Three-dimensional display device having retroreflector

Abstract

A display device according to an embodiment comprises: a beam splitter which has a first surface and a second surface opposite to the first surface, reflects a part of incident light, and transmits the remaining part of the incident light; a retroreflector facing the second surface of the beam splitter and reflecting incident light back in a direction in which the incident light is incident; and an image projector provided on the second surface side of the beam splitter and emitting light containing an image, wherein the image projector, the beam splitter, and the retroreflector may be disposed such that the light emitted by the image projector is incident on the second surface of the beam splitter at an oblique angle while being diverged, the light reflected by the beam splitter is incident on the retroreflector at an oblique angle while being diverged, and the light reflected by the retroreflector is incident on the second surface of the beam splitter at an oblique angle while being converged.

Description

3D display device equipped with a retroreflector

[0001] The disclosed embodiments relate to a three-dimensional display device having a retroreflector and capable of being manufactured with a thin thickness.

[0002] Generally, 3D images are created based on the principle of stereoscopic vision through the user's two eyes, and binocular parallax, which occurs because the two eyes are separated by about 65 mm, is the most important factor in stereoscopic perception.

[0003] Meanwhile, projection displays that create large screens using ultra-small display panels and magnifying optical systems have limitations in creating 3D images. When creating 3D images on a projection display, there is the inconvenience of users having to wear special glasses. Recently, projection display structures capable of creating 3D images without glasses have been proposed, but they have limitations such as significant brightness loss and difficulty in manufacturing them in a compact size.

[0004] A three-dimensional display device equipped with a retroreflector and capable of being manufactured with a thin thickness is provided.

[0005] In addition, a 3D display device capable of displaying 3D images without glasses is provided.

[0006] A display device according to an embodiment comprises: a beam splitter having a first surface and a second surface opposite to the first surface, which reflects a first portion of incident light and transmits a second portion; a retroreflector facing the second surface of the beam splitter and reflecting the incident light back in the direction in which the incident light is incident; and an image projector provided on the side of the second surface of the beam splitter and emitting light containing an image; wherein the image projector, the beam splitter, and the retroreflector may be arranged such that the light emitted from the image projector diverges obliquely and is incident on the second surface of the beam splitter, the incident light reflected from the beam splitter diverges obliquely and is incident on the retroreflector, and the incident light reflected by the retroreflector converges obliquely and is incident on the second surface of the beam splitter.

[0007] The above-described video projector may include at least two video providing elements that each provide videos with different viewpoints.

[0008] The beam splitter is arranged parallel to a plane along a first axis direction and a second axis direction perpendicular to the first axis direction, light emitted from the image projector travels along the first axis direction, and the at least two image providing elements can be arranged along the second axis direction.

[0009] For example, the retroreflector may be parallel to the beam splitter or tilted at less than 45 degrees relative to the beam splitter.

[0010] It may further include a mirror facing the second surface of the beam splitter and reflecting light emitted from the image projector toward the beam splitter.

[0011] The beam splitter is arranged parallel to a plane along a first axis direction and a second axis direction perpendicular to the first axis direction, and the mirror and the retroreflector may be adjacent to each other along the first axis direction.

[0012] The mirror and the retroreflector can be tilted in opposite directions so that the reflective surface of the mirror and the reflective surface of the retroreflector face each other.

[0013] The mirror is inclined at a first angle with respect to the first axis direction, and the retroreflector is inclined at a second angle with respect to the first axis direction, and the first angle and the second angle may be, for example, greater than 0 degrees and less than 45 degrees.

[0014] The reflective surface of the mirror and the reflective surface of the retroreflector may face each other parallel to the beam splitter.

[0015] The above-mentioned image projector may be provided between the mirror and the beam splitter in a third axis direction perpendicular to the first axis direction and the second axis direction.

[0016] The above image projector is positioned between the mirror and the retroreflector in the first axis direction, and the mirror may be positioned at an angle of less than 45 degrees with respect to the third axis direction.

[0017] The retroreflector may be provided between the beam splitter and the image projector in a third axis direction perpendicular to the first axis direction and the second axis direction.

[0018] The reflective surface of the mirror and the reflective surface of the retroreflector can be perpendicular to each other.

[0019] Light reflected by the retroreflector and transmitted through the beam splitter can converge into a viewing area adjacent to the edge of the beam splitter in the first axis direction.

[0020] The above mirror may be a convex curved mirror having a convex reflective surface.

[0021] The display device may further include a diffusion sheet configured to expand the viewing area by diffusing light reflected from the retroreflector, which is provided on the light path between the beam splitter and the retroreflector.

[0022] The display device may further include an anti-reflection layer provided on a first surface of the beam splitter to reduce the reflection of light incident on the first surface of the beam splitter.

[0023] The display device may further include an optical path changing sheet provided on a first surface of the beam splitter and configured to change the direction of propagation of incident light transmitted from the retroreflector to the beam splitter toward the front of the beam splitter.

[0024] The above-described image projector includes a first image projector that emits a first light containing a first image and a second image projector that emits a second light containing a second image, and the retroreflector includes a first retroreflector provided to reflect back the first light reflected from the beam splitter and a second retroreflector provided to reflect back the second light reflected from the beam splitter, wherein the first image projector and the second image projector are provided adjacent to both edges of the beam splitter, and the first retroreflector and the second retroreflector may be tilted in opposite directions so that the reflective surface of the first retroreflector and the reflective surface of the second retroreflector do not face each other.

[0025] The above-described image projector includes a first image projector that emits a first light containing a first image and a second image projector that emits a second light containing a second image, and the beam splitter and the retroreflector are arranged parallel to each other, and the retroreflector may be arranged between the first image projector and the second image projector.

[0026] Figure 1 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0027] Figure 2 exemplarily shows an arrangement of multiple image providing elements of an image projector of a three-dimensional display device.

[0028] Figure 3 schematically shows the arrangement relationship of the image projector, mirror, and retroreflector.

[0029] FIGS. 4a to 4c exemplarily show the change in the position of the viewing area according to the tilt angle of the mirror.

[0030] Figure 5 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0031] Figure 6 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0032] FIG. 7 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0033] FIG. 8 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0034] FIG. 9 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0035] FIG. 10 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0036] FIG. 11 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0037] FIG. 12 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0038] FIG. 13 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0039] FIG. 14 schematically shows the configuration of a three-dimensional display device according to an embodiment.

[0040] Hereinafter, a three-dimensional display device equipped with a retroreflector will be described in detail with reference to the attached drawings. In the drawings below, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the embodiments described below are merely examples, and various modifications are possible from these embodiments.

[0041] In the following, the expressions "at least one of a, b, or c" and "at least one of a, b, and c" indicate including only a, including only b, including only c, including a and b, including a and c, including b and c, or including all of a, b, and c.

[0042] In the following, terms designated as "upper" or "upper" or "lower" or "lower" may include not only those located directly above, below, left, or right in contact, but also those located above, below, left, or right without contact. A singular expression includes a plural expression unless the context clearly indicates otherwise. Furthermore, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0043] The use of the term "for example" and similar descriptive terms may apply to both the singular and the plural. Unless there is an explicit description of the order of the steps constituting the method, these steps may be performed in a suitable order and are not necessarily limited to the described order.

[0044] Additionally, terms such as "...part," "module," etc., as described in the specification refer to a unit that processes at least one function or operation, and this may be implemented in hardware or software, or as a combination of hardware and software.

[0045] The connections of lines or connecting members between the components shown in the drawings are exemplary representations of functional connections and / or physical or circuit connections, and may be replaced or additionally represented as various functional connections, physical connections, or circuit connections in the actual device.

[0046] All examples or the use of terms are merely for the purpose of describing technical ideas in detail, and unless limited by the claims, the scope is not limited by such examples or terms.

[0047] FIG. 1 schematically shows the configuration of a three-dimensional display device according to an embodiment. Referring to FIG. 1, the three-dimensional display device (100) may include an image projector (110), a mirror (111), a beam splitter (112), and a retroreflector (113).

[0048] The mirror (111) and the retroreflector (113) may be arranged to face each other toward the same surface of the beam splitter (112). For example, the mirror (111) and the retroreflector (113) may be arranged to face the lower surface of the beam splitter (112). To ensure a wide field of view, the size of the retroreflector (113) may be larger than the size of the mirror (111). For example, the length of the reflective surface of the retroreflector (113) along the first axis direction (i.e., the X-axis direction) may be about 2 times, or about 3 times, or about 4 times longer than the length of the reflective surface of the mirror (111) along the first axis direction (i.e., the X-axis direction).

[0049] Assuming that the beam splitter (112) is arranged parallel to a horizontal plane along a first axis direction (i.e., X-axis direction) and a second axis direction (i.e., Y-axis direction) perpendicular to the first axis direction (i.e., X-axis direction), the mirror (111) and the retroreflector (113) may be arranged at an angle with respect to the beam splitter (112). For example, each of the mirror (111) and the retroreflector (113) may have a reflective surface facing the beam splitter (112) at an angle. The mirror (111) and the retroreflector (113) may be adjacent to each other along the first axis direction (i.e., X-axis direction) and tilted in opposite directions. For example, the edges of the mirror (111) and the retroreflector (113) that are closer to each other may be tilted relatively downward in a negative (-) third axis direction (i.e., -Z axis direction) perpendicular to the first axis direction (i.e., X axis direction) and the second axis direction (i.e., Y axis direction), and the edges that are farther from each other may be tilted relatively upward in a positive (+) third axis direction (i.e., +Z axis direction). Thus, the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) may face each other at least partially. Additionally, the mirror (111) and the retroreflector (113) may be spaced apart along the first axis direction (i.e., X axis direction) so as not to overlap each other in the third axis direction (i.e., Z axis direction).

[0050] The three-dimensional display device (100) may further include a housing (101). A beam splitter (112) may form the upper surface of the housing (101). Alternatively, the beam splitter (112) may be provided on the upper surface of the housing (101). Although the beam splitter (112) is shown in FIG. 1 as covering the entire upper portion of the housing (101), it is not necessarily limited thereto. For example, the housing (101) may include a bezel extending along the upper edge portion, and the beam splitter (112) may be supported by the bezel on the upper portion of the housing (101). An image projector (110), a mirror (111), a beam splitter (112), and a retroreflector (113) may be provided within the space formed between the beam splitter (112) and the housing (101).

[0051] The image projector (110) may be provided to obliquely provide light containing an image for the user to view to the mirror (111). For example, the image projector (110) may be provided to obliquely face the reflective surface of the mirror (111). The image projector (110) may be provided on the same side of the beam splitter (112) together with the mirror (111) and the retroreflector (113). For example, if the beam splitter (112) has a first surface outside the three-dimensional display device (100) and a second surface opposite to the first surface, the image projector (110), the mirror (111), and the retroreflector (113) may all face the second surface of the beam splitter (112). In the example illustrated in FIG. 1, the image projector (110) may be provided between the mirror (111) and the beam splitter (112) in the third axis direction (i.e., the Z-axis direction).

[0052] A mirror (111) may be positioned to reflect light emitted from an image projector (110) toward a beam splitter (112). Thus, light emitted from the image projector (110) and reflected by the mirror (111) may be incident on a second surface of the beam splitter (112). The beam splitter (112) may be a semi-transparent mirror that reflects a portion of the incident light and transmits the remainder. For example, the beam splitter (112) may reflect half of the incident light and transmit the remainder. The light reflected by the beam splitter (112) may be incident on a retroreflector (113). The retroreflector (113) may be configured to reflect the incident light back in the direction from which the incident light is incident. The light reflected by the retroreflector (113) may travel in the opposite direction along the direction of incidence and be incident on the second surface of the beam splitter (112). Then, the light passing through the beam splitter (112) can proceed toward a viewing area outside the three-dimensional display device (100). Then, the user can watch the video in the viewing area.

[0053] Light from the image projector (110) to the viewing area may travel along four different paths. For example, the light path from the image projector (110) to the viewing area may include a first light path (L1) from the image projector (110) to the mirror (111), a second light path (L2) from the mirror (111) to the beam splitter (112), a third light path (L3) from the beam splitter (112) to the retroreflector (113), and a fourth light path (L4) from the retroreflector (113) to the viewing area.

[0054] The image projector (110) can emit divergent light with increasing beam angle along the direction of travel. Thus, in the first light path (L1), the light is divergent light. In the first light path (L1), the light can travel at an angle along the positive (+) first axis direction (i.e., +X-axis direction) and the negative (-) third axis direction (i.e., -Z-axis direction). In the second light path (L2), the light is divergent light and can travel at an angle along the positive (+) first axis direction (i.e., +X-axis direction) and the positive (+) third axis direction (i.e., +Z-axis direction). In the third light path (L3), the light is divergent light and can travel at an angle along the positive (+) first axis direction (i.e., +X-axis direction) and the negative (-) third axis direction (i.e., -Z-axis direction). Because the retroreflector (113) returns the incident light in the direction of incidence, the light in the fourth light path (L4) becomes converging light. Additionally, in the fourth light path (L4), the light can travel at an angle along the negative (-) first axis direction (i.e., the -X axis direction) and the positive (+) third axis direction (i.e., the +Z axis direction). Thus, from the first light path (L1) to the third light path (L3), the light travels divergingly along the positive (+) first axis direction (i.e., the +X axis direction), and in the fourth light path (L4), the light travels along the first axis direction (i.e., the -X axis direction) and can converge into the viewing area.

[0055] Since a viewing area is formed as light travels along the fourth light path (L4) through the beam splitter (112), a viewing area may be formed near the edge of the three-dimensional display device (100) or near the edge of the beam splitter (112) in the first axis direction (i.e., X-axis direction) (e.g., adjacently). In particular, a viewing area may be formed near the edge of the three-dimensional display device (100) or near the edge of the beam splitter (112) in the negative first axis direction (i.e., -X-axis direction). For example, a viewing area may be formed outside the edge of the three-dimensional display device (100) or outside the edge of the beam splitter (112) in the negative first axis direction (i.e., -X-axis direction).

[0056] The three-dimensional display device (100) according to the embodiment can be manufactured with a thin thickness through the arrangement structure of the image projector (110), mirror (111), beam splitter (112), and retroreflector (113) described above. For example, the three-dimensional display device (100) according to the embodiment can be applied to notebook PCs, laptop PCs, tabletop PCs, tablet PCs, etc. In addition, according to the embodiment, since light converges and travels toward the viewing area, a relatively bright image can be provided to the viewing area.

[0057] A three-dimensional display device (100) may provide a single two-dimensional image, but may also implement a three-dimensional image by providing multiple images with different viewpoints to a viewing area. To this end, the image projector (110) of the three-dimensional display device (100) may include an array of at least two image providing elements that each provide images with different viewpoints. When the image projector (110) includes an array of at least two image providing elements, the multiple image providing elements may be arranged spaced apart along a second axis direction (i.e., the Y-axis direction). Then, the three-dimensional display device (100) according to the embodiment can implement a three-dimensional image without separate glasses.

[0058] FIG. 2 illustrates an exemplary arrangement of a plurality of image providing elements of an image projector (110) of a three-dimensional display device (100). Referring to FIG. 2, the image projector (110) may include a first image providing element (110a), a second image providing element (110b), a third image providing element (110c), and a fourth image providing element (110d) arranged at regular intervals along a second axis direction (i.e., the Y-axis direction). The first image providing element (110a) may provide a first light (L11) containing a first image having a first viewpoint. The second image providing element (110b) may provide a second light (L12) containing a second image having a second viewpoint different from the first viewpoint. The third image providing element (110c) may provide a third light (L13) containing a third image having a third viewpoint different from the first and second viewpoints. The fourth image providing element (110d) can provide a fourth light (L14) containing a fourth image having a fourth time point different from the first to third time points.

[0059] The first to fourth lights (L11, L12, L13, L14) can be emitted toward a single mirror (111). The first to fourth lights (L11, L12, L13, L14) can be incident on different regions on the mirror (111). For example, the first to fourth lights (L11, L12, L13, L14) can be incident on different regions arranged at regular intervals along the second axis direction (i.e., the Y-axis direction) on the mirror (111). The first to fourth lights (L11, L12, L13, L14) reflected by the mirror (111) can be provided to a viewing area by sequentially traveling along the previously described second light path (L2), third light path (L3), and fourth light path (L4). In the viewing area, the first to fourth lights (L11, L12, L13, L14) may be spaced apart at regular intervals along the second axis direction (i.e., the Y-axis direction).

[0060] Although FIG. 2 illustrates a video projector (110) comprising four video providing elements, the number of video providing elements is not limited to four. For example, the video projector (110) may comprise only two video providing elements. For example, the video projector (110) may comprise only a first video providing element (110a) and a second video providing element (110b). In this case, the first video providing element (110a) may provide an image for the right eye, and the second video providing element (110b) may provide an image for the left eye. The first video providing element (110a) and the second video providing element (110b) may be spaced apart in the second axis direction (i.e., the Y-axis direction) by the distance between the user's left eye and right eye.

[0061] Alternatively, the video projector (110) may include three, four, or five or more video providing elements. In this case, the distance between two immediately adjacent video providing elements may be smaller than the distance between the user's two eyes. Additionally, the difference in viewpoint between two images provided by two immediately adjacent video providing elements may be smaller than the difference in viewpoint between the user's left and right eyes. Then, the user can view images of various more detailed viewpoints over a relatively wide viewing area.

[0062] Meanwhile, the location of the viewing area can be determined by the arrangement relationship of the image projector (110), mirror (111), beam splitter (112), and retroreflector (113). FIG. 3 schematically shows the arrangement relationship of the image projector (110), mirror (111), and retroreflector (113). Referring to FIG. 3, assuming that the beam splitter (112) is arranged parallel to a horizontal plane along the first axis direction (i.e., X-axis direction) and the second axis direction (i.e., Y-axis direction), the mirror (111) can be arranged at a first angle (θ1) with respect to the first axis direction (i.e., X-axis direction). The retroreflector (113) can be arranged at a second angle (θ2) with respect to the first axis direction (i.e., X-axis direction). Here, the first angle (θ1) and the second angle (θ2) may be angles represented as acute angles smaller than 90 degrees from the first axis direction (i.e., the X-axis direction). In this case, the angle between the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) is the third angle (θ3), and the third angle (θ3) may have the relationship θ3 = 180 - (θ1 + θ2). The image projector (110) may be arranged to be inclined at a fourth angle (θ4) with respect to the reflective surface of the mirror (111). For example, among the light emitted from the image projector (110), the central light (L0) may be incident on the mirror (111) at the fourth angle (θ4). The image projector (110) may emit light at a predetermined diffusion angle (α). Here, the diffusion angle (α) may be defined as the angle between the peripheral light among the light emitted from the image projector (110).

[0063] According to an embodiment, the position of the viewing area and the size of the image can be determined according to various factors such as a first angle (θ1) to a fourth angle (θ4), a distance along the first axis direction (i.e., X-axis direction) between the mirror (111) and the retroreflector (113), a distance along the third axis direction (i.e., Z-axis direction) between the mirror (111) and the beam splitter (112), a distance along the third axis direction (i.e., Z-axis direction) between the retroreflector (113) and the beam splitter (112), and a diffusion angle (α) of the image projector (110). In the design process of a three-dimensional display device (100), the optimal position of the viewing area is determined, and according to the determined position of the viewing area, design values ​​regarding the first angle (θ1) to the fourth angle (θ4), the distance along the first axis direction (i.e., X-axis direction) between the mirror (111) and the retroreflector (113), the distance along the third axis direction (i.e., Z-axis direction) between the mirror (111) and the beam splitter (112), and the distance along the third axis direction (i.e., Z-axis direction) between the retroreflector (113) and the beam splitter (112) are determined, and then the three-dimensional display device (100) can be manufactured according to these design values.

[0064] In one example, the three-dimensional display device (100) may have a fixed optimal viewing area position according to a prior design. In another example, assuming that the positions of the image projector (110), mirror (111), beam splitter (112), and retroreflector (113) are fixed within the housing (101), it is also possible to adjust the position of the viewing area to suit the user by adjusting at least one of the first angle (θ1) to the fourth angle (θ4). For example, referring again to FIG. 1, the three-dimensional display device (100) may further include a controller (120) for adjusting at least one of the first angle (θ1) to the fourth angle (θ4). Although the controller (120) is shown outside the housing (101) for convenience in the drawing, the controller (120) may be mounted inside the housing (101). The controller (120) may include an input panel, such as a keypad or touchpad, for receiving commands from the user. The controller (120) may be configured to adjust the tilt angle of at least one of the image projector (110), mirror (111), and retroreflector (113) according to a user's command. For example, the controller (120) may include a motor or actuator for adjusting the tilt of each of the image projector (110), mirror (111), and retroreflector (113), and may adjust the tilt angle of at least one of the image projector (110), mirror (111), and retroreflector (113) by electrically controlling the operation of the motor or actuator.

[0065] FIGS. 4a to 4c exemplarily show a change in the position of the viewing area according to the tilt angle of the mirror (111). Referring to FIGS. 4a to 4c, as the tilt angle of the mirror (111), i.e., the first angle (θ1), decreases, the position of the viewing area can move in the positive (+) first axis direction (i.e., the X-axis direction). In other words, when the first angle (θ1) of the mirror (111) decreases, the position of the viewing area moves in the first axis direction (i.e., X-axis direction) from the edge of the three-dimensional display device (100) toward the center of the three-dimensional display device (100) or from the edge of the beam splitter (112) toward the center of the beam splitter (112), and when the first angle (θ1) of the mirror (111) increases, the position of the viewing area can move in the first axis direction (i.e., X-axis direction) from the center of the three-dimensional display device (100) toward the edge or from the center of the beam splitter (112) toward the edge. When the fourth angle (θ4) of the video projector (110) increases, the position of the viewing area moves from the edge of the three-dimensional display device (100) toward the center in the first axis direction (i.e., X-axis direction), and when the fourth angle (θ4) of the video projector (110) decreases, the position of the viewing area can move from the center of the three-dimensional display device (100) toward the edge in the first axis direction (i.e., X-axis direction).

[0066] As illustrated in FIG. 4c, it is also possible for the mirror (111) and the retroreflector (113) to be adjacent to each other in parallel in the first axis direction (i.e., the X-axis direction) on the same plane. In this case, the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) may face each other parallel to the beam splitter (112). In other words, the first angle (θ1) of the mirror (111) and the second angle (θ2) of the retroreflector (113) may be 0 degrees, and the third angle (θ3) between the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) may be 180 degrees. Thus, the first angle (θ1) and the second angle (θ2) may be at least 0 degrees, and the third angle (θ3) may be 180 degrees or less. Meanwhile, if the first angle (θ1) and the second angle (θ2) become excessively large, the thickness of the three-dimensional display device (100) may increase. Considering the thickness of the three-dimensional display device (100) and the position of the appropriate viewing area, the first angle (θ1), the second angle (θ2), and the fourth angle (θ4) may be, for example, less than 45 degrees or 30 degrees or less, and the third angle (θ3) may be, for example, 90 degrees or more or 120 degrees or more. In particular, the second angle (θ2) of the retroreflector (113) may be, for example, 0 degrees or more and less than 45 degrees, or 0 degrees or more and 30 degrees or less, or 0 degrees or more and 25 degrees or less. Accordingly, the retroreflector (113) may be parallel to the beam splitter (112), or tilted less than 45 degrees, or 30 degrees or less, or 25 degrees or less relative to the beam splitter (112).

[0067] FIG. 5 schematically shows the configuration of a three-dimensional display device according to an embodiment. In the example illustrated in FIG. 1, the beam splitter (112) is described as a simple semi-transparent mirror, but the beam splitter (112) may be a polarizing beam splitter that reflects light of a specific polarization component and transmits light of another polarization component. Referring to FIG. 5, the three-dimensional display device (100a) may further include a polarizing plate (114) provided in the light path between the image projector (110) and the mirror (111), and a quarter-wave plate (115) provided in the light path between the beam splitter (112) and the retroreflector (113). The polarizing plate (114) may be, for example, an absorption-type polarizing plate that transmits only light having a first linear polarization component and absorbs light having a second linear polarization component perpendicular to the first linear polarization component. The beam splitter (112) may be a polarizing beam splitter that reflects light having a first linear polarization component and transmits light having a second linear polarization component. The remaining configuration of the three-dimensional display device (100a) shown in FIG. 5 may be the same as that of the three-dimensional display device (100) shown in FIG. 1.

[0068] In the above configuration, among the light emitted from the image projector (110), only the light having a first linear polarization component can pass through the polarizer (114) and then be incident on the beam splitter (112). The light having the first linear polarization component is reflected by the beam splitter (112) and then passes through the quarter-wave plate (115) to have a first circular polarization component. The light having the first circular polarization component is reflected by the retroreflector (113) and becomes light having a second circular polarization component having a direction opposite to that of the first circular polarization component. The light having the second circular polarization component passes through the quarter-wave plate (115) and becomes light having a second linear polarization component, which can then pass through the beam splitter (112).

[0069] FIG. 6 schematically shows the configuration of a three-dimensional display device according to an embodiment. Up until now, the mirror (111) has been described as a flat mirror, but the mirror (111) may be a curved mirror as needed. For example, referring to FIG. 6, the mirror (111) of the three-dimensional display device (100b) may be a convex curved mirror having a convex reflective surface. When the mirror (111) is a convex curved mirror, the divergence angle of light in the second light path (L2), the third light path (L3), and the fourth light path (L4) increases, so that the image can be further magnified. When the diffusion angle (α) of the image projector (110) is relatively small or it is difficult to secure a sufficient light path length within the housing (101), the image can be magnified through the convex curved mirror to realize an image of sufficient size.

[0070] FIG. 7 schematically shows the configuration of a three-dimensional display device according to an embodiment. Up until now, it has been described that an image projector (110) is positioned between a beam splitter (112) and a mirror (111) in the third axis direction (i.e., Z-axis direction), and that light in the first light path (L1) travels obliquely along the positive (+) first axis direction (i.e., +X-axis direction) and the negative (-) third axis direction (i.e., -Z-axis direction). However, it is also possible to configure the arrangement between the beam splitter (112) and the mirror (111) differently. Referring to FIG. 7, in the three-dimensional display device (100c), the image projector (110) may be positioned between the mirror (111) and a retroreflector (113) in the first axis direction (i.e., X-axis direction). Additionally, the image projector (110) may face the lower part of the reflective surface of the mirror (111) in the third axis direction (i.e., Z-axis direction). For example, the image projector (110) may be positioned below the retroreflector (113) in the third axis direction (i.e., the Z-axis direction). In other words, the retroreflector (113) may be positioned between the beam splitter (112) and the image projector (110) in the third axis direction (i.e., the Z-axis direction).

[0071] In this case, light in the first light path (L1) can travel along the negative (-) first axis direction (i.e., -X-axis direction) and the positive (+) third axis direction (i.e., +Z-axis direction). Additionally, the first angle (θ1), which is the inclination angle of the mirror (111), can be determined based on the third axis direction (i.e., Z-axis direction) rather than the first axis direction (i.e., X-axis direction). That is, the mirror (111) can be tilted at the first angle (θ1) with respect to the third axis direction (i.e., Z-axis direction). For example, the first angle (θ1) of the mirror (111) with respect to the third axis direction (i.e., Z-axis direction) can be less than 45 degrees or less than 30 degrees.

[0072] FIG. 8 schematically shows the configuration of a three-dimensional display device according to an embodiment. Referring to FIG. 8, a mirror (111) may be arranged perpendicular to the first axis direction (i.e., X direction) and parallel to the third axis direction (i.e., Z axis direction). In other words, the first angle (θ1) of the mirror (111) with respect to the third axis direction (i.e., Z axis direction) may be 0 degrees. A retroreflector (113) may be arranged parallel to the first axis direction (i.e., X direction). In other words, the second angle (θ2) of the retroreflector (113) with respect to the first axis direction (i.e., X axis direction) may be 0 degrees. In this case, the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) may be perpendicular to each other. However, this is not necessarily limited thereto, and as previously explained, the retroreflector (113) may be tilted less than 45 degrees, or 30 degrees or less, or 25 degrees or less with respect to the first axis direction (i.e., X-axis direction). In this case, the third angle (θ3) between the reflective surface of the mirror (111) and the reflective surface of the retroreflector (113) may be less than 90 degrees.

[0073] FIG. 9 schematically shows the configuration of a three-dimensional display device according to an embodiment. Up to this point, it has been described that a mirror (111) is provided in the light path between the image projector (110) and the beam splitter (112). The mirror (111) is provided to bend the light path to secure a sufficient length of light path from the image projector (110) to the beam splitter (112). However, if a sufficient length of light path can be secured between the image projector (110) and the beam splitter (112) without the mirror (111), or if the diffusion angle (α) of the image projector (110) is sufficiently large, the mirror (111) may be omitted. Referring to FIG. 9, the three-dimensional display device (100d) does not include a mirror (111), and the image projector (110) may be provided inclined toward the beam splitter (112). In this case, light emitted from the image projector (110) can travel toward the beam splitter (112) at an angle along the positive (+) first axis direction (i.e., +X axis direction) and the positive (+) third axis direction (i.e., +Z axis direction).

[0074] FIG. 10 schematically shows the configuration of a three-dimensional display device according to an embodiment. Referring to FIG. 10, the three-dimensional display device (100e) may further include a diffusion sheet (116) provided on the light path between a beam splitter (112) and a retroreflector (113). For example, the diffusion sheet (116) may be provided on the reflective surface of the retroreflector (113). The diffusion sheet (116) may be positioned to be in direct contact with the reflective surface of the retroreflector (113), or it may be positioned with a gap from the reflective surface of the retroreflector (113). The diffusion sheet (116) may be configured to extend the viewing area in the horizontal direction or the vertical direction. To this end, the diffusion sheet (116) may diffuse the light reflected from the retroreflector (113) in a second axis direction (i.e., the Y-axis direction) or a third axis direction (i.e., the Z-axis direction). This diffusion sheet (116) may be, for example, a lenticular sheet including a plurality of lenticular lenses, or an anisotropic diffuser such as a holographic diffuser.

[0075] FIG. 11 schematically shows the configuration of a three-dimensional display device according to an embodiment. Referring to FIG. 11, the three-dimensional display device (100f) may further include an anti-reflection layer (117) for reducing image noise. The anti-reflection layer (117) may be provided on the outer surface of a beam splitter (112). For example, if the beam splitter (112) has a first surface on the outer side of the three-dimensional display device (100f) and a second surface opposite to the first surface, the anti-reflection layer (117) may be provided on the first surface of the beam splitter (112), and an image projector (110), a mirror (111), and a retroreflector (113) may be provided to face the second surface of the beam splitter (112). The anti-reflection layer (117) can improve image clarity by preventing or reducing light incident on the first surface of the beam splitter (112) from the outside from being reflected into the viewing area.

[0076] FIG. 12 schematically shows the configuration of a three-dimensional display device according to an embodiment. Referring to FIG. 12, the three-dimensional display device (100g) may further include an optical path changing sheet (118) that changes the position of the viewing area toward the front of the three-dimensional display device (100g). Because the aforementioned three-dimensional display device forms a viewing area near the edge of the three-dimensional display device or near the edge of the beam splitter (112), it may be difficult to apply it to a monitor or TV, etc. By using the optical path changing sheet (118), a viewing area can be formed at the front of the three-dimensional display device (100g) or at the front of the beam splitter (112), so the three-dimensional display device (100g) can be applied, for example, to a monitor or TV, etc.

[0077] The optical path changing sheet (118) may be provided on the outer surface of the beam splitter (112). For example, if the beam splitter (112) has a first surface on the outside of the three-dimensional display device (100g) and a second surface opposite to the first surface, the optical path changing sheet (118) may be provided on the first surface of the beam splitter (112). The optical path changing sheet (118) may be, for example, a prism sheet comprising a plurality of micro prisms. The optical path changing sheet (118) may be configured to change the direction of propagation of light that passes through the beam splitter (112) from the retroreflector (113) and travels obliquely toward the edge of the beam splitter (112) in the first axial direction (i.e., X-axis direction) toward the front of the three-dimensional display device (100g) or toward the front of the beam splitter (112).

[0078] In a three-dimensional display device (100g) further comprising an optical path changing sheet (118), light from an image projector (110) to a viewing area may travel along five different paths. For example, the optical path from the image projector (110) to a viewing area may include a first optical path (L1) from the image projector (110) to a mirror (111), a second optical path (L2) from the mirror (111) to a beam splitter (112), a third optical path (L3) from the beam splitter (112) to a retroreflector (113), a fourth optical path (L4) from the retroreflector (113) to an optical path changing sheet (118), and a fifth optical path (L5) from the optical path changing sheet (118) to a viewing area. Light reflected from the retroreflector (113) and transmitted through the beam splitter (112) can converge into the viewing area while traveling along a direction nearly perpendicular to the first surface of the beam splitter (112) in the fifth light path (L5), that is, along the third axis direction (i.e., the Z-axis direction).

[0079] FIG. 13 schematically shows the configuration of a three-dimensional display device according to an embodiment. Although the aforementioned display device has been described as providing only one viewing area, it is also possible to provide two or more viewing areas. Referring to FIG. 13, the three-dimensional display device (100h) may include a beam splitter (112), a first image projector (110A), a second image projector (110B), a first mirror (111A), a second mirror (111B), a first retroreflector (113A), and a second retroreflector (113B). The first image projector (110A) and the second image projector (110B) may be provided near both edges of the beam splitter (112) in the first axis direction (i.e., the X-axis direction). The first image projector (110A) and the second image projector (110B) may be arranged symmetrically with respect to each other, but are not necessarily limited thereto. The first image projector (110A) emits first light containing the first image, and the second image projector (110B) emits second light containing the second image. The first image and the second image may be the same image, or they may be different images.

[0080] A first mirror (111A) may be provided to reflect a first light emitted from a first image projector (110A) to a beam splitter (112), and a second mirror (111B) may be provided to reflect a second light emitted from a second image projector (110B) to a beam splitter (112). The first light reflected from the first mirror (111A) may travel obliquely toward the beam splitter (112) along a positive (+) first axis direction (i.e., +X-axis direction) and a positive (+) third axis direction (i.e., +Z-axis direction), and the second light reflected from the second mirror (111B) may travel obliquely toward the beam splitter (112) along a negative (-) first axis direction (i.e., -X-axis direction) and a positive (+) third axis direction (i.e., +Z-axis direction). In one example, the first mirror (111A) and the second mirror (111B) may be positioned symmetrically with respect to each other, but are not necessarily limited thereto.

[0081] A first retroreflector (113A) may be configured to reflect back the first light reflected from the beam splitter (112) in a negative (-) first axis direction (i.e., -X-axis direction), and a second retroreflector (113B) may be configured to reflect back the second light reflected from the beam splitter (112) in a positive (+) first axis direction (i.e., +X-axis direction). The first retroreflector (113A) and the second retroreflector (113B) may be tilted in opposite directions so that the reflective surface of the first retroreflector (113A) and the reflective surface of the second retroreflector (113B) do not face each other. The first light reflected from the first retroreflector (113A) passes through the beam splitter (112) along the negative (-) first axis direction (i.e., -X-axis direction) and the positive (+) third axis direction (i.e., +Z-axis direction) and travels obliquely toward the first viewing area, and the second light reflected from the second retroreflector (113B) passes through the beam splitter (112) along the positive (+) first axis direction (i.e., +X-axis direction) and the positive (+) third axis direction (i.e., +Z-axis direction) and travels obliquely toward the second viewing area. The first retroreflector (113A) and the second retroreflector (113B) may be arranged symmetrically with respect to each other, but are not necessarily limited thereto.

[0082] According to an embodiment, two viewing areas may be formed near both edges of a three-dimensional display device (100h). For example, a first viewing area may be formed near the edge of the three-dimensional display device (100h) in the direction of a negative (-) first axis (i.e., the -X-axis direction), and a second viewing area may be formed near the edge of the three-dimensional display device (100h) in the direction of a positive (+) first axis (i.e., the +X-axis direction). Then, a user can view a three-dimensional image at each of the two edges of the three-dimensional display device (100h). When the first image projector (110A) and the second image projector (110B) are symmetrically positioned relative to each other, the first mirror (111A) and the second mirror (111B) are symmetrically positioned relative to each other, and the first retroreflector (113A) and the second retroreflector (113B) are symmetrically positioned relative to each other, the positions of the first viewing area and the second viewing area may be symmetrical, but are not necessarily limited thereto.

[0083] FIG. 13 illustrates a case where two viewing areas are formed on both sides in the first axis direction (i.e., the X-axis direction), but is not limited thereto. For example, two image forming devices, two mirrors, and two retroreflectors may also be provided on both sides in the second axis direction (i.e., the Y-axis direction). Then, two additional viewing areas may be formed on both sides in the second axis direction (i.e., the Y-axis direction).

[0084] FIG. 14 schematically shows the configuration of a three-dimensional display device according to an embodiment. The three-dimensional display device (100h) shown in FIG. 13 includes two retroreflectors, namely a first retroreflector (113A) and a second retroreflector (113B), but it is also possible to use only one retroreflector when the retroreflectors are arranged parallel to the beam splitter (112). Referring to FIG. 14, the three-dimensional display device (100i) may include a beam splitter (112), a first image projector (110A), a second image projector (110B), a first mirror (111A), a second mirror (111B), and a retroreflector (113).

[0085] The beam splitter (112) and the retroreflector (113) may be arranged parallel to each other. For example, the beam splitter (112) and the retroreflector (113) may be arranged parallel to a horizontal plane along the first axis direction (i.e., X-axis direction) and the second axis direction (i.e., Y-axis direction), and spaced apart from each other along the third axis direction (i.e., Z-axis direction). The first image projector (110A) and the second image projector (110B) may be arranged on each side of the beam splitter (111) and the retroreflector (113) in the first axis direction (i.e., X-axis direction). Additionally, the first mirror (111A) and the second mirror (111B) may also be arranged on each side of the beam splitter (111) and the retroreflector (113) in the first axis direction (i.e., X-axis direction). In other words, the retroreflector (113) can be provided between the first image projector (110A) and the second image projector (110B) or between the first mirror (111A) and the second mirror (111B) in the first axis direction (i.e., the X-axis direction).

[0086] Although the three-dimensional display device equipped with the aforementioned retroreflector has been described with reference to the embodiments illustrated in the drawings, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the rights is defined in the claims, not in the foregoing description, and all variations within the scope of equivalence should be interpreted as being included within the scope of the rights.

Claims

1. A beam splitter having a first surface and a second surface opposite to the first surface, which reflects a first portion of incident light and transmits a second portion of incident light; A retroreflector facing the second surface of the beam splitter and reflecting the incident light back in the direction in which the incident light is incident; and It includes an image projector provided on the second surface side of the beam splitter and emitting light containing an image; A display device comprising an image projector, a beam splitter, and a retroreflector, wherein light emitted from the image projector is incident on a second surface of the beam splitter while diverging at an angle, incident light reflected from the beam splitter is incident on a retroreflector while diverging at an angle, and incident light reflected by the retroreflector is incident on a second surface of the beam splitter while converging at an angle.

2. In Paragraph 1, The above-described video projector includes at least two video providing elements that each provide videos with different viewpoints, and A display device wherein the beam splitter is arranged parallel to a plane along a first axis direction and a second axis direction perpendicular to the first axis direction, light emitted from the image projector travels along the first axis direction, and the at least two image providing elements are arranged along the second axis direction.

3. In Paragraph 1, A display device in which the retroreflector is parallel to the beam splitter or tilted at less than 45 degrees with respect to the beam splitter.

4. In Paragraph 1, It further includes a mirror facing the second surface of the beam splitter and reflecting light emitted from the image projector toward the beam splitter, A display device in which the beam splitter is arranged parallel to a plane along a first axis direction and a second axis direction perpendicular to the first axis direction, and the mirror and the retroreflector are adjacent to each other along the first axis direction.

5. In Paragraph 4, A display device in which the mirror and the retroreflector are tilted in opposite directions so that the reflective surface of the mirror and the reflective surface of the retroreflector face each other.

6. In Paragraph 4, A display device wherein the mirror is inclined at a first angle with respect to a first axis direction and the retroreflector is inclined at a second angle with respect to the first axis direction, and the first angle and the second angle are greater than or equal to 0 degrees and less than 45 degrees.

7. In Paragraph 4, A display device in which the reflective surface of the mirror and the reflective surface of the retroreflector face each other parallel to the beam splitter.

8. In Paragraph 4, The above-described image projector is a display device arranged between the mirror and the beam splitter in a third axis direction perpendicular to the first axis direction and the second axis direction.

9. In Paragraph 4, The above image projector is provided between the mirror and the retroreflector in the first axis direction, and The above mirror is arranged to be inclined at an angle of less than 45 degrees with respect to the third axis direction, and A display device in which the retroreflector is provided between the beam splitter and the image projector in a third axis direction perpendicular to the first axis direction and the second axis direction.

10. In Paragraph 4, The above image projector is provided between the mirror and the retroreflector in the first axis direction, and The above mirror is arranged to be inclined at an angle of less than 45 degrees with respect to the third axis direction, and A display device in which the reflective surface of the mirror and the reflective surface of the retroreflector are perpendicular to each other.

11. In Paragraph 4, A display device in which incident light reflected by the retroreflector and transmitted through the beam splitter converges into a viewing area adjacent to the edge of the beam splitter in the first axis direction.

12. In Paragraph 1, A display device further comprising a diffusion sheet provided on the light path between the beam splitter and the retroreflector, configured to diffuse light reflected from the retroreflector to expand the viewing area.

13. In Paragraph 1, A display device further comprising an optical path changing sheet provided on a first surface of the beam splitter, configured to change the direction of propagation of incident light transmitted from the retroreflector to the beam splitter toward the front of the beam splitter.

14. In Paragraph 1, The above-mentioned image projector includes a first image projector that emits a first light containing a first image and a second image projector that emits a second light containing a second image, and The above retroreflector includes a first retroreflector arranged to reflect back a first light reflected from the beam splitter and a second retroreflector arranged to reflect back a second light reflected from the beam splitter. The first image projector and the second image projector are provided adjacent to both edges of the beam splitter, and A display device in which the first retroreflector and the second retroreflector are tilted in opposite directions so that the reflective surface of the first retroreflector and the reflective surface of the second retroreflector do not face each other.

15. In Paragraph 1, The above-mentioned image projector includes a first image projector that emits a first light containing a first image and a second image projector that emits a second light containing a second image, and The beam splitter and the retroreflector are arranged parallel to each other, The above retroreflector is a display device provided between the first image projector and the second image projector.

Images