Shielded object visualization device

Abstract

To provide shielded object visualization technology that enables the structure around a shield to be constructed in a compact size.SOLUTION: Light from a shielded object O on the other side of a shield S reaches a visual recognition position V passing through a bypass optical path formed by first and second reflectors 1, 3 and an image propagation element 2. Light from the shielded object O is reflected by the first reflector 1 and proceeds laterally before reaching the image propagation element 2 where an image is propagated, arriving at the visual recognition position V after being reflected by the second reflector 3. The image propagation element 2 includes a first prism sheet 4 which light from the first reflector 1 enters, a second prism sheet 5 disposed on the visual recognition position V side in a visual recognition direction with respect to the first prism sheet 4, and a reflector 6 for propagation. The first and second prism sheets 4, 5 respectively have long and minute linear prism parts 41, 51 in a direction perpendicular to the surface where the bypass optical path is formed.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The invention of this application relates to a device for visualizing an object to be shielded that is shielded by a shielding object and not visible.

Background Art

[0002] From the viewpoints of safety and improvement of the landscape, there is a need to visualize an object to be shielded that is shielded by a shielding object. For example, in various moving objects such as automobiles, it has been considered to improve the visibility in the driver's seat to enhance safety. As an example, technologies for enabling a driver to visually recognize an object to be shielded that is shielded by, for example, the front pillar of an automobile have been conventionally studied.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Among these, as patent documents, many technologies are disclosed in which an object to be shielded is photographed by a camera from another angle (an angle where it is not shielded) and displayed on a display arranged in front of the shielding object. However, in this type of technology, the configuration tends to be large-scale, resulting in high costs, and since it requires a power source, visualization cannot be performed when the power source is turned off. As a technology that does not particularly require a power source, a technology called so-called "cloaking" is disclosed in Patent Document 1 and Patent Document 2. In the technologies disclosed in these documents, an optical path that detours light from the object to be shielded is formed around the shield, and the object to be shielded is made visible by reaching the viewing position in front of the shield. In this specification, the viewing position is the position of the eyes of the person who is trying to view the object to be shielded. It is not always a human being who views, and there may be a case where it is the position where an object (for example, an image sensor) that is trying to capture an image of the object to be shielded exists.

[0005] According to the technologies of Patent Documents 1 and 2 above, visualization can be performed without particularly requiring a power source. However, in Patent Document 1, since the optical path that detours around the shield is formed by a combination of corner cubes, the device configuration protrudes greatly on both sides of the shield. For this reason, it is in a state where a shield is additionally added in addition to the original shield, and it does not meet the purpose of improving visibility. A configuration in which the corner cube part is half-mirrored has also been proposed, but there is a problem that the amount of light passing through the detoured optical path decreases accordingly. In addition, when a structure is provided so as to protrude greatly to the side, since it is not an element of the shield itself, a sense of incongruity is likely to occur. For example, when the shield is the front pillar of an automobile, it is in a state where the front pillar becomes unnecessarily wide, a sense of incongruity is likely to occur, and the original window area is also narrowed.

[0006] Patent Document 2 discloses a configuration in which Fresnel lenses are arranged on the incident side (the side of the object to be shielded) and the emission side (the side of the viewing position). The Fresnel lens on the incident side detours the light, reflects it with mirrors arranged on both sides of the shield, and reaches the Fresnel lens on the emission side. The Fresnel lens on the emission side returns the light to its original direction and reaches the viewing position. In the configuration of Patent Document 2, since the elements of the device do not significantly occupy the areas on both sides of the shielding object, there is no problem like that in Patent Document 1. However, since Patent Document 2 employs a transmissive Fresnel lens, due to the refractive index relationship, the separation distance between the incident-side Fresnel lens and the exit-side Fresnel lens has to be increased, resulting in the drawback that the device becomes large in the viewing direction (the direction connecting the shielded object and the viewing position).

[0007] The invention of this application aims to solve these problems of the prior art, and aims to provide an excellent shielded object visualization technique capable of making the structure around the shielding object compact.

Means for Solving the Problems

[0008] To solve the above problems, in this specification, an invention of a shielded object visualization device is disclosed. The shielded object visualization device according to the disclosed invention is a device that visualizes a shielded object on the far side of a shielding object and shielded by the shielding object at a viewing position in front of the shielding object. This device when the direction connecting the position of the shielding object and the viewing position is defined as the viewing direction, a first reflector that reflects the light that has traveled from the shielded object along the viewing direction towards the shielding object to the side in front of the shielding object; an image propagation element disposed at the position where the light reflected by the first reflector is incident; and a second reflector that reflects the light from the image propagation element to reach the viewing position and is provided with. The image propagation element includes a first prism sheet disposed in the region where the light from the first reflector is incident, a second prism sheet disposed on the viewing position side in the viewing direction with respect to the first prism sheet, and a propagation reflector. Each prism sheet is an element in which a plurality of prism parts are arranged. Each prism part of the first prism sheet propagates the image formed by the light from the first reflector to the second prism sheet. It directs the light from the first reflector towards the propagation reflector, reflects it with the propagation reflector, and causes it to reach the second prism sheet. The second reflector reflects the light from the second prism sheet, causes it to travel in the viewing direction, and reach the viewing position, making the propagated image visible at the viewing position. Also, in order to solve the above problems, in the obscured object visualization device according to the disclosed invention, each prism part of the first prism sheet can be formed with an inclined surface such that when the light reflected by the propagation reflector reaches the second prism sheet and the image is propagated, the image in the second prism sheet becomes an inverted image across the boundary surface between the first and second prism sheets perpendicular to the viewing direction. Also, in order to solve the above problems, the obscured object visualization device according to the disclosed invention can have a configuration where the inclined surface of each prism part of the first prism sheet is a surface that reflects light and reaches the propagation reflector, and the inclined surface of each prism part of the second prism sheet is a surface that reflects light and reaches the second reflector, and the angles of the inclined surfaces of each prism part of the first prism sheet and the second prism sheet with respect to the viewing direction increase as they move away from the boundary surface. Also, in order to solve the above problems, the obscured object visualization device according to the disclosed invention can have a configuration where the first and second prism sheets have their prism parts arranged along the viewing direction, and the width of each prism part in the viewing direction is less than the width at which the inversion of the image in each prism part unit can be visually recognized by the human eye. Also, in order to solve the above problems, in the obscured object visualization device according to the disclosed invention, the image propagation element can be an element that transmits light traveling from a position outside the obscured object towards the viewing position.

Advantages of the Invention

[0009] As described below, according to the occluded object visualization device according to the disclosed invention, an image propagation element is provided in the detour optical path of the light that has traveled toward the occluding object. Since the image propagation element includes a prism sheet and a propagation reflector and propagates an image, the detour optical path can be made compact, and the structure does not protrude significantly laterally for visualizing the occluded object. Therefore, an excellent occluded object visualization device that can make the structure around the occluding object compact is provided. In addition, when the light reflected by the propagation reflector reaches the second prism sheet and the image is propagated, according to the configuration in which the slopes of the prism portions of the first prism sheet are formed so that the image in the second prism sheet becomes an image inverted across the boundary surface between the first and second prism sheets perpendicular to the viewing direction, the inversion of the image in units of the prism sheet is eliminated. Therefore, an occluded object visualization device that is preferably used when image inversion becomes a problem is provided. In addition, according to the configuration in which the prism portions are arranged along the viewing direction and the width of each prism portion in the viewing direction is less than the width at which the inversion of the image in the unit of each prism portion is visually recognized by the human eye, the inversion of the image in units of each prism portion is not visually recognized, so visualization in a state without discomfort is achieved. In addition, according to the configuration in which the image propagation element is an optical element that transmits light from a position outside the occluded object toward the viewing position, it is possible to avoid the image propagation element becoming another occluding object. Therefore, an occluded object visualization device with a suitable visualization situation is provided.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

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Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0011] Next, embodiments for carrying out the invention of this application will be described. FIG. 1 is a schematic plan view of an object-to-be-blocked visualization device according to the first embodiment. The object-to-be-blocked visualization device according to the embodiment is an object-to-be-blocked visualization device that visualizes an object O that is on the other side of an obstacle S and is blocked by the obstacle S at a viewing position in front of the obstacle S. Visualization means making it visible. For example, it means that there is a human eye there and it can be seen when trying to look. As another example, it means that there is, for example, an image sensor there and it can be imaged if the power is on. In FIG. 1, the viewing position is indicated by V. Also, in the following description, the direction connecting the position of the obstacle S and the viewing position V is called the viewing direction.

[0012] As shown in FIG. 1, the object-to-be-blocked visualization device according to the embodiment includes a first reflector 1, an image propagation element 2, and a second reflector 3. The first reflector 1 is a reflector that reflects the light that has traveled from the object O along the viewing direction toward the obstacle S to the side in front of the obstacle S. The image propagation element 2 is an element arranged at the position where the light reflected by the first reflector 1 is incident. The second reflector 3 is a reflector that reflects the light from the image propagation element 2 and causes it to reach the viewing position V. Since FIG. 1 is a plan view, in this example, the viewing direction is horizontal. However, the viewing direction does not have to be horizontal; it can be an oblique direction or, in some cases, a vertical (perpendicular) direction. Therefore, FIG. 1 can also be understood as a schematic plan view seen in the plane to which the viewing direction belongs.

[0013] In FIG. 1, a circular shape is drawn as the shielding object S, and a cylindrical object is assumed as the shielding object S, but the shielding object S can be of various shapes. In this embodiment, a configuration is adopted in which light detour optical paths are formed symmetrically on both sides of the shielding object S. The detour optical paths are symmetrical. That is, two first reflectors 1, two image propagation elements 2, and two second reflectors 3 are provided respectively, forming symmetrical optical paths. Hereinafter, only the right side on the paper surface of FIG. 1 will be taken up for explanation.

[0014] As shown in FIG. 1, in this embodiment, a triangular prism is adopted as the first reflector 1. The triangular prism as the first reflector 1 is in the shape of a prism with a right-angled isosceles triangle cross-section and is long in the direction perpendicular to the paper surface of FIG. 1. The material is an optical glass such as BK7, but it may also be a resin such as an acrylic resin. This also applies to the second reflector 3. In the first reflector 1, one of the two surfaces 11 intersecting at a right angle of the first reflector 1 serves as the incident surface, and the first reflector 1 is arranged so that this incident surface 11 is perpendicular to the viewing direction. Therefore, the inclined surface 12 of the first reflector 1 forms an angle of 45 degrees with respect to the viewing direction. The surface 13 intersecting at a right angle to the incident surface 11 serves as the exit surface and is along the viewing direction. The light that has traveled from the object O to be shielded along the viewing direction enters the first reflector 1 from the incident surface 11, is reflected by the inclined surface 12, and exits laterally from the exit surface 13.

[0015] The image propagation element 2 significantly characterizes the occluded object visualization device of the embodiment. FIG. 2 is a schematic plan view showing the configuration and operation of the image propagation element 2 in the first embodiment. As shown in FIG. 2, the image propagation element 2 includes a first prism sheet 4 disposed in a region where light from the first reflector 1 is incident, a second prism sheet 5 disposed on the viewing position V side in the viewing direction with respect to the first prism sheet 4, and a propagation reflector 6. A prism sheet is an optical element formed by arranging a plurality of fine prism parts. In this embodiment, the first prism sheet 4, the second prism sheet 5, and the propagation reflector 6 are realized by a single plate-shaped member. That is, the plate-shaped member serves as the image propagation element 2. Each of the prism sheets 4 and 5 is formed with a thickness that is a part of the thickness of the image propagation element 2. Considering this part of the thickness, it can be said to be sheet-shaped, so it is called a prism sheet.

[0016] FIG. 3 is a schematic perspective view of the image propagation element 2. As shown in FIG. 3, one side surface of the plate-shaped image propagation element 2 is processed into a prism sheet shape, and the part including one side surface corresponds to the first prism sheet 4 and the second prism sheet 5. As shown in FIG. 3, the first and second prism sheets 4 and 5 are configured by arranging long and fine prism parts (hereinafter referred to as linear prism parts) 41 and 51 whose cross-sections are triangular and extend in a certain direction. The prism sheet is sometimes called a linear Fresnel. Each of the linear prism parts 41 and 51 is arranged parallel to each other and packed (without gaps). Such an image propagation element 2 is often formed of a translucent resin such as an acrylic resin and is often manufactured by molding such as hot pressing.

[0017] In the image propagation element 2 shown in FIG. 3, half of one side surface functions as the first prism sheet 4, and the other half of the surface functions as the second prism sheet 5. In the illustrated state shown in FIG. 2, in the image propagation element 2, the half closer to the occluded object O is the first prism sheet 4, and the half farther away is the second prism sheet 5. Hereinafter, boundary surface B is considered to be the optical reference surface. Boundary surface B is a surface perpendicular to the viewing direction, and is an imaginary surface that divides the incident side and the exit side of the hidden object visualization device. Boundary surface B is indicated by a dashed line in Figures 1 and 2. In the integrated prism sheet 7, the first prism sheet 4 is on the incident side of boundary surface B, and the second prism sheet 5 is on the exit side.

[0018] As shown in FIG. 2, in the first prism sheet 4 forming the right-side bypass optical path, the inclined surface (working surface) 411 of each linear prism portion 41 is formed on the output side so as to reflect light obliquely inward. The angle of the light output surface is θ a As shown in Fig. As shown in FIG. 2, the propagation reflector 6 is the other surface of the plate-shaped image propagation element. This surface is flat and serves as a total reflection surface along the viewing direction. Therefore, as shown in FIG. 2, the light that reaches the propagation reflector 6 and is reflected therefrom is directed toward the second prism sheet 5. Each inclined surface 411 of the first prism sheet 4 is at an angle at which the light reflected there reaches the propagation reflector 6 and is incident at an angle that satisfies the total reflection condition (an angle equal to or greater than the critical angle). For example, the angle θ of each inclined surface a is about 30 to 40°. In order to make one surface of the image propagation element 2 a total reflection surface and function as the propagation reflector 6, it is desirable to space the surface a little from the first reflector 1 and the second reflector 3. This is to make one medium air to generate a refractive index difference. It is desirable to have a short distance, preferably 0.1 to 0.5 mm. This is to make the structure compact and to further improve visibility through a position outside the shielding object, which will be described later.

[0019] The second prism sheet 5 has the inclined surfaces 511 facing in the opposite direction to that of the first prism sheet 4. That is, as shown in FIG. 2, the inclined surfaces 511 of each linear prism portion 51 in the second prism sheet 5 face obliquely inward on the incident side. More specifically, the angle of the inclined surfaces 511 of each linear prism portion 51 in the second prism sheet 5 (θ in FIG. 2) b(shown by) is the angle at which the reflected light travels in a direction parallel to the boundary surface B. Each inclined surface 411 in the first prism sheet 4 and each inclined surface 511 in the second prism sheet 5 can also be expressed as being line-symmetrical with respect to the boundary surface B. Since they are line-symmetrical, θ b = θ a is true.

[0020] Regarding the second reflector 3 as well, a prism-shaped one with a right-angled isosceles triangle cross-section is adopted, and it is also long in the direction perpendicular to the plane of the paper in FIG. 1. The second reflector 3 is arranged line-symmetrically with respect to the first reflector 1 with respect to the boundary surface B. Among the two surfaces that intersect at a right angle, the surface along the viewing direction is the incident surface 31, and the surface 33 perpendicular to the viewing direction is the exit surface. As shown in FIG. 1, the light that is reflected by each inclined surface of the second prism sheet 5 and travels in a direction perpendicular to the viewing direction enters the second reflector 3 from the incident eye and is reflected at a right angle by the inclined surface 32. Then, it travels in the viewing direction and exits from the exit surface 33.

[0021] Such a configuration and the arrangement of each element are the same for the detour circuit on the left side. The first reflector 1, the image propagation element 2, and the second reflector 3 that form the detour circuit on the left side have a configuration and arrangement that are line-symmetrical with respect to the elements that form the detour circuit on the right side with respect to a virtual plane perpendicular to the boundary line at the center of the boundary surface B. Therefore, further explanation is omitted. In addition, each element that forms a detour optical path on the left and right is held by a frame or holder (not shown) and is fixed in position. The frame or holder has a shape that does not block the light that travels through the detour optical path from the object to be shielded to the viewing position. Also, a spacer of an appropriate size is provided between the first and second reflectors 1 and 3 and the first and second prism sheets 4 and 5. By holding these elements in a state where the spacer is interposed, the above-mentioned separation distance is ensured.

[0022] The operation of the occluded object visualization device according to such an embodiment will be described below. The occluded object O reflects light received from sunlight, indoor illumination light, or the like. In some cases, the occluded object O itself may be a light source. The light from the occluded object O enters the first reflector 1 of the occluded object visualization device according to the embodiment. The incident light is reflected by the inclined surface 12, split left and right, and travels laterally. Then, it bypasses the shield S while passing through the left and right image propagation elements 2. That is, it passes through the propagation reflector 6 and reaches each inclined surface 411 of the first prism sheet 4, is reflected by each inclined surface 411, and heads towards the inner propagation reflector 6. Then, it is reflected by the propagation reflector 6 and heads towards the second prism sheet 5, reaching each inclined surface 511 of the second prism sheet 5. Further, the light reflected by each inclined surface 511 passes through the propagation reflector 6 and heads towards the inner second reflector 3. Such an operation is performed symmetrically with respect to the left and right image propagation elements 2.

[0023] The light reflected by each inclined surface 511 of the left and right second prism sheets 5 travels inward, enters each second reflector 3, is reflected by each inclined surface 32, and heads towards the viewing position V. Then, at the viewing position V, this light is captured, and the occluded object O is visually recognized. For example, when the shield S is a front pillar in an automobile, the light is captured by the eyes of the driver sitting in the driver's seat, and the occluded object O is visually recognized. In the above operation, when the light reflected by the first reflector 1 reaches the first prism sheet 4, an image of the occluded object O is projected onto the first prism sheet 4. However, the first prism sheet 4 reflects the light at each inclined surface 411 and causes it to reach the second prism sheet 5 through the propagation reflector 6. This state is such that the image has shifted (propagated) from the first prism sheet 4 to the second prism sheet 5.

[0024] According to the occluded object visualization device of such an embodiment, the detour optical path of the light advancing toward the shielding object S includes the image propagation element 2, and the image propagation element 2 includes the prism sheets 4 and 5 and the propagation reflector 6 to propagate the image, so that the detour optical path can be made compact, and the structure does not protrude greatly laterally for the visualization of the occluded object O. Note that the light rays indicated by solid lines in FIG. 1 are representative light rays, and actually, the light rays that travel slightly obliquely with respect to the viewing direction also reach the viewing position V through the above detour optical path.

[0025] In the occluded object visualization device of the first embodiment, the images (visualization images) of the occluded object O at the viewing position V are reversed left and right in each detour optical path. This point will be described with reference to FIG. 4. FIG. 4 is a schematic diagram showing the inversion of the image in the occluded object visualization device of the first embodiment. In FIG. 4, for the sake of understanding, it is assumed that the occluded object O is a square panel on which the characters a, i, u, and e are printed in this order and arranged horizontally side by side. When the light from this occluded object O reaches the viewing position V through the occluded object visualization device, an image as shown in FIG. 4 is viewed. As shown here, the image at the viewing position V is projected on the left side with the left half of the occluded object O inverted left and right, and projected on the right side with the right half of the occluded object O inverted left and right. Due to such inversion of the image, the occluded object visualization device of the first embodiment is suitably used for applications where the inversion of the image does not cause problems. For example, it is suitably used when it is only necessary to determine the presence of an object, such as when the other side of a corner cannot be seen, or when the occluded object O is uniform and there is no problem even if it is inverted.

[0026] Note that in the configuration of the above embodiment, when it is difficult to utilize the total reflection condition in the propagation reflector 6, the propagation reflector 6 may be a half mirror. A half mirror is a mirror that transmits half of the light and reflects the other half.

[0027] Next, the obscured object visualization device of the second embodiment will be described. FIG. 5 is a schematic plan view of the main part of the obscured object visualization device of the second embodiment. The configuration of the image propagation element 2 of the obscured object visualization device of the second embodiment is different from that of the first embodiment. In the first embodiment, the angle θ of each inclined surface 411 in the first prism sheet 4 a is uniform, and the angle θ of each inclined surface 511 in the second prism sheet 5 b is uniform. In the second embodiment, the angles of the inclined surfaces 411 of the first prism sheet 4 are not uniform, and the angles of the inclined surfaces 511 in the second prism sheet 5 are not uniform.

[0028] Thus, in the obscured object visualization device of the second embodiment, the angles of the inclined surfaces 411 and 511 of the prism sheets 4 and 5 are made non-uniform in order to eliminate the image inversion that occurred in the obscured object visualization device of the first embodiment. More specifically, in the second embodiment, the angle of each inclined surface 411 in the first prism sheet 4 increases as it moves away from the boundary surface B. That is, in order from the closest to the boundary surface B, θ a1 , θ a2 , θ a3 , ··· θ an , if we set them like this, then θ a1 < θ a2 < θ a3 ··· < θ anIt is thus configured. For this reason, as shown in FIG. 5, the light reflected by the inclined surface 411 of the linear prism portion 41 at the position closest to the boundary surface B of the first prism sheet 4 reaches the inclined surface 511 of the linear prism portion 51 at the position closest to the boundary surface B of the second prism sheet 5 via the propagation reflector 6. The light reflected by the inclined surface 411 of the linear prism portion 41 that is second closest to the boundary surface B reaches the inclined surface 511 of the linear prism portion 51 that is second closest to the boundary surface B in the second prism sheet 5. The light reflected by the inclined surface 411 of the linear prism portion 41 that is third closest to the boundary surface B reaches the inclined surface 511 of the linear prism portion 51 that is third closest to the boundary surface B in the second prism sheet 5, ···, and the light reflected by the inclined surface 411 of the linear prism portion 41 that is farthest from the boundary surface B reaches the inclined surface 511 of the linear prism portion 51 that is farthest from the boundary surface B in the second prism sheet 5.

[0029] The angles of the inclined surfaces 511 of the respective linear prism portions 51 in the second prism sheet 5 increase as they are farther from the boundary surface B, similar to the first prism sheet 4. That is, in order from closest to the boundary surface B, θ b1 , θ b2 , θ b3 , ··· θ bn If we set them as such, then θ b1 < θ b2 < θ b3 ··· < θ bn is the case. And in the first and second prism sheets 4 and 5, the linear prism portions 41 and 51 at positions with the same distance from the boundary surface B have the same angles of the inclined surfaces 411 and 511. That is, θ a1 = θ b1 , and θ a2 = θ b2 , and θ a3 = θ b3 , ···, and θ an = θ bn is the case. Due to such a positional relationship and a gradual change in the inclined surface angle, as shown in FIG. 5, the light that reaches each linear prism portion 51 of the second prism sheet 5 is reflected by each inclined surface 511 and heads inward, and is reflected by the second reflector 3 as in the first embodiment and heads toward the viewing position V.

[0030] In the second embodiment, since the image propagation element 2 has the above-described configuration, the image inversion that occurred in the first embodiment is eliminated. This point is shown in FIG. 6. FIG. 6 is a schematic diagram showing the elimination of image inversion in the second embodiment. As shown in FIG. 6(2), according to the second embodiment, the image formed by the detour optical path on the left side is not inverted as a whole, and the image formed by the detour optical path on the right side is also not inverted as a whole.

[0031] However, strictly speaking, in units of each one corresponding linear prism portion 41, 51 in the first and second prism sheets 4, 5, the image is inverted. Therefore, it is preferable that the pitch (the width in the arrangement direction, indicated by p in FIG. 5) of the linear prism portions 41, 51 is not increased. When p increases, the inversion of the image in units of the linear prism portions 41, 51 (hereinafter referred to as prism unit image inversion) becomes visible. Therefore, it is preferable that the pitch p is less than the width at which the prism unit image inversion is visible to the human eye at the viewing position. By doing so, the object O to be shielded is viewed without a sense of incongruity. Specifically showing the dimensions, the pitch p is preferably 5 mm or less, and more preferably 1 mm or less. In addition, whether the prism unit image inversion is visible also depends on the width of the entire image. The width of the entire image is the width of the first and second prism sheets 4, 5. When the width (the length in the viewing direction in this embodiment) of each prism sheet 4, 5 is wide, even if the pitch p is somewhat large, the prism unit image inversion of the linear prism portions 41, 51 is difficult to be seen. When the width of each prism sheet 4, 5 becomes narrow, if the width of the linear prism portions 41, 51 is not narrowed accordingly, the prism unit image inversion becomes easy to be seen. Considering these, it is preferable that the pitch p is 10% or less with respect to the width of each prism sheet 4, 5 (the average width when the widths are different). Also, if the pitch p is too small, the influence of diffraction appears and it becomes difficult to clearly visually recognize the image. Therefore, the pitch p is preferably set to a size such that the influence of diffraction does not appear during visual recognition. Specifically, the pitch p is preferably 10 μm or more.

[0032] As can be understood from FIG. 5, in the configuration of the second embodiment, the propagation reflector 6 only needs to have a reflecting action only in a very limited region near the boundary surface B. For this reason, the propagation reflector 6 may be configured such that a reflective film is formed only in a limited region near the boundary surface B. Even when the propagation reflector 6 is a half mirror, there may be a configuration in which only a limited region near the boundary surface B is a half mirror and the rest is a transmissive portion (not a half mirror). Furthermore, a reflector having a short length in the visual recognition direction may be employed as the propagation reflector 6.

[0033] In the first and second embodiments, each inclined surface 41, 51 of the first and second prism sheets 4, 5 may be appropriately configured as a half mirror. This will be described with reference to FIG. 1. In FIG. 1, when a person visually recognizes the object O to be shielded at the visual recognition position V, for example, the person may shift the line of sight slightly from the visual recognition direction and look at a little beside the shield S. In this case, since the second prism sheet 5 is located in the line of sight direction, the second prism sheet 5 may become the shield S. That is, the second prism sheet 5 may block the light traveling toward the visual recognition position V through the position outside the shield S (indicated by a two-dot chain line in FIG. 1). For the first and second prism sheets 4, 5, it is preferable in terms of efficiency to provide a reflective film on each inclined surface 411, 511 to make it a completely reflective surface, but it is desirable not to block the light from the position outside the shield S. Therefore, at least for the non-acting surface of the second prism sheet 5, it is made a half mirror so as not to block the light from the position outside the shield S. Depending on the orientation, there may be cases where the light is not blocked even without being a half mirror, so it may be a normal optical surface.

[0034] When the inclined surfaces 511 of the second prism sheet 5 are made into normal mirrors (total reflection mirrors) instead of half mirrors, depending on the line of sight and the angles of the inclined surfaces 511, they may be blocked in some cases. However, compared with the prior art, the lateral protrusion is smaller, so the area that cannot be visually recognized is small, and there are many cases where there is no problem. For the inclined surfaces 411 of the first prism sheet 4, when they are blocked by the shielding object S and cannot be originally seen from the visual position V, there is no problem even if they are made into normal mirrors.

[0035] When total reflection is to be achieved for the inclined surfaces 411 and 511 of the prism sheets 4 and 5, a reflective film such as an aluminum vapor deposition film is formed. Depending on the material (refractive index) of the prism sheets 41 and 51 and the angles of the inclined surfaces 411 and 511, there may be cases where the conditions for total reflection are met and there is no particular need to provide a reflective film. In addition, instead of adopting the half-lammy configuration, a polarization control configuration may be adopted. For example, P-polarized light is reflected to visualize the shielded object O, and S-polarized light is transmitted to enable visual recognition through the position outside the shielding object S (the reverse is also possible).

[0036] In the shielded object visualization device of each of the above embodiments, the optical paths bypassing the shielding object S are formed on both sides of the shielding object S, but it may also be on one side. A preferred application example in which a bypass optical path is formed only on one side will be described below. FIG. 7 is a schematic plan view showing a preferred application example of a third embodiment in which a bypass optical path is formed only on one side. The shielded object visualization device of the third embodiment shown in FIG. 7 is a device preferably adopted to eliminate the lack of safety due to the inability to see the other side due to a shielding object S such as a corner of a sidewalk (for example, a corner of a building wall). As shown in FIG. 7, the shielded object visualization device of this embodiment is installed so as to straddle from the outer surface on the other side to the front surface of the outer wall W of the building and turn around the corner. The first reflector 1 is fixed to the outer wall surface on the other side. The second reflector 3 is fixed to the outer wall surface on the front side. The image propagation element 2 is fixed in a state of being in contact with the corner of the outer wall W.

[0037] Also in this embodiment, the light incident on the first reflector 1 is reflected laterally and travels toward the image propagation element 2. Then, in the image propagation element 2, the image is propagated by the first and second prism sheets 4 and 5 and the propagation reflector 6, and the light is emitted from the second prism sheet 5 toward the second reflector 3. This light is reflected by the second reflector 3 and is visually recognized by the pedestrian in the front. Therefore, a pedestrian in the front can visually recognize a person walking on the other side of the corner and heading toward the corner, and it is possible to prevent a collision at the corner.

[0038] In each of the above embodiments, the configuration is such that only one set of the first reflector 1, the image propagation element 2, and the second reflector 3 is provided, but a configuration in which two or more sets are vertically arranged may be used. Such an embodiment will be described below. FIG. 8 is a schematic plan sectional view showing a fourth embodiment in which a plurality of sets of the first and second prism sheets 4 and 5 and the propagation reflector 6 are vertically arranged. As shown in FIG. 8, in the fourth embodiment, the next set of the first reflector 1 is arranged at the position where the light emitted from the second reflector 3 of the first set is incident, and the image is further propagated by the image propagation element 2 so that the light is emitted from the second reflector 3 to the visual recognition position V.

[0039] The shield visual recognition device of the fourth embodiment is preferably adopted when the shield S is long in the visual recognition direction. Also, when the vertical arrangement configuration as in the fourth embodiment is adopted for the first embodiment, there is an advantage that the inversion of the image is eliminated. The image is inverted in the first set, but is further inverted in the next set, so that the image is visually recognized at the visual recognition position V in the state where it has returned to the original state and is not inverted. To obtain such an effect, it is sufficient to provide an even number of sets of the first reflector 1, the image propagation element 2, and the second reflector 3. In the second embodiment, since the image inversion is prevented in the set of only one first reflector 1, the image propagation element 2, and the second reflector 3, the device does not become long in the visual recognition direction, and in this respect, the device of the second embodiment has an advantage of making the structure around the shield S compact.

[0040] Also, in the fourth embodiment, it is not essential that each image propagation element 2 in the plurality of sets of first reflectors 1, image propagation elements 2, and second reflectors 3 be arranged on the same plane, and they may be arranged on a bent (non-planar) plane. That the image propagation element 2 is provided on a bent plane means that the propagation reflector 6 in the first set of image propagation elements 2 and the propagation reflector 6 in the next set of image propagation elements 2 are not flush. Hereinafter, a fifth embodiment having such a configuration will be described. FIG. 9 is a schematic plan view of the shielded object visualization device according to the fifth embodiment. Hereinafter, for convenience of explanation, the plane on which the reflecting surface of the propagation reflector 6 is located is called the propagation plane.

[0041] As shown in FIG. 9, when the propagation plane in the first set and the propagation plane in the next set are not flush, the angle of the reflecting surface of the second reflector 3 in the first set or the reflector of the first reflector 1 in the next set is appropriately adjusted. In the example of FIG. 9, the angle of the reflecting surface of the first reflector 1 in the next set is adjusted. That is, the reflecting surface of the first reflector 1 in the next set is adjusted so that when the light that has been reflected at a right angle by the reflecting surface of the second reflector 3 in the first set is reflected, it travels perpendicular to the propagation plane in the next set. Usually, the posture of the first reflector 1 is changed to adjust the angle of the reflecting surface.

[0042] A configuration in which a plurality of sets of first reflectors 1, image propagation elements 2, and second reflectors 3 are provided in a state where such a propagation surface is bent can be suitably applied to various applications. For example, it is suitably applied to a motorcycle helmet. The first set of first reflectors 1 is fixed to the rear part of the helmet to take in light, and each set is arranged vertically along the circumferential surface of the helmet. Then, the second reflector 3 of the last set is arranged in front of the helmet so that the light reflected and advancing can be visually recognized by the wearer (motorcycle driver). By doing so, the situation behind can be visually recognized even while looking ahead, which greatly helps to improve safety. The second reflector 3 of the last set functions like a screen that reflects the situation behind, but it is preferably positioned at the corner position in the front field of view so as not to significantly block the front field of view. Incidentally, each set of image propagation elements 2, etc. may be arranged along the inner surface of the helmet or may be arranged within the thickness of the helmet.

[0043] As another example similar to the above, an obscured object visualization device having a configuration of a bent propagation surface can also be applied to VR (virtual reality) goggles. When it is desired to visually recognize the situation behind in the same way as a helmet, the first set of first reflectors 1 is fixed at a position located at the back of the head when the goggle band is worn, and each set of image propagation elements 2, etc. is fixed along the band. Then, the second reflector 3 of the last set is provided inside the goggle body, and the emitted light is captured by an image sensor such as a CCD and superimposed on the VR image so that an image of the situation behind is displayed. There may also be a configuration in which the front situation can be visually recognized. In this case, the first set of first reflectors 1 is provided at any location on the front surface of the goggle body to take in light from the front, and each set of image propagation elements 2, etc. is arranged along the bent propagation surface. Then, the light from the second reflector 3 of the last set is captured by the image sensor, visualized, and superimposed on the VR image for display. In either case, there may also be a configuration in which it is not superimposed for display but switched for display. That is, there may also be a configuration in which the VR image is stopped and a real image of the rear or front is displayed. According to these configurations, it is suitable because a real image of the rear or front can be visually recognized while wearing the VR goggles.

[0044] Furthermore, the occluded object visualization device of each embodiment can also be used for the purpose of landscape improvement. That is, since the shield S spoils the landscape, it is for the purpose of visualizing the occluded object O so that the shield S seems not to exist. For example, against the backdrop of frequent major earthquakes in recent years, the demand for seismic strengthening of buildings is remarkable. In order to strengthen seismic resistance, it is often done to add and reinforce beams, columns, etc. However, there is a problem that such reinforcing structural materials are visible from indoors and spoil the landscape seen from the window. In such a case, the occluded object visualization device of any of the embodiments can be arranged so that the outdoor scenery can be visually recognized indoors without being blocked by the reinforcing structural materials.

[0045] As another example regarding buildings, an example of application to a stadium where various sports are held can be cited. In various stadiums, in some cases, columns are provided in the stands to support structures such as roofs. In this case, the play on the ground may be blocked by the columns and not visible. In order to solve such a problem, the occluded object visualization device of any of the above embodiments can be arranged.

[0046] In each of the above embodiments, the first and second reflectors 1 and 3 are triangular prisms that are long in a direction perpendicular to the plane in which the detoured optical path is formed, but there may be other configurations. For example, it may be a flat plate-shaped reflecting mirror that is long in a direction perpendicular to the plane of the detoured optical path. In this case, a holder for holding the reflecting mirror is provided so as to be at an angle of 45 degrees with respect to the visual recognition direction. However, when a triangular prism-shaped one is adopted as the reflectors 1 and 3, it can also be used as a structure for holding the first and second prism sheets 4 and 5, so it is preferable.

[0047] In the configuration of each embodiment, the first and second prism sheets 4 and 5 are composed of linear prism portions 41 and 51, but there may also be a case of a prism sheet in which short prism portions are arranged instead of long prism portions. In FIG. 1, when the length of the shield S in the direction perpendicular to the paper surface is not long, a prism sheet in which short prism portions are arranged can be adopted as the first and second prism sheets.

[0048] The first and second prism sheets 4 and 5 are part of the plate-shaped image propagation element 2 and are integrated with the propagation reflector 6, but they may also be separate members. That is, the first and second prism sheets 4 and 5 may be manufactured as an integrated sheet-like member, and a flat plate-shaped member may be provided separately as the propagation reflector. Furthermore, the first and second prism sheets 4 and 5 may also be manufactured and arranged as separate members. In this case, the first prism sheet and the second prism sheet may be in contact with each other or may be separated. Note that when the first and second prism sheets are provided as separate members from the propagation reflector, each prism sheet is configured such that each prism portion is provided on a sheet-like base material portion.

[0049] Also, in each of the above embodiments, refractive types may be adopted for the first and second prism sheets 4 and 5. That is, the first prism sheet 4 may refract light at the inclined surface 411 and direct it toward the propagation reflector 6, and the second prism sheet 5 may refract light from the propagation reflector 6 at the inclined surface 511 and direct it toward the second reflector 3. However, when the first and second prism sheets 4 and 5 are of the refractive type, since the propagation reflector 6 is arranged as another element outside thereof, it will structurally protrude laterally. Therefore, in terms of compactness, it is preferable that the first and second prism sheets 4 and 5 be of the reflective type.

Explanation of Reference Numerals

[0050] 1 First reflector 2 Image propagation element 3 Second reflector 4 First prism sheet 41 Linear prism portion 411 Inclined surface 5 Second prism sheet 51 Linear prism portion 511 Inclined surface

Claims

1. An apparatus for visualizing an object to be shielded, which is located on the far side of a shield and shielded by the shield, at a visible position in front of the shield, comprising: a first reflector that reflects light traveling from the object to be shielded along the viewing direction towards the shield laterally in front of the shield when the direction connecting the position of the shield and the visible position is defined as the viewing direction; an image propagation element disposed at the position where the light reflected by the first reflector is incident; a second reflector that reflects the light from the image propagation element to reach the visible position; wherein the image propagation element includes a first prism sheet disposed in a region where the light from the first reflector is incident, a second prism sheet disposed on the visible position side in the viewing direction with respect to the first prism sheet, and a propagation reflector; each prism sheet is an element in which a plurality of prism portions are arranged; each prism portion of the first prism sheet propagates an image formed by the light from the first reflector to the second prism sheet, directs the light from the first reflector to the propagation reflector, and reflects the light by the propagation reflector to reach the second prism sheet; the second reflector reflects the light from the second prism sheet to travel in the viewing direction and reach the visible position, making the propagated image visible at the visible position.

2. The apparatus for visualizing an object to be shielded according to claim 1, wherein each prism portion of the first prism sheet is formed with an inclined surface such that when the image is propagated by the light reflected by the propagation reflector reaching the second prism sheet, the image in the second prism sheet becomes an inverted image sandwiching the boundary surface between the first and second prism sheets perpendicular to the viewing direction.

3. The apparatus for visualizing an object to be shielded according to claim 2, wherein the inclined surface of each prism portion of the first prism sheet is a surface that reflects light to reach the propagation reflector, and the inclined surface of each prism portion of the second prism sheet is a surface that reflects light to reach the second reflector, and the angles of the inclined surfaces of each prism portion of the first prism sheet and each prism portion of the second prism sheet with respect to the viewing direction increase as they move away from the boundary surface.

4. The first and second prism sheets have the respective prism portions arranged along the viewing direction, and a width of each of the prism portions in the viewing direction is less than a width at which inversion of an image in a unit of each of the prism portions is visually recognized by a human eye. The obscured object visualization device according to claim 2, characterized in that.

5. The image propagation element is an element that transmits light from a position outside the obscured object toward a viewing position. The obscured object visualization device according to any one of claims 1 to 4, characterized in that.

Images