention.

[0027] Beam splitters BS1 to BS4 and beam splitter BSM are optical elements that reflect light incident on one surface and transmit light incident on the other surface. Mirror M1 is an optical element that reflects incident light. Beam splitters BS1 to BS4 are disposed at positions corresponding to cross-sectional images D1 to D4 on image display unit 20, and are inclined at a predetermined angle (for example, 45 degrees) with respect to the traveling direction of image light of cross-sectional images D1 to D4. Mirror M1 is disposed on the path of image light from beam splitters BS1 to BS4, and is inclined at a predetermined angle (for example, 45 degrees) with respect to the traveling direction of image light. Beam splitter BSM is disposed on the path of image light reflected by mirror M1, and is inclined at a predetermined angle (for example, 45 degrees) with respect to the traveling direction of light reflected by mirror M1.

[0028] 2, cross-sectional images D1 to D4 are displayed on the image display unit 20 in order from the side closest to the mirror M1. Furthermore, the beam splitters BS1 to BS4 are also arranged in order from the side closest to the mirror M1. Furthermore, the beam splitters BS1 to BS4, mirror M1, and beam splitter BSM are fixed on a holder ST, and their relative positions and optical axes are fixed.

[0029] The image light of cross-section image D1 displayed on image display unit 20 is reflected by beam splitter BS1, mirror M1, and beam splitter BSM, and reaches viewer's viewpoint E. The image light of cross-section image D2 is reflected by beam splitter BS2, passes through beam splitter BS1, is reflected by mirror M1 and beam splitter BSM, and reaches viewer's viewpoint E. The image light of cross-section image D3 is reflected by beam splitter BS3, passes through beam splitters BS2 and BS1, is reflected by mirror M1 and beam splitter BSM, and reaches viewer's viewpoint E. The image light of cross-section image D4 is reflected by beam splitter BS4, passes through beam splitters BS3, BS2, and BS1, is reflected by mirror M1 and beam splitter BSM, and reaches viewer's viewpoint E.

[0030] As described above, the image light of the cross-sectional images D1 to D4 displayed on the image display unit 20 travels different optical distances before being reflected by the beam splitter BSM. Therefore, the cross-sectional images D1 to D4 are formed as virtual images R1 to R4, respectively, according to the optical distance to the beam splitter BSM. In the example shown in Fig. 2, the cross-sectional images D1 to D4 are formed as virtual images R1 to R4 in order from the position closest to the beam splitter BSM.

[0031] By directing the viewer's line of sight from viewpoint E toward beam splitter BSM, the viewer sees virtual images R1 to R4 formed at different positions in the depth direction. The display contents of virtual images R1 to R4 are cross-sectional images D1 to D4, respectively, which are cross-sectional images at different depth positions of the virtual three-dimensional shape as described above. Therefore, the viewer can see the multiple cross-sectional images D1 to D4 at different positions in the depth direction and see a three-dimensional shape that is close to the original virtual three-dimensional shape. In addition, because beam splitter BSM transmits light incident from the virtual images R1 to R4 side (front), external light from in front of image projection device 100 also reaches viewpoint E, and the virtual images R1 to R4 are displayed superimposed on the external world in front of the viewer's background.

[0032] FIG. 3 is a schematic diagram illustrating an example of acquisition of cross-section images D1 to D4 by the cross-section image acquisition unit 10, where FIG. 3(a) is a sample image, FIG. 3(b) is a virtual three-dimensional shape, and FIG. 3(c) are cross-section images D1 to D4 at different depth positions. First, as shown in FIG. 3(a), the cross-section image acquisition unit 10 acquires a two-dimensional sample image. Next, as shown in FIG. 3(b), the cross-section image acquisition unit 10 acquires a virtual three-dimensional shape from the two-dimensional image using a monocular depth estimation model. Next, as shown in FIG. 3(c), the cross-section image acquisition unit 10 acquires multiple cross-section images D1 to D4 at different depth positions from the virtual three-dimensional shape.

[0033] Here, the cross-sectional images D1 to D4 are two-dimensional images obtained by dividing a virtual three-dimensional shape into a plurality of sections in the depth direction and viewing the sections from a viewpoint E. In the example shown in Fig. 3, the cross-sectional images D1 to D4 correspond to areas cut out from the two-dimensional image shown in Fig. 3(a) corresponding to the sections in the depth direction.

[0034] As shown in Fig. 3(c), the cross-sectional images D1 to D4 acquired by the cross-sectional image acquisition unit 10 are obtained by cutting out the contour of a virtual three-dimensional shape for each section. Therefore, even if virtual images R1 to R4 are simultaneously formed at different positions in the depth direction from the viewpoint E as shown in Fig. 2, overlapping of the display contents in the cross-sectional images D1 to D4 is suppressed. As a result, when a viewer simultaneously views the virtual images R1 to R4 at different depth positions, they can recognize a three-dimensional image that is close to the virtual three-dimensional shape, improving the expressiveness.

[0035] 3(a) to 3(c) show a method of using a monocular depth estimation model from a two-dimensional image, but the method of acquiring data on a virtual three-dimensional shape is not limited, and one example is a known method of presetting a virtual three-dimensional shape using three-dimensional polygon data. In this case, the cross-sectional images D1 to D4 are obtained by dividing the three-dimensional polygon data into multiple sections by slicing them in the depth direction, and projecting each section onto the viewpoint E as a two-dimensional image.

[0036] FIG. 4 is a schematic diagram illustrating image switching by the sequential control unit 40. FIG. 4(a) illustrates an example in which the switching time is increased, and FIG. 4(b) illustrates an example in which the switching time is decreased. As shown in FIGS. 4(a) and 4(b), the sequential control unit 40 sequentially switches between displaying and hiding cross-sectional images D1 to D4 displayed on the image display unit 20. In the example shown in FIGS. 4(a) and 4(b), the sequential switching starts from the cross-sectional image D1 formed by the virtual image R1 at a position close to the viewpoint E, and then switches to the cross-sectional images D2 and D3 formed by the virtual images R2 and R3 in the direction away from the viewpoint E, as indicated by the arrows in the figure. While FIG. 4 illustrates the cross-sectional image D3 formed by the virtual image R3, the sequential switching may also be performed up to the cross-sectional image D4 formed by the virtual image R4. The sequential switching may also be performed from a position far from the viewpoint E to a position close to the viewpoint E, or multiple switching operations may be combined.

[0037] As shown in Figure 4(a), when the switching time between the cross-sectional images D1 to D4 is increased, the display of the virtual images R1 to R4 appears as if individual images are displayed sequentially in the depth direction. This allows the viewer to sequentially recognize slices of a virtual three-dimensional shape, improving the expressiveness when the virtual images R1 to R4 are formed at multiple positions in the depth direction. This type of display can be used to, for example, display a three-dimensional arrow indicating the direction of travel of a vehicle, making the viewer particularly aware of the direction.

[0038] As shown in Figure 4(b), when the switching time between the cross-sectional images D1 to D4 is shortened, the display of the virtual images R1 to R4 appears as if multiple images are displayed continuously in the depth direction due to the persistence of vision effect. This allows the viewer to perceive a three-dimensional image that is close to a virtual three-dimensional shape, improving the expressiveness when the virtual images R1 to R4 are formed at multiple positions in the depth direction. This type of display allows the viewer to become aware of the three-dimensional shape.

[0039] As described above, in the image projection device 100 of this embodiment, the cross-section image acquisition unit 10 acquires multiple different cross-section images D1 to D4 from a virtual three-dimensional shape, and the imaging optical unit 30 forms the multiple cross-section images D1 to D4 at different distances from the viewpoint E, thereby improving the expressive power when virtual images R1 to R4 are formed at multiple positions in the depth direction.

[0040] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to Figs. 5 to 7. Description of content that overlaps with the first embodiment will be omitted. Fig. 5 is a schematic perspective view showing the configuration of an image projection device 110 according to this embodiment. As shown in Fig. 5, the image projection device 110 includes a plurality of image display units 20, a holding unit ST, beam splitters BS1 to BS4, a mirror M1, a beam splitter BSM, and a sequential control unit 40. The sequential control unit 40 also includes a polarizing plate unit 41 and a light blocking unit 42.

[0041] The polarizing plate unit 41 is an optical member that transmits polarized light in a first direction and blocks polarized light in a second direction orthogonal to the first direction. The first direction in which the polarizing plate unit 41 transmits polarized light corresponds to the polarization direction of the image light emitted from the image display unit 20. The light-shielding unit 42 has a transmission region 43a that transmits polarized light in the first direction and a light-shielding region 43b that blocks polarized light in the first direction, and the positions of the transmission region 43a and the light-shielding region 43b are changeable. The transmission region 43a may be a polarizing plate that transmits polarized light in the first direction and blocks polarized light in the second direction, or a light-transmitting plate that transmits visible light. The light-shielding region 43b may be a polarizing plate that blocks polarized light in the first direction and transmits polarized light in the second direction, or a light-shielding plate that blocks visible light.

[0042] Furthermore, the specific configuration of the light-shielding unit 42 is not limited, and a polarizing plate or a light-shielding plate may be moved mechanically, or a polarizing shutter using liquid crystal may be used to move the transmission area 43a. In this embodiment, the image light of the cross-sectional images D1 to D4 displayed on the image display unit 20 is formed as virtual images R1 to R4 when it passes through the transmission area 43a of the light-shielding unit 42. The formation of the virtual images R1 to R4 by the image light of the cross-sectional images D1 to D4 is the same as in the first embodiment.

[0043] 6A to 6C are schematic diagrams showing an example of the configuration of the sequential control unit 40, in which FIG. 6A explains a virtual image that is selectively displayed, FIG. 6B shows an example of the light-shielding unit 42, and FIG. 6C shows an example of capturing virtual images R1 to R4 from viewpoint E. FIGS. 6A to 6C show an example in which the sequential control unit 40 displays only the cross-sectional image D1 and hides the cross-sectional images D2 to D4. As shown in FIG. 6B, in the light-shielding unit 42 of the sequential control unit 40, a transparent region 43a is arranged at a position corresponding to the cross-sectional image D1, and a light-shielding region 43b is arranged at a position corresponding to the cross-sectional images D2 to D4.

[0044] When looking from viewpoint E toward beam splitter BSM, as shown in Fig. 6(c), cross-section image D1 is displayed at the imaging position of virtual image R1, but cross-section images D2 to D4 are not displayed at the imaging positions of virtual images R2 to R4. Therefore, it can be confirmed that virtual image R1 of cross-section image D1 can be selectively formed, as indicated by the diagonal lines in Fig. 6(a). Therefore, by the sequential control unit 40 changing the positions of transmission area 43a and light-blocking area 43b in the light-blocking unit 42, cross-section images D1 to D4 can be selectively formed as virtual images R1 to R4 at different depth positions.

[0045] 7A to 7C are schematic diagrams showing an example of the configuration of the sequential control unit 40, in which FIG. 7A explains a virtual image that is selectively hidden, FIG. 7B shows an example of the light-shielding unit 42, and FIG. 7C shows an example of capturing virtual images R1 to R4 from viewpoint E. FIGS. 7A to 7C show an example in which the sequential control unit 40 hides only the cross-sectional image D1 and displays the cross-sectional images D2 to D4. As shown in FIG. 7B, in the light-shielding unit 42 of the sequential control unit 40, a transmissive region 43a is arranged at a position corresponding to the cross-sectional images D2 to D4, and a light-shielding region 43b is arranged at a position corresponding to the cross-sectional image D1.

[0046] When looking from viewpoint E toward beam splitter BSM, as shown in Fig. 7(c), cross-section image D1 is not displayed at the imaging position of virtual image R1, but cross-section images D2 to D4 are displayed at the imaging positions of virtual images R2 to R4. Therefore, it can be confirmed that virtual images R2 to R4 of cross-section images D2 to D4 can be selectively formed as indicated by the diagonal lines in Fig. 7(a). Therefore, by the sequential control unit 40 changing the positions of the transmission region 43a and the light-blocking region 43b in the light-blocking unit 42, cross-section images D1 to D4 can be selectively formed as virtual images R1 to R4 at different depth positions.

[0047] In the image projection device 110 of this embodiment, the cross-section image acquisition unit 10 acquires a plurality of different cross-section images D1 to D4 from a virtual three-dimensional shape, and the imaging optical unit 30 forms the plurality of cross-section images D1 to D4 at different distances from the viewpoint E, thereby improving the expressiveness when virtual images R1 to R4 are formed at a plurality of positions in the depth direction. Furthermore, the sequential control unit 40 selectively switches between the display state and the non-display state of the plurality of image display units 20, thereby selectively forming the virtual images R1 to R4, thereby further improving the expressiveness.

[0048] (Third embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. 8. Description of content overlapping with the first embodiment will be omitted. FIG. 8 is a schematic perspective view showing the configuration of an image projection device 120 according to this embodiment. As shown in FIG. 8, the image projection device 120 includes a plurality of image display units 20, beam splitters BS1 to BS4, beam splitters BSC1 and BSC2, a mirror M1, a retroreflection unit RR, a cross beam splitter XBS, and sequential control units 40a and 40b. In this embodiment, image light of cross-sectional images D1 to D4 displayed on the image display units 20 is formed as virtual images R1 to R4 when passing through the sequential control unit 40.

[0049] This embodiment differs from the first embodiment in that the image display units 20 are arranged separately on the left and right of the viewpoint E, and virtual images R1 to R4 are formed using a cross beam splitter XBS. The combination of beam splitters BS1 to BS4, beam splitters BSC1 and BSC2, mirror M1, retroreflector RR, and cross beam splitter XBS corresponds to the imaging optical unit 30. In Figure 8, the holding unit ST that fixes each part of the imaging optical unit 30 is not shown.

[0050] Beam splitters BSC1 and BSC2 are components that transmit part of the incident light and reflect part of it, and can be partial reflectors with a film formed on their surface to adjust the reflectance. Beam splitters BSC1 and BSC2 are tilted at a 45-degree angle with respect to the traveling direction of the image light from image display unit 20. The light transmittance and reflectance of beam splitters BSC1 and BSC2 can be arbitrarily balanced; for example, the transmittance can be set to 50% and the reflectance to 50%.

[0051] The retroreflector RR is an optical element that reflects incident light while maintaining its focusing ability in the direction of incidence, and can be a retroreflector with a structure in which tiny glass beads are spread on the surface side of a reflective film or a structure using a prism. The retroreflector RR is disposed in the path of the image light transmitted through the beam splitter BSC1. The mirror M1 is also disposed in the path of the image light transmitted through the beam splitter BSC1.

[0052] The cross beam splitter XBS is an optical component in which two beam splitters are arranged so that they intersect, reflecting image light incident from both the left and right sides toward viewpoint E and transmitting external light incident from the side opposite viewpoint E. The cross beam splitter XBS is arranged so that its first reflecting surface is inclined at a 45-degree angle to the traveling direction of the image light from beam splitter BSC1, and its second reflecting surface is inclined at a 45-degree angle to the traveling direction of the image light from beam splitter BSC2.

[0053] The image light of the cross-section image D1 displayed on the image display unit 20 passes through the sequential control unit 40a, is reflected by the beam splitter BS1, passes through the beam splitter BS2 and the beam splitter BSC1, and reaches the retroreflection unit RR. The image light of the cross-section image D1 that reaches the retroreflection unit RR is retroreflected so as to narrow its light diameter, and is again incident on and reflected by the beam splitter BSC1. The image light of the cross-section image D1 reflected by the beam splitter BSC1 is reflected by the first reflecting surface of the cross beam splitter XBS and reaches the viewer's viewpoint E.

[0054] The image light of the cross-section image D2 displayed on the image display unit 20 passes through the sequential control unit 40a, is reflected by the beam splitter BS2, passes through the beam splitter BSC1, and reaches the retroreflection unit RR. The image light of the cross-section image D2 that has reached the retroreflection unit RR is retroreflected so as to narrow its light diameter, and is again incident on and reflected by the beam splitter BSC1. The image light of the cross-section image D2 reflected by the beam splitter BSC1 is reflected by the first reflecting surface of the cross beam splitter XBS and reaches the viewer's viewpoint E.

[0055] The image light of the cross-section image D3 displayed on the image display unit 20 passes through the sequential control unit 40b, is reflected by the beam splitter BS3, passes through the beam splitter BSC2, and reaches the mirror M1. The image light of the cross-section image D3 that has reached the mirror M1 is reflected so as to widen its diameter, and is again incident on and reflected by the beam splitter BSC2. The image light of the cross-section image D3 reflected by the beam splitter BSC2 is reflected by the second reflecting surface of the cross beam splitter XBS, and reaches the viewer's viewpoint E.

[0056] The image light of cross-section image D4 displayed on image display unit 20 passes through sequential control unit 40b, is reflected by beam splitter BS4, passes through beam splitters BS3 and BSC2, and reaches mirror M1. The image light of cross-section image D4 that reaches mirror M1 is reflected so as to widen its diameter, and is again incident on and reflected by beam splitter BSC2. The image light of cross-section image D4 reflected by beam splitter BSC2 is reflected by the second reflecting surface of cross beam splitter XBS and reaches viewer's viewpoint E.

[0057] As described above, the image light of the cross-sectional images D1 to D4 displayed on the image display unit 20 has different optical distances and optical diameters before being reflected by the cross beam splitter XBS. Therefore, the cross-sectional images D1 to D4 are formed as virtual images R1 to R4, respectively, according to the optical distances to the beam splitter BSM and the optical diameters. In the example shown in FIG. 8, the virtual images R1 and R2 are formed at positions closer to the viewpoint E than the cross beam splitter XBS, and the virtual images R3 and R4 are formed at positions farther from the viewpoint E than the cross beam splitter XBS. The virtual images R1 to R4 are formed at positions closer to the viewpoint E in this order.

[0058] A viewer views virtual images R1 to R4 formed at different positions in the depth direction by directing their line of sight toward cross beam splitter XBS from viewpoint E. Furthermore, because cross beam splitter XBS transmits light incident from the virtual images R3 and R4 side (front), external light from in front of image projection device 120 also reaches viewpoint E, and virtual images R1 to R4 are displayed superimposed on the background of the external world in front.

[0059] Furthermore, in this embodiment, since the imaging optical unit 30 uses the cross beam splitter XBS, the retroreflector RR, and the mirror M1, the virtual images R1 and R2 are viewed at a position closer to the viewpoint E than the cross beam splitter XBS, and the virtual images R3 and R4 are viewed at a position farther from the cross beam splitter XBS. This allows the viewer to perceive a three-dimensional image display penetrating the cross beam splitter XBS, thereby improving the expressiveness when the virtual images R1 to R4 are formed at multiple positions in the depth direction. In particular, when the virtual images R1 to R4 are selectively formed using the sequential control units 40a and 40b, the impression that the virtual images R1 to R4 are moving through the cross beam splitter XBS can be given, further improving the expressiveness.

[0060] In the image projection device 120 of this embodiment, the cross-section image acquisition unit 10 acquires multiple different cross-section images D1 to D4 from a virtual three-dimensional shape, and the imaging optical unit 30 images the multiple cross-section images D1 to D4 at different distances from the viewpoint E, thereby improving the expressive power when virtual images R1 to R4 are formed at multiple positions in the depth direction.

[0061] (Fourth embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. 9. Description of details overlapping with the first embodiment will be omitted. FIG. 9 is a schematic perspective view showing the configuration of an image projection device 130 according to this embodiment. As shown in FIG. 9, the image projection device 130 includes a plurality of image display units 20, beam splitters BS1 to BS4, beam splitters BSC1 and BSC2, a mirror M1, a retroreflector RR, prisms PR1 and PR2, holographic optical elements HOE1 to HOE3, sequential control units 40a and 40b, and a light guide plate WG. In this embodiment, image light of cross-sectional images D1 to D4 displayed on the image display units 20 is formed as virtual images R1 to R4 when passing through the sequential control unit 40.

[0062] This embodiment differs from the third embodiment in that holographic optical elements HOE1-HOE3, a light guide plate WG, and prisms PR1 and PR2 are used instead of the cross beam splitter XBS. The combination of beam splitters BS1-BS4, beam splitters BSC1 and BSC2, mirror M1, retroreflection unit RR, prisms PR1 and PR2, holographic optical elements HOE1-HOE3, sequential control units 40a and 40b, and light guide plate WG corresponds to imaging optical unit 30. In Figure 9, the holding unit ST that fixes the various components of imaging optical unit 30 is not shown.

[0063] The holographic optical elements HOE1 to HOE3 are optical components that have a refractive index distribution in their planes and diffract light according to its wavelength to achieve desired optical functions. Holographic optical element HOE1 is disposed on the inclined surface of prism PR1 on the path of the image light from beam splitter BSC1. Holographic optical element HOE2 is disposed on the inclined surface of prism PR2 on the path of the image light from beam splitter BSC2. Holographic optical element HOE3 is disposed midway between holographic optical elements HOE1 and HOE2 on light guide plate WG. Holographic optical element HOE3 diffracts the image light from holographic optical elements HOE1 and HOE2 in the direction of viewpoint E and outputs it. Holographic optical element HOE3 also transmits external light that enters from the side opposite viewpoint E.

[0064] The prisms PR1 and PR2 are optical elements having inclined surfaces inclined with respect to the traveling direction of the image light, and take the incident image light into the light guide plate WG. The light guide plate WG is a plate-shaped optical element that totally reflects the image light incident from the prisms PR1 and PR2 inside, causing it to reach the holographic optical element HOE3. While Fig. 9 shows an example in which holographic optical elements HOE1 to HOE3 are used, a DOE (Diffractive Optical Element), which is a diffractive optical element, may also be used.

[0065] The path of the image light of cross-section images D1 and D2 displayed on image display unit 20 is the same as in the third embodiment until it is reflected by beam splitter BSC1. The image light of cross-section images D1 and D2 reflected by beam splitter BSC1 passes through holographic optical element HOE1, prism PR1, and light guide plate WG and reaches holographic optical element HOE3. The image light of cross-section images D1 and D2 that reaches holographic optical element HOE3 is diffracted by holographic optical element HOE3 and reaches viewer's viewpoint E.

[0066] The path of the image light of cross-section images D3 and D4 displayed on image display unit 20 is the same as in the third embodiment until it is reflected by beam splitter BSC2. The image light of cross-section images D3 and D4 reflected by beam splitter BSC2 passes through holographic optical element HOE2, prism PR2, and light guide plate WG and reaches holographic optical element HOE3. The image light of cross-section images D3 and D4 that reaches holographic optical element HOE3 is diffracted by holographic optical element HOE3 and reaches viewer's viewpoint E.

[0067] As described above, the image light of the cross-sectional images D1 to D4 displayed on the image display unit 20 has different optical distances and optical diameters before being diffracted by the holographic optical element HOE3. Therefore, the cross-sectional images D1 to D4 are formed as virtual images R1 to R4, respectively, according to the optical distances to the holographic optical element HOE3 and the optical diameters. In the example shown in FIG. 9, the virtual images R1 and R2 are formed at positions closer to the viewpoint E than the holographic optical element HOE3, and the virtual images R3 and R4 are formed at positions farther from the viewpoint E than the holographic optical element HOE3. The virtual images R1 to R4 are formed at positions closer to the viewpoint E in this order.

[0068] The viewer visually recognizes virtual images R1 to R4 formed at different positions in the depth direction by directing their gaze in the direction of the holographic optical element HOE3 from viewpoint E. Furthermore, because the holographic optical element HOE3 transmits light incident from the virtual images R3 and R4 side (front), external light from in front of the image projection device 130 also reaches viewpoint E, and the virtual images R1 to R4 are displayed superimposed on the background of the external world in front.

[0069] In the image projection device 130 of this embodiment, virtual images R1 and R2 are also viewed at a position closer to the viewpoint E than the holographic optical element HOE3, while virtual images R3 and R4 are viewed at a position farther away than the holographic optical element HOE3. This allows the viewer to perceive a three-dimensional image display penetrating the holographic optical element HOE3, improving the expressive power when virtual images R1 to R4 are formed at multiple positions in the depth direction. In particular, when the sequential control units 40a and 40b are used to selectively form virtual images R1 to R4, it is possible to give the impression that the virtual images R1 to R4 are moving in front of and behind the holographic optical element HOE3, further improving the expressive power.

[0070] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0071] 100, 110, 120, 130...Image projection device 10...Cutting image acquisition unit 20...Image display section 30...Imaging optical section 40, 40a, 40b...Sequential control section 41...Polarizing plate section 42...Light blocking part 43a...transparent area 43b…shading area R1~R4...Virtual image BS1~BS4, BSM, BSC1, BSC2...Beam splitter XBS...Cross beam splitter M1...Mirror RR...retroreflective part PR1, PR2...Prism HOE1 to HOE3...Holographic optical elements WG…Light guide plate

Claims

1. a cross-sectional image acquisition unit that acquires a plurality of cross-sectional images at different depth positions from a virtual three-dimensional shape; a plurality of image display units that respectively display the plurality of cross-sectional images; irradiating the plurality of cross-sectional images displayed on the plurality of image display units as a plurality of image lights; and an imaging optical unit that forms a plurality of the image lights at different distances from a viewpoint.

2. 2. The image projection device according to claim 1, the imaging optical unit has a display unit that reflects a plurality of the image lights in the direction of the viewpoint, The image projection device is characterized in that the plurality of image lights are formed at positions close to and far from the viewpoint from the display unit.

3. 3. The image projection device according to claim 2, The image projection device, wherein the display unit is a cross beam splitter that reflects the image light from a first direction and a second direction toward the viewing direction.

4. 4. The image projection device according to claim 3, The plurality of image display units include a first imaging unit that irradiates the image light onto the display unit from the first direction and forms an image of the image light at a position close to the viewpoint; and a second imaging unit that irradiates the image light onto the display unit from the second direction and forms an image of the image light at a position far from the viewpoint.

5. 5. The image projection device according to claim 4, the first imaging unit irradiates the image light onto the display unit using a retroreflection unit; The image projection device, wherein the second imaging unit uses a reflecting mirror to irradiate the image light onto the display unit.

6. 2. The image projection device according to claim 1, An image projection device comprising a sequential control unit that switches the projection of the plurality of cross-sectional images over time.

7. 7. The image projection device according to claim 6, The image projection device is characterized in that the sequential control unit switches between a display state and a non-display state of the plurality of image display units.

8. 7. The image projection device according to claim 6, It has a light-blocking section that blocks visible light, The image projection device, wherein the sequential control unit changes the position of the light blocking unit to block at least one of the plurality of image lights.

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