AIR FLOATING VIDEO INFORMATION DISPLAY SYSTEM

A video is suitably displayed outside a space. The present invention contributes to the following sustainable development goals: “3. Good health and well-being”; “9. Industry, innovation and infrastructure”; and “11. Sustainable cities and communities”. This air floating video display system includes: a display panel for displaying images; a light source apparatus for supplying light to the display panel; and a retroreflector that reflects image light from the display panel and that causes the air floating video to be displayed as a real image in air by using the reflected light.

TECHNICAL FIELD

The present invention relates to an air floating video information display system and an optical system used therefor.

BACKGROUND ART

As an air floating video information display system, a video display apparatus that directly displays a video toward the outside and a display method in which the video is displayed as a space screen have already been known. Further, a detection system that reduces erroneous detection for an operation on an operation surface of a displayed space image has also been disclosed in, for example, Patent Document 1.

RELATED ART DOCUMENTS

Patent Documents

SUMMARY OF THE INVENTION

Problems to be Solved by the Invention

As an air floating video information display system, a video display apparatus that directly displays a video toward the outside and a display method in which the video is displayed as a space screen have already been known. However, in the above-described conventional air floating video information display system, means for preventing a malfunction occurring when external light is incident on a retroreflector that generates an air floating video and a technique for optimizing a design including a light source of a video display apparatus as a video source of the air floating video have not been considered.

An object of the present invention is to provide, in an air floating information display system or an air floating video display apparatus, a technique capable of displaying an air floating video having a high visibility (apparent resolution and contrast) and subjected to a reduced influence of external light and capable of displaying a favorable video.

Means for Solving the Problems

In order to solve the above-described problems, configurations described in the claims, for example, are adopted. Although the present application includes a plurality of means for solving the above-described problems, an air floating video information display apparatus as an example thereof is given below. An air floating video information display system as an example of the present application includes a display panel that displays a video, a light source apparatus that supplies light to the display panel, and a retroreflector that reflects an air floating video as a real image in air by the reflected light.

Effects of the Invention

According to the present invention, air floating video information can be favorably displayed without the image quality of an air floating video decreasing even if external light is incident. Problems, configurations, and effects other than the foregoing will be made apparent from the following description of an embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to contents of the embodiment (hereinafter also referred to as “present disclosure”) described below. The present invention also covers the spirit of the invention, the scope of the technical idea described in the claims, or equivalents thereof. Further, configurations of the embodiment (examples) described below are only illustrative, and various changes and modifications can be made by those skilled in the art within the scope of the technical idea disclosed in the present specification.

Further, in the drawings for describing the present invention, components having the same or similar functions are respectively denoted by the same reference signs, and different names are respectively appropriately used therefor. On the other hand, repetitive description of the functions and the like may be omitted. Note that in the following description of an embodiment, a video floating in a space is expressed as a term “air floating video”. Instead, this term may be expressed as “aerial image”, “space image”, “aerial floating video”, “air floating optical image of a display image”, “aerial floating optical image of a display image”, or the like. The term “air floating video” mainly used in the description of the embodiment is used as a typical example of these terms.

The present disclosure relates to an information display system capable of transmitting a video based on video light from a video light emission source having a large area through a transparent member that partitions a space such as a show window glass and displaying the video as an air floating video inside or outside a store (space). Further, the present disclosure relates to a large-scale digital signage system configured using a plurality of such information display systems.

According to the following embodiment, high-resolution video information can be displayed above a glass surface of a show window or a light-transmittable plate material while floating in air, for example. At this time, only regularly reflected light can be efficiently reflected with respect to a retroreflector by making a divergence angle of video light to be emitted small, i.e., an acute angle and equalizing the video light to have a specific polarized wave. This results in a high light utilization efficiency, makes it possible to suppress a ghost image, which has been a problem in a conventional retroreflection system, to be generated in addition to a main air floating image, and makes it possible to obtain a clear air floating video.

Further, an apparatus including the light source in the present disclosure makes it possible to provide an air floating video information display system capable of significantly reducing power consumption and being new and excellent in availability. Further, a technique of the present disclosure makes it possible to provide a floating video information display system vehicle capable of displaying a so-called unidirectional air floating video that is visually recognizable outside a vehicle through a shield glass including a windshield, a rear window, and a side window.

On the other hand, in a conventional air floating video information display system, an organic EL panel or a liquid crystal display panel (a liquid crystal panel or a display panel) is combined with a retroreflector as a high-resolution color display video source. In a first retroreflector2used in the air floating video display apparatus according to the conventional technique, video light is diffused at a wide angle. Accordingly, besides reflected light to be regularly reflected by the retroreflector that is a first example composed of a polyhedron illustrated inFIG.3since a shape used for a retroreflector2aas illustrated inFIG.3is a polyhedron, six ghost images including ghost images respectively indicated by signs3aand3fare generated by video light to be obliquely incident, which deteriorating the image quality of an air floating video. Further, the same air floating video as the ghost image is also viewed by a person other than a viewing person, thereby also presenting a large problem from a viewpoint of security.

Further, in a second retroreflector5used in an air floating video display apparatus, a first light control panel221and a second light control panel222are formed by vertically arranging optical members20with a constant pitch each having a large number of and strip-shaped planar light reflection portions side by side on respective surfaces on one side of transparent flat plates18and17each having a predetermined thickness as illustrated inFIG.1(A). Here, the light reflection portions of the optical members20respectively constituting the first light control panel221and the second light control panel222are arranged to intersect each other (in an orthogonal state in this example) in a plain view.

Then, a function of the second retroreflector used in the air floating video display apparatus and specific examples of the air floating video display apparatus will be described. As illustrated inFIG.1(B), the second retroreflector5is generally arranged to be inclined at an angle of 40 to 50 degrees with respect to the video display apparatus1. At this time, video light is emitted from the second retroreflector5to an air floating video3at the same angle as an angle at which it is incident on the second retroreflector5. At this time, the air floating video is formed at a symmetric position spaced by the same distance as a distance L1between the video display apparatus1and the second retroreflector5.

Hereinafter, a mechanism for forming an air floating video will be described in detail with reference toFIGS.1and2. Video light emitted from the video display apparatus1provided on one side of the second retroreflector5is reflected by a planar light reflection portion C (a reflection surface of a light reflector20) in the second light control member222, and is then reflected by a planar light reflection portion C′ (a reflection surface of the light reflector20) in the first light control member221to form the air floating image3(a real image) at a position outside the second retroreflector5(a space on the other side). That is, the second retroreflector5is used, thereby establishing an air floating video information apparatus. In the space, an image of the video display apparatus1can be displayed as an air floating image.

In the second retroreflector5described above, the two reflection surfaces exist, as described above. Accordingly, two ghost images3aand3bcorresponding to the number of reflection surfaces are generated besides to the air floating image3as illustrated inFIGS.2A and2B.

Furthermore, if the intensity of external light is high, a distance (300 μm or less) between the reflection surfaces is shortened when the external light is incident from an upper surface of the second retroreflector5. Accordingly, it has been found out that there are such harmful effects that a light interference occurs, iridescently reflected light is observed, and the viewing person recognizes the existence of the retroreflector. An area in which interference light to be generated by a pitch of the reflection surfaces in the retroreflector5by the incidence of the external light is experimentally found by a measurement environment illustrated inFIG.4using an angle of incidence of the external light as a parameter such that the interference light does not return to the viewing person. Obtained results are illustrated inFIG.5. It has been found out that when the pitch of the reflection surfaces is 300 μm and the height of each of the reflection surfaces is 300 μm, the interference light does not return toward the viewing person if the retroreflector is inclined by an angle of inclination OYz of 35 degrees or more.

On the other hand, it has been found out that at a ratio (H/P) of a pitch P of the light reflector20and a height H of the reflection surface thereof, described above, about 60% of the reflection surface forms an air floating image by retroreflection and remaining 40% is extraordinarily reflected light for generating a ghost image. Hereinafter, it is essential to shorten the pitch of the reflection surfaces to improve the resolution of the air floating video. In addition, it is necessary to make the height of the reflection surface higher than that at present to suppress the generation of the ghost image. However, as the ratio (H/P) of the pitch P and the height H of the reflection surfaces, a range from 0.8 to 1.2 may be selected with respect to 1.0 at present due to a manufacturing contrast of the second retroreflector5.

As a result of the above-described study, the inventors have studied a retroreflection optical system that implements an increase in the image quality of an air floating video obtained in an air floating video information display system using a second retroreflector in which an amount of generation of ghost images is, in principle, small, leading to the invention of the present application. Description will be made in detail below with reference to the drawings.

<First Configuration Example of Retroreflection Optical System Forming Air floating video Information Display System>

FIGS.6A to6Care diagrams each illustrating an example of a form of the retroreflection optical system used to implement the air floating video information display system according to the present disclosure. Further,FIGS.6A to6Care diagrams each illustrating an entire configuration of the air floating video information display system in the present embodiment. Referring toFIGS.6A to6Cwith the air floating video information display system (hereinafter also referred to as “present system”) according to the present disclosure, for example, an air floating video is looked down at an angle θ6 when the air floating video information display system is arranged on a desk for a viewing person of the air floating video. At this time, it has been found out that such an arrangement that an angle (an image forming position) of the air floating image is substantially equal to a sum (θ2+θ1) of an angle θ2 formed between a display surface of the video display apparatus1and the retroreflector5and an angle θ1 formed between the retroreflector5and the air floating image3, that is, an angle formed between a liquid crystal display panel11and the air floating video3is θ1+θ2 is an arrangement optimal to view the air floating video. Further,FIG.6Aillustrates an example in which a video light control sheet334is arranged on a front surface of the liquid crystal display panel11. The video light control sheet334illustrated inFIGS.6A to6Cmay be arranged between the liquid crystal display panel11and the retroreflector5, or may be arranged on the opposite side to the liquid crystal display panel with respect to the retroreflector5. That is, in order to erase a ghost image to be generated at this time to obtain a high-quality air floating video3, the video light control sheet334is provided on the emission side of the liquid crystal display panel11so that a diffusion property in an unnecessary direction can be controlled. Note that the video light control sheet334illustrated inFIGS.6A to6Cmay be expressed as a diffusion property control sheet.

As described above, the air floating video is formed at a position symmetric to the video display apparatus1with respect to the second retroreflector5, so that the angles θ1 and θ2 formed at their respective arrangements are equal to each other. Accordingly, if the angle θ6 at which the viewing person looks down the air floating video display system is determined, the video display apparatus1and the second retroreflector5may be arranged as the angle θ2=θ6/2 in the retroreflection optical system. Furthermore, a predetermined distance L1is required to increase the cooling efficiency of the video display apparatus1between the video display apparatus1and the second retroreflector5. Furthermore, a distance L2relative to L1needs to be determined to structurally obtain the above-described angle θ2.

The configuration of the air floating video information display system according to the present disclosure will be more specifically described. As illustrated inFIG.6A, there are provided the video display apparatus1that diffuses video light with a specific polarized wave at a narrow angle and the second retroreflector5. The video display apparatus1includes the liquid crystal display panel (hereinafter merely referred to as the liquid crystal panel)11and a light source apparatus13that generates light with a specific polarized wave having a narrow-angle diffusion property.

The video light with a specific polarized wave from the video display apparatus1is selectively transmitted by providing a surface, which contacts the outside of an apparatus (not illustrated), of the second retroreflector5with an absorption-type light polarization sheet101having an antireflection film provided on its front surface to prevent light reflected by a front surface of the second retroreflector5from affecting an air floating video obtained by absorbing another polarized wave included in external light.

Here, the absorption-type light polarization sheet101that selectively transmits the video light with a specific polarized wave has a property of transmitting the video light with a specific polarized wave. Accordingly, the video light with a specific polarized wave is transmitted by the absorption-type light polarization sheet101. The air floating video3is formed at a position symmetric with respect to the retroreflector5by the transmitted video light.

Note that light forming the aerial floating video3is an aggregation of light rays converging on an optical image of the aerial floating video3from the retroreflector5, and the light rays travel straight even after passing through the optical image of the aerial floating video3. Accordingly, the aerial floating video3is an image having a high directionality unlike diffused video light formed on a screen by a general projector or the like.

Therefore, in the configuration illustrated inFIG.6A, the aerial floating video3is visually recognized as a bright video when visually recognized by a user in a direction illustrated in the drawing. However, the aerial floating video3cannot be visually recognized at all as a video when visually recognized by another person in an up-down direction and a front-rear direction of a plane of paper. This property is very preferable when used for a system that displays a video requiring a high security and a video having a high secret level that is desired to be kept secret from a person who faces the user.

Note that light polarization axes of video light after reflection may be unequal depending on a performance of the retroreflector5. In this case, a part of the video light, the light polarization axes of which are unequal is absorbed by the above-described absorption-type light polarization sheet101. Accordingly, unnecessary reflected light is not generated in the retroreflective optical system, thereby making it possible to prevent or suppress a reduction in the image quality of the air floating image.

Further, in the air floating video display apparatus using the retroreflective optical system according to the present disclosure, even when the viewing person looks into the air floating video, a display screen of the video display apparatus1is light-shielded by a reflection surface of the retroreflector5. Accordingly, a display image of the video display apparatus1is more difficult to view than that when the video display apparatus1and the retroreflector oppose each other.

As illustrated inFIGS.6A to6C, light from the light source apparatus13having a narrow divergence angle described below is incident on the liquid crystal display panel11to generate a video luminous flux having a narrow divergence angle and make the video luminous flux incident on the retroreflector5, thereby obtaining the air floating image3. The air floating video3is formed at a position symmetric to the video display apparatus1with the retroreflector5used as a plane of symmetry. In order to erase ghost images to be respectively generated on both sides of the air floating video3(a regular image) to be originally formed to obtain a high-quality air floating video3at this time, the video light control sheet334is provided on the emission side of the liquid crystal display panel11so that a diffusion property in an unnecessary direction may be controlled.

A view/light path control film (VCF) manufactured by Shin-Etsu Polymer Co., Ltd., for example, is suitable as the above-described video light control sheet334, and its structure is a sandwich structure obtained by alternately arranging transparent silicone and black silicone and arranging synthetic resin on a light incidence/emission surface. When the above-described video light control sheet334is provided on the emission side of the liquid crystal display panel11, ghost images to be generated on both sides of the air floating video3due to unnecessary light can be erased. For a specific structure of the video light control sheet334, when a light shielding layer is provided on a vertical surface of the video light control sheet334, unnecessary light can be prevented from being generated, as illustrated inFIGS.12(A) and12(B). Furthermore, when antireflection films are respectively provided on video light incidence and emission surfaces of the video light control sheet334, unnecessary light is prevented from being generated, thereby making it possible to obtain a good property.

Further, a place where the above-described video light control sheet334is arranged may be the front surface of the retroreflector5, i.e., a surface on the side on which the air floating image3is formed as illustrated inFIG.6B. As a result, when the video light control sheet334is provided on the front surface of the retroreflector5, ghost images to be respectively generated on both side of the air floating video3due to unnecessary light can be erased.

In addition, when the above-described video light control sheet334is arranged on the front surface of the retroreflector5as illustrated inFIG.6B, reflection of external light on the retroreflector5can be reduced. Accordingly, the retroreflector5can be prevented from standing out as whitish due to reflection of external light inside the retroreflector5. Further, when the above-described video light control sheet334is arranged on the front surface of the retroreflector5, a background of the air floating image3is close to black. That is, the luminance of the background of the air floating image3decreases, thereby producing an effect of improving an apparent contrast of the air floating image3.

Furthermore, a place where the above-described video light control sheet334is arranged may be a back surface of the retroreflector5, i.e., a surface on the opposite side to the side on which the air floating image3is formed as illustrated inFIG.6C. As a result, ghost images to be respectively generated on both side of the air floating video3due to unnecessary light irradiated toward the retroreflector5from the video display apparatus1can be erased.

Further, when the video light control sheet334is arranged on the upper side (front surface) or the lower side (back surface) of the retroreflector5, as illustrated inFIGS.6B and6C, unlike when the video light control sheet334is arranged on the front surface of the video display apparatus1as illustrated inFIG.6A, moire due to a pitch of pixels on the liquid crystal display panel11and an interference of the video light control sheet334does not occur. That is, striped shades due to the pitch of pixels and the interference of the video light control sheet334does not occur.

Therefore, in cases illustrated inFIGS.6B and6C, there is also an effect of eliminating the necessity of performing a fine adjustment during assembly by making an array or columns or rows of pixels on the liquid crystal display panel11have an angle with respect to columns formed by arranging transparent silicone and black silicone in the video light control sheet334in order not to generate the above-described moire.

Furthermore, here, an arrangement of the above-described video light control sheet334is not limited to arrangement positions respectively illustrated inFIGS.6A,6B, and6C. As a specific example,FIG.6Dillustrates an example in which the video light control sheet334is arranged between the retroreflector5and a position where the air floating image3is formed.FIG.6Eillustrates an example in which the video light control sheet334is arranged between the retroreflector5and the video display apparatus1.

FIG.6Dillustrates the example in which the video light control sheet334is arranged between the retroreflector5and the position where the air floating image3is formed.

Specifically, the video light control sheet334is arranged in a space between the retroreflector5and the air floating image3, that is, spaces respectively exist between the video light control sheet334and the retroreflector5and between the video light control sheet334and the air floating video3. Further, inFIG.6D, the video light control sheet334is arranged perpendicularly to video light (indicated by a dotted line arrow) from the retroreflector5. This configuration makes it possible to erase ghost images to be respectively generated on both side of the air floating video3due to unnecessary light, and further to reduce reflection of external light on the retroreflector5. Furthermore, the retroreflector5stands out as whitish due to reflection of external: light inside the retroreflector5. Accordingly, the retroreflector5can be prevented from standing out as whitish by reducing the reflection of the externa light on the retroreflector5. Further, in the arrangement illustrated inFIG.6D, a background of the air floating video3is the video light control sheet334. As a result, a background color of the air floating video3is close to black. That is, the luminance of the background of the air floating video3decreases. Accordingly, there is an effect of improving an apparent contrast of the air floating image3.

The space exists between the video light control sheet334and the retroreflector5. Accordingly, even when respective pitches of pixels on the video light control sheet334and the retroreflector5are close values, e.g., both the pitches are values in the vicinity of 100 μm, moire due to an interference between the video light control sheet334and the retroreflector5does not occur in the formed air floating image3.

Then,FIG.6Eillustrates the example in which the video light control sheet334is arranged between the retroreflector5and the video display apparatus1. Specifically, the video light control sheet334is arranged in a space between the retroreflector5and the video display apparatus1, that is, spaces respectively exist between the retroreflector5and the video light control sheet334and between the video light control sheet334and the video display apparatus1. Further, inFIG.6E, the video light control sheet334is arranged perpendicularly to video light (indicated by a solid line arrow) from the video display apparatus1. This configuration makes it possible to erase ghost images to be respectively generated on both side of the air floating video3because unnecessary light emitted toward the retroreflector5from the video display apparatus1is reduced by the video light control sheet334. Further, the video light control sheet334exists in a background of the retroreflector5. Accordingly, a viewing person cannot recognize that the video light control sheet334exists.

Furthermore, in the case illustrated inFIG.6E, the space exists between the video light control sheet334and the retroreflector5or between the video light control sheet334and the video display apparatus1. Accordingly, even when respective pitches of pixels on the video light control sheet334, the retroreflector5, and the video display apparatus1are close values, e.g., all the three pitches are values in the vicinity of 100 μm, moire due to an interference does not occur in the formed air floating image3.

AlthoughFIGS.6D and6Erespectively illustrate the example in which the video light control sheet334is arranged in the space between the retroreflector5and the position where the air floating image3is formed and the example in which the video light control sheet334is arranged in the space between the retroreflector5and the video display apparatus1without being affixed to the retroreflector5, the video light control sheet334has a thickness of about 0.2 mm and is thin or light. Accordingly, in order to hold the video light control sheet334on the space, a member that holds the video light control sheet334such as a frame or a support made of resin may be appropriately provided.

<Second Configuration Example of Retroreflection Optical System Forming Air floating video Information Display System>

FIG.7is a diagram illustrating a configuration of a principal part of a retroreflective optical system in another example for implementing the air floating video information display system according to the embodiment of the present invention. The air video information display system is a system suitable for a viewing person to observe an air floating video obliquely from above. A video display apparatus1is configured to include a liquid crystal display panel11as a video display element and a light source apparatus13that generates light with a specific polarized wave having a narrow-angle diffusion property. The liquid crystal display panel11is composed of a liquid crystal display panel having a screen size ranging from a small screen size of about 5 inches to a large screen size exceeding 80 inches. Video light from the liquid crystal display panel11is emitted toward a retroreflector (retroreflection portion or a retroreflection plate)5.

Light from the light source apparatus13having a narrow divergence angle, described below, is incident on the liquid crystal panel11to generate a video luminous flux having a narrow divergence angle and make the video luminous flux incident on the retroreflector5, thereby obtaining an air floating image3. The air floating video3is formed at a position symmetric to the video display apparatus1with the retroreflector5used as a plane of symmetry. In order to erase a ghost image to be generated to obtain a high-quality air floating video3at this time, a video light control sheet334having a structure illustrated inFIG.12(A)is provided on the emission side of the liquid crystal panel11so that a diffusion property in an unnecessary direction may be controlled. Note that the video light control sheet334illustrated inFIG.7may be expressed as a diffusion property control sheet. Furthermore, as video light from the liquid crystal panel11, an S-polarized wave may be used because the reflectance thereof on a reflector such as the retroreflector can be made, in principle, high. However, when the viewing person uses polarized sunglasses, an aerial floating image is reflected or absorbed by the polarized sunglasses. Accordingly, as a countermeasure for this, there is provided a depolarization element339that optically converts a part of video light with a specific polarized wave into the other polarized wave and spuriously converts the video light into natural light, so that the viewing person can view a satisfactorily air floating video even if he or she uses the polarized sunglasses. These are optically bonded with an adhesive338, a light reflection surface does not occur, not deteriorating the image quality of the air floating image.

Examples of f commercially available products of the depolarization element include COSMO SHINE SRF (manufactured by TOYOBO CO., LTD.) and Depolarization Adhesive (manufactured by Nagase & Co., Ltd.). For the COSMO SHINE SRF (manufactured by TOYOBO CO., LTD.), an adhesive is bonded onto an image display apparatus to reduce reflection on an interface therebetween, thereby making it possible to improve an illuminance. Further, when the depolarization adhesive is used, a colorless and transparent plate and an image display apparatus are affixed to each other with the depolarization adhesive interposed therebetween. The video light control sheet334is also provided on a video emission surface of the retroreflector5, to erase ghost images to be respectively generated on both sides of a regular image of the air floating video3due to unnecessary light. In this example, the retroreflector5is arranged to be parallel to a horizontal plane on a space and is configured such that the air floating video3can be displayed to be inclined by θ1with respect to the horizontal plane. Accordingly, the video display apparatus1is configured such that its display surface is inclined by θ1toward the opposite side to the air floating video3with respect to the horizontal plane. Furthermore, in this example, the video display apparatus1includes the liquid crystal display panel11and the light source apparatus13that generates light with a specific polarized wave having a narrow-angle diffusion property.

<Third Configuration Example of Retroreflection Optical System Forming Air floating video Information Display System>

FIG.8is a diagram illustrating a configuration of a principal part of a retroreflective optical system in another example for implementing the air floating video information display system. The spatial video information display system is a system suitable for a viewing person to observe an air floating video from the front and obliquely from above. A video display apparatus1is configured to include a liquid crystal display panel11as a video display element and a light source apparatus13that generates light with a specific polarized wave having a narrow-angle diffusion property. The liquid crystal display panel11is composed of a liquid crystal display panel having a screen size ranging from a small screen size of about 5 inches to a large screen size exceeding 80 inches.

Video light from the liquid crystal display panel11is emitted toward a retroreflector5. Light from the light source apparatus13having a narrow divergence angle, described above, is incident on the liquid crystal panel11, to generate a video luminous flux having a narrow divergence angle and make the video luminous flux incident on the retroreflector5, thereby obtaining an air floating image3. The air floating video3is formed at a position symmetric to the video display apparatus1with the retroreflector5used as a plane of symmetry.

In order to erase a ghost image to be generated in the air floating image3to obtain a high-quality air floating video3, a video light control sheet334is provided on the emission side of the liquid crystal panel11illustrated inFIG.12Aso that a diffusion property in an unnecessary direction may be controlled. On the other hand, a video light control sheet334is also provided on a video emission surface of the retroreflector5, as illustrated inFIG.12(B), so that ghost images to be respectively generated on both sides of a regular image of the air floating video3due to unnecessary light may be erased. Here, the video light control sheet334may also be expressed as a diffusion property control sheet. The retroreflective sheet5is inclined (by θ2) with respect to a horizontal plane so that the air floating image3can be generated at an angle θ1 with respect to the horizontal plane. Accordingly, when the configuration illustrated inFIG.8is incorporated into an upper portion of a KIOSK terminal, for example, to display an air floating video as an avatar on an upper end portion of the terminal, video light is directed to the eyes of a viewing person, so that the high-luminance air floating video can be viewed.

In order to obtain the air floating video3at a desired elevation angle and position, an angle of inclination θ2 of the retroreflector5, an angle of inclination θ3 of the video display apparatus1, and their respective positions may be optimally designed, like in the first and second examples.

<Fourth Configuration Example of Retroreflection Optical System Forming Air floating video Information Display System>

FIG.9Ais a diagram illustrating a configuration of a principal part of a retroreflective optical system in another example for implementing the air floating video information display system. The air video information display system is a system suitable for a viewing person to observe an air floating video obliquely from above. A video display apparatus1is configured to include a liquid crystal display panel11as a video display element and a light source apparatus13that generates light with a specific polarized wave having a narrow-angle diffusion property. The liquid crystal display panel11is composed of a liquid crystal display panel having a screen size ranging from a small screen size of about 5 inches to a large screen size exceeding 80 inches.

In order to make video light from the liquid crystal display panel11obliquely incident on a retroreflector5arranged at an opposing position, as illustrated inFIG.9A, a linear fresnel sheet105as illustrated inFIG.10may be arranged close to a video light emission surface of the liquid crystal display panel11in the video display apparatus1to refract the video light in a desired direction. A convex and concave portion is formed on a front surface of the linear fresnel sheet105illustrated inFIG.10. In this example, zigzag-like-shaped or mountain-shaped grooves each having an inclined portion are formed. The front surface of the linear fresnel sheet105is a surface opposing the liquid crystal display panel11. The linear fresnel sheet105having such a shape transmits light, so that the light is refracted. When light is incident on the inclined portion of the mountain-shaped groove, the light is emitted at a predetermined angle of refraction. The linear fresnel sheet105has the convex and concave portion on a surface opposing the liquid crystal display panel11. InFIG.10, light from the liquid crystal display panel11is incident from the groove side of the linear fresnel sheet105, is refracted at an angle θ8, and is emitted at an angle θ9. Note that the linear fresnel sheet105illustrated inFIG.9Amay be expressed as a luminous flux traveling direction change member or a luminous flux traveling direction change sheet. At this time, a light shielding layer is provided on a vertical surface of the linear fresnel to block incidence of the video light from other than the fresnel lens, thereby making it possible to prevent unnecessary light from being generated. Furthermore, antireflection films are respectively provided on video light emission and incidence surfaces of the linear fresnel sheet to prevent unnecessary light from being generated, thereby making it possible to obtain a good property.

Light is emitted toward the retroreflector5by the above-described linear fresnel sheet105. Light from the light source apparatus13having a narrow divergence angle, described below, is incident on the liquid crystal panel11to generate a video luminous flux having a narrow divergence angle and make the video light flux incident on the retroreflector5, thereby obtaining an air floating image3. The air floating image3is formed at a position symmetric to a display surface of the video display apparatus1with a retroreflector2used as a plane of symmetry. In this example, the retroreflector2and the video display apparatus1are respectively arranged at opposing positions. Accordingly, when the viewing person looks into the retroreflector5in the air floating video information display apparatus, a video displayed on the liquid crystal panel11overlaps the air floating video, thereby significantly reducing the image quality of the air floating video.

In order to prevent the above-described video light from overlapping the air floating video, a video light control sheet334is provided on the video light emission surface of the liquid crystal panel11. A view/light path control film (VCF) manufactured by Shin-Etsu Polymer Co., Ltd., for example, is suitable as the video light control sheet334, and its structure is a sandwich structure obtained by alternately arranging transparent silicone and black silicone and arranging synthetic resin on a light incidence/emission surface, thereby making it possible to expect a similar effect to that of the external light control film in this example. At this time, in the view/light path control film (VCF), transparent silicone and black silicone each extending in a predetermined direction are alternately arranged. Accordingly, the view/light path control film (VCF) may be arranged to reduce moire to be generated by pixels on the liquid crystal panel11and a pitch of the external light control film by inclining respective extension directions of transparent silicone and black silicone in the video light control sheet334(by θ10 in the drawing) in an up-down direction of an array direction of the pixels, as illustrated inFIG.11.

In the fourth example, the retroreflector5is arranged parallel to a bottom surface of a housing. This results in a deterioration in the image quality of the air floating video3to be generated when external light is incident on the retroreflector5to enter the housing. In order to erase a ghost image to be generated in the air floating image3to obtain a high-quality air floating video3, the video light control sheet334is provided on the emission side of the liquid crystal panel11so that a diffusion property in an unnecessary direction may be controlled, as illustrated inFIGS.12A and12B, like in the second and third examples. On the other hand, the video light control sheet334is also provided on a video emission surface of the retroreflector5so that ghost images to be respectively generated on both sides of a regular image as the air floating video3due to unnecessary light may be erased. Here, the video light control sheet334may also be expressed as a diffusion property control sheet. A structure described above is arranged inside the housing to prevent external light from being incident on the retroreflector5, thereby preventing ghost images from being generated.

<Fifth Configuration Example of Retroreflection Optical System Forming Air floating video Information Display System>

Here, in the retroreflection optical systems used to respectively implement the air floating video information display systems illustrated inFIGS.6to8, an angle formed between the video display apparatus1and the second retroreflector5is an angle θ2 in the example illustrated inFIG.6A, for example. When the angle θ2 is 10 degrees, video light emitted from the video display apparatus1is incident on the second retroreflector5at an angle of incidence (an angle formed between a line perpendicular to the second retroreflector5and incident light) of 10 degrees, and the video light is reflected by a micromirror formed inside the retroreflector5to form the air floating video3at a position plane-symmetric to a display surface of the video display apparatus1with respect to the retroreflection member5, that is, a position at an angle of 10 degrees (=θ1) with respect to the retroreflector5.

At this time, as can be seen from an internal configuration of the retroreflector5illustrated inFIG.2, when video light emitted from the video display apparatus1is incident on the second retroreflector5at an angle of incidence of 45 degrees, the incident video light is most efficiently reflected, that is, the loss of a light amount is minimum, thereby obtaining a most desirable configuration.

However, when an angle formed between the video display apparatus1and the second retroreflector5, i.e., an angle θ2 is set to a smaller value in order to thin the air floating video display system, as described above, video light emitted from the video display apparatus1is incident on the second retroreflector5at an angle of incidence of 10 degrees when the angle θ2 is 10 degrees in the example illustrated inFIG.6A, for example, thereby making it possible to achieve thinning of the air floating video display system, while the utilization efficiency of the video light decreases, resulting in a significant decrease in the luminance of the air floating video3to be formed. Specifically, there occurs a problem that the luminance of the air floating video3to be formed decreases to one-fifth to one-fourth that when video light emitted from the video display apparatus1is incident on the second retroreflector5at an angle of incidence of 45 degrees.

An angle formed between the video display apparatus1and the second retroreflector5, i.e., an angle θ2=10 degrees, which is essential to thin the air floating video display system, needs to be maintained. Accordingly, a solution to implement a configuration in which video light emitted from the video display apparatus1is incident on the second retroreflector5at an angle of incidence as close to 45 degrees as possible has been studied. If this can be implemented, the luminance of the air floating video3finally formed can increase to four times to five times those in the examples illustrated inFIGS.6to8, thereby making it possible to obtain an air floating video3that is brighter and excellent in visibility with the air floating video display system itself having a thin shape.

FIG.9Bis a diagram illustrating a specific solution to the above-described problems.FIG.9Bis a diagram illustrating an example in which the linear fresnel sheet105is arranged, for example, on the display screen of the video display apparatus1. In order to make video light from the liquid crystal display panel11obliquely incident on the retroreflector5, the linear fresnel sheet105, as illustrated inFIG.10, is arranged close to a video display surface of the liquid crystal display panel11in the video display apparatus1so that the video light may be refracted in a desired direction. Note that the linear fresnel sheet105may be expressed as a luminous flux traveling direction change member or a luminous flux traveling direction change sheet.

When the linear fresnel sheet105is arranged on a front surface of the video display apparatus1, as illustrated inFIG.9B, an angle of video light to be emitted from the video display apparatus1, i.e., an angle of incidence on the second retroreflector5can be changed. The linear fresnel sheet105is arranged on an emission surface of the liquid crystal display panel11in the video display apparatus1or a front surface of the liquid crystal display panel11in the video display apparatus1. For example, inFIG.9B, in the video light emitted from the video display apparatus1, a direction of light rays to be incident on the retroreflector5from the video display apparatus1is bent by 30 degrees by the linear fresnel sheet105. That is, an angle formed between the video display apparatus1and the light rays to be incident on the retroreflector5is 30 degrees. As a result, an angle of incidence at which the video light is incident on the second retroreflector5is 40 degrees. Therefore, when the linear fresnel sheet105is arranged, the angle of incidence on the second retroreflector5is close to 45 degrees as an ideal angle. Accordingly, the luminance of the air floating video3formed by a configuration illustrated inFIG.9Bis improved by about three or four times that in the configuration illustrated inFIG.6A.

Here, as illustrated inFIG.9B, when the air floating video display system is arranged on a desk for the viewing person of the air floating video, the viewing person looks down the air floating video3at an angle θ6, like in the configuration illustrated inFIG.6A. At this time, an image forming position of the air floating video3is an optimal arrangement in which the air floating video is viewed by being arranged such that an angle θ2 formed between the display surface of the video display apparatus1and the retroreflector5and an angle θ1 formed between the retroreflector5and the air floating video3are substantially equal to each other, i.e., θ1=θ2. As described above, the fifth configuration of the retroreflection system makes it possible to solve the problem that the luminance of the air floating video3decreases while implementing thinning of the air floating video display system.

<First Configuration Example of Air floating video Information Display System>

A first example of the air floating video information system using the above-described four retroreflection optical systems is illustrated inFIG.13. A retroreflector5is fixed by adhesion or fixed by bonding to a transparent sheet100. A structure in which an image forming position of an air floating video3can be varied is used as a structure in which a distance between a video display apparatus1and the retroreflector5can be varied so that a movement can be provided to the air floating video, thereby making it possible to implement a video information display apparatus capable of spuriously displaying a three-dimensional air floating video.

<Second Configuration Example of Air floating video Information Display System>

A second example of the air floating video information display system will be described with reference toFIG.14.FIG.14illustrates an example in which an air floating video display apparatus202is incorporated into a tablet terminal. The air floating video display apparatus202and a planar display200are provided in the same housing201, and a sensing unit203that covers the planar display200and the whole of a display image204on the spatial floating video display202is provided at respective starting points of the planar display200and the air floating video204in the same plane as the air floating video204, and is provided in the same plane like a sensing area226. If the number of sensing areas described above is two or more, the sensing areas may respectively exist in parallel with or in front of or behind each other on planes, or may exist in the same plane. The air floating video display apparatus202and the planar display200may be together installed in the same housing201. Although description is made using the planar display200in the present embodiment, not only the planar display but also a display may be used. In the second configuration example, the sensing area increases in height toward the back side from a front surface of the apparatus, and has a slope. This implements an easy-to-input arrangement. The sensing unit will be described in detail below.

The video information display system is not easily affected by external light when the wavelength of light source light of a TOF system as a distance measurement system of the sensing unit203to be used is a long wavelength of 900 (nm) or more. At this time, a user falsely feels as if a spatial operation input to be performed for the displayed air floating video204can be similarly performed for a video display surface of the planar display200. Accordingly, the user can perform the spatial operation input without directly touching a display surface of the planar display200.

Furthermore, the inventors have found out by an experiment to what extent the planar display200and the sensing area226may be spaced apart from each other for an operator's finger not to touch a front surface of the planar display200even if an operator performs a spatial operation on the basis of a screen displayed on the planar display200. As a result, it has been found out by the experiment that a possibility that the operator directly touches the screen of the planar display200can be set to 50% or less by spacing an image forming position of the air floating video204by 40 mm or more apart from the planar display200. Furthermore, when the image forming position is spaced by 50 mm or more, the operator does not directly touch the planar display200.

Note that the configuration illustrated inFIG.14may be incorporated into not only the tablet terminal but also various types of display apparatuses such as an ATM, an automatic ticketing machine, a KIOSK terminal, and a stationary display apparatus.

<Third Configuration Example of Air floating video Information Display System>

A third example of the air floating video information display system will be described with reference toFIG.15.FIG.15illustrates an example in which an air floating video display apparatus202is incorporated into a tablet terminal. The air floating video display apparatus202and a planar display200are provided in the same housing201. There are a first sensing unit203athat senses a first sensing area (sensing region)226athat covers an image forming area of an air floating video204in the air floating video display apparatus202and a second sensing unit203bthat senses a second sensing area226bthat covers an image display area of the planar display200. The first sensing area226aand the second sensing area226bare respectively provided at starting points of the air floating video display apparatus202and the planar display200. Further, the first sensing area226aand the second sensing area226bare arranged close to each other. The first sensing area and the second sensing area exist in parallel with or in front of or behind each other, respectively, on planes. As illustrated inFIG.15, the first sensing area and the second sensing area may be configured to exist in the same plane. The air floating video display apparatus202and the planar display200may be together installed in the same housing201. Although description is made using the planar display200in the present embodiment, not only the planar display but also a display may be used. In this example, the air floating video display apparatus202is arranged substantially parallel to an image display surface of the planar display200. The sensing units used here will be described in detail below.

In the third example of the video information display system described above, a user falsely feels as if a spatial operation input to be performed for the displayed air floating video204can also be similarly performed for the video display surface of the planar display200. Accordingly, the user can perform the spatial operation input without directly touching a display screen of the planar display200.

At this time, as a result of evaluating a touch of a finger on a planar display200in a trial product using an actual machine, when an image forming position of an air floating video204is spaced by 50 mm or more apart from a planar display200, an operator could perform a spatial operation input to a video information display system without directly touching a screen of the planar display200.

Note that the configuration illustrated inFIG.15may be incorporated into not only the tablet terminal but also various types of display apparatuses such as an ATM, an automatic ticketing machine, a KIOSK terminal, and a stationary display apparatus.

<Technical Means for Sensing Air Video>

A sensing technique for spuriously operating an air floating video for a viewing person (operator) to be bidirectionally connected to an information system via an air floating video display apparatus will be described below.

In an air floating video information system, sensing information together with the air floating video is read by a two-dimensional sensor described below, thereby making it possible to perform an image operation for a display video.

The sensing technique for spuriously operating the air floating video in order for the viewing person (operator) to be bidirectionally connected to the information system via the air floating video display apparatus will be described below.FIG.16is a principle diagram for illustrating the sensing technique. There is provided a distance measurement apparatus203that contains a TOF (time of flight) system corresponding to the air floating video. A near-infrared LED (light emitting diode) as a light source is made to emit light in synchronization with a signal from the system. An optical element for controlling a divergence angle is provided on the light ray emission side of the LED, and high-sensitivity avalanche diodes each having a picosecond time resolution as a light receiving element are paired and aligned in a transverse direction to correspond to an area. The LED as the light source emits light in synchronization with the signal from the system, and a phase Δt shifts by a time period elapsed until the light is reflected by an object to be distance-measured (a tip of a finger of the viewing person) to return to a light receiving part. A distance of the object is calculated from the time difference Δt, to sense a position and a movement of the finger of the operator as two-dimensional information together with positional information of a plurality of sensors arranged in parallel. Further, it is possible to implement an air floating information display system or an air floating video display apparatus having a sensing function of hardly erroneously detecting a display screen of a planar display and an air floating video.

<Technical Means for Reducing Ghost Image>

Technical means for implementing a high-quality air video display apparatus in which a ghost image is reduced as an air floating video display apparatus will be described with reference toFIG.12. In order to control a divergence angle of video light from a liquid crystal panel13as a video display element in a desired direction, a video light control sheet334may be provided on an emission surface of the liquid crystal panel13. Furthermore, the video light control sheet334is provided on one or both of a light ray emission surface and a light ray incidence surface of a retroreflector to absorb extraordinary light that generates a ghost image.

FIG.12illustrates a specific method for applying a video light control sheet334to an air video display apparatus. The video light control sheet334is provided on an emission surface of a liquid crystal panel335as a video display element. At this time, the following two methods are effective to reduce moire to be generated by pixels on a liquid crystal panel13and an interference due to a pitch of transmission parts336and light absorption parts337in the video light control sheet334.

(1) The video light control sheet334is arranged to be inclined by θ10, as illustrated inFIG.11, with respect to vertical stripes occurring by the transmission part and the light absorption part in the video light control sheet334and an array of pixels on the liquid crystal panel335(denoted by a liquid crystal panel11inFIG.11).

(2) Letting A be a size of the pixels on the liquid crystal panel335and letting B be a pitch of the vertical stripes in the video light control sheet334, a ratio (B/A) of these is selected to exclude integral multiples.

One pixel339on the liquid crystal panel is formed by arranging pixels in three RGB colors in parallel, and is generally square. Accordingly, occurrence of the above-described moire cannot be suppressed on an entire screen. Accordingly, it has been experimentally found out that the inclination θ10 described in (1) may be optimized in a range from 5 degrees to 25 degrees such that an occurrence position of the moire can be arranged while being intentionally shifted to a place where an air floating video is not displayed. The liquid crystal panel has been described as an example to reduce the moire. However, for moire occurring between a retroreflector5and the video light control sheet334, a large moire having a large wavelength and having a frequency low enough to be recognizable even visually can be reduced by optimally inclining the video light control sheet while focusing on an X axis, as illustrated inFIG.4, because the retroreflector5and the video light control sheet334are linear structures.

FIG.12(A)is a vertical sectional view of the video display apparatus1according to the invention of the present application in which the video light control sheet334is arranged on a video light emission surface of the liquid crystal panel335. The video light control sheet334is configured by alternately arranging the light transmission parts336and the light absorption parts337, and is fixed by adhesion to a video light emission surface of the liquid crystal panel335by an adhesive layer338.

Further, when a WUXGA liquid crystal display panel of 7 inches (1920×1200 pixels) is used as the video display apparatus1, as described above, even if one pixel (one triplet) (A in the drawing) is about 80 μm, a sufficient transmission property and a diffusion property of video light from the video display apparatus causing generation of extraordinary light are controlled to reduce ghost images to be generated on both sides of the air floating image if a pitch B including a transmission portion d2of 300 μm and a light absorption portion d1of 40 μm in the video light control sheet334is 340 μm, for example. At this time, if the thickness of the video control sheet is set to two-thirds or more of the pitch B, a ghost reduction effect is significantly improved.

FIG.12(B)is a vertical sectional view of the retroreflector according to the invention of the present application in which the video light control sheet334is arranged on a video light emission surface of the retroreflector5. The video light control sheet334is configured by alternately arranging the light transmission parts336and the light absorption parts337, and is arranged to be inclined at an angle of inclination θ1 to match an emission direction of retroreflected light. As a result, extraordinary light to be generated as the above-described retroreflection occurs is absorbed, while regularly reflected light can be transmitted without any loss.

When the WUXGA liquid crystal display panel of 7 inches (1920×1200 pixels) is used, even if one pixel (one triplet) (A in the drawing) is about 80 μm, a sufficient transmission property and a diffusion property of video light from the video display apparatus causing generation of extraordinary light in the retroreflector are controlled to reduce ghost images to be generated on both sides of the air floating image if a pitch B including a transmission portion d2of 400 μm and a light absorption portion d1of 20 μm in the retroreflector is 420 μm, for example.

On the other hand, the above-described video light control sheet334prevents external light from the outside world from entering the air floating video display apparatus, thereby also leading to an improvement in reliability of components. A view/light path control film (VCF) manufactured by Shin-Etsu Polymer Co., Ltd., for example, is suitable as the video light control sheet, and its structure is a sandwich structure obtained by alternately arranging transparent silicone and black silicone and arranging synthetic resin on a light incidence/emission surface, thereby making it possible to expect a similar effect to that of the external light control film in this example.

<Performance of Liquid Crystal Panel>

Meanwhile, a general TFT (thin film transistor) liquid crystal panel differs in luminance and contrast performance depending on a mutual property of a liquid crystal and a light polarization plate based on a light emission direction. In an evaluation in a measurement environment illustrated inFIG.29, as a property of a luminance and a viewing angle in a panel short-side (up-down) direction, a property (+5 degrees in this example) at an angle slightly shifting from an emission angle perpendicular to a panel surface (an emission angle of 0 degrees) is excellent, as illustrated inFIG.31. This is because a light twisting property is not 0 degrees when an applied voltage is maximum in the short-side (up-down) direction of the liquid crystal panel.

On the other hand, a contrast performance in the panel short-side (up-down) direction is excellent in a range from −15 degrees to +15 degrees, as illustrated inFIG.33, and its most excellent property is obtained in use in a range of +10 degrees around 5 degrees when combined with a luminance property.

As a property of a luminance and a viewing angle in a panel long-side (left-right) direction, a property at an emission angle perpendicular to a panel surface (an emission angle of 0 degrees), as illustrated inFIG.30, is excellent. This is because a light twisting property is 0 degrees when an applied voltage is maximum in the long-side (left-right) direction of the liquid crystal panel.

Similarly, a contrast performance in the panel long-side (left-right) direction is excellent in a range from −5 degrees to −10 degrees, as illustrated inFIG.32, and its most excellent property is obtained in use in a range of +5 degrees around −5 degrees when combined with a luminance property. Accordingly, an emission angle of video light to be emitted from the liquid crystal panel improves an image quality and a performance of the video display apparatus1by making light incident on a liquid crystal panel in a direction in which a most excellent property is obtained by luminous flux direction conversion means (reflection surfaces307and314, etc.) provided in a light guiding body of the light source apparatus13, described above, and modulating the light in response to a video signal.

In order to maximize the luminance and the contrast property of the liquid crystal panel as a video display element, light incident on the liquid crystal panel from a light source is set to the above-described range so that a video quality of an air floating video can be improved.

<Method for Controlling Light Source Light>

In the present embodiment, in the video display apparatus1configured by including the light source apparatus13and the liquid crystal display panel11in order to improve the utilization efficiency of a luminous flux emitted from the light source apparatus13and significantly reduce power consumption, a video light ray, the luminance of which is modulated in response to a video signal, after being incident on the liquid crystal panel11at such an angle of incidence that a property of the liquid crystal panel11is maximum from the light source apparatus13and is emitted toward a retroreflector. At this time, it is desired to increase the degree of freedom of an arrangement of the liquid crystal panel11and the retroreflector in order to reduce a set volume of the air floating video information display system. Furthermore, the following technical means is used to form a floating video at a desired position and ensure an optimal directionality after retroreflection.

A transparent sheet composed of an optical component such as a linear fresnel lens illustrated inFIG.10as a light direction conversion panel is provided on a video display surface of the liquid crystal panel11, to control an emission direction of a luminous flux incident on a retroreflective optical member with a high directionality provided thereto and determine an image forming position of the air floating video. Accordingly, video light from the video display apparatus1efficiently reaches an observer, like laser light, with a high directionality (straightness). As a result, it is possible to display a high-quality floating video with a high resolution and to significantly reduce power consumption by the video display apparatus1including the light source apparatus13.

<Example 1 of Video Display Apparatus>

FIG.22illustrates another example of a specific configuration of a video display apparatus1. A light source apparatus13illustrated inFIG.22is similar to a light source apparatus illustrated inFIG.23or the like. The light source apparatus13is configured by housing an LED, a collimator, a composite diffusion block, a light guiding body, and the like in a case made of plastic, for example, and a liquid crystal display panel11is attached to its upper surface. Further, LED (light emitting diode) elements14aand14bas semiconductor light sources and an LED substrate on which a control circuit for the elements is mounted are attached to one side surface of the case of the light source apparatus13, and a heat sink as a member for cooling heat to be generated by the LED elements and the control circuit is attached to an outer side surface of an LED substrate (not illustrated).

Further, a liquid crystal display panel frame attached to an upper surface of the case is configured by having the liquid crystal display panel11attached to the frame, further FPC (flexible printed circuits) (not illustrated) electrically connected to the liquid crystal display panel11, and the like attached thereto. That is, the liquid crystal display panel11as a liquid crystal display element, together with the LED elements14aand14bas solid light sources, modulates the intensity of transmitted light, thereby generating a display video, on the basis of a control signal from a control circuit (not illustrated here) constituting an electronic apparatus.

<Example 1 of Light Source Apparatus in Example 1 of Video Display Apparatus>

Then, a configuration of an optical system such as the light source apparatus housed in the case will be described in detail with reference toFIGS.22(a)and22(b) together withFIG.21. InFIGS.21and22, the LEDs14aand14bconstituting the light source are illustrated, and are respectively attached to predetermined positions relative to collimators15. Note that each of the collimators15is formed of light transmittable resin such as acrylic resin. Then, the collimator15has an outer peripheral surface156having a conically convex shape obtained by rotating a paraboloidal cross section, and has a concave portion153having a convex portion (e.g., a convex lens surface)157in a central portion of its apex portion (the side contacting the LED substrate), as also illustrated inFIG.22(b).

Further, a planar portion (the opposite side to the above-described apex portion) of the collimator15has a convex lens surface protruding outward (or may be a concave lens surface recessed inward)154in its central portion. Note that the paraboloidal surface156forming the outer peripheral surface having a conical shape of the collimator15is set within a range of an angle at which light to be emitted in a circumferential direction from the LEDs14aand14bcan be totally reflected by its inside, or has a reflection surface formed thereon.

Further, each of the LEDs14aand14bis arranged at a predetermined position on a surface of a substrate102as its circuit board. The substrate102is arranged on and fixed to the collimator15such that the LED14aor14bon the surface is positioned in a central portion of the concave portion153.

According to such a configuration, among lights to be radiated from the LED14aor14bby the above-described collimator15, particularly the light to be radiated upward (in a rightward direction in the drawing) from the central portion of the collimator15is collected into collimated light by the two convex lens surfaces157and154forming an outer shape of the collimator15. Further, the light to be emitted in a circumferential direction from the other portion is reflected by the paraboloidal surface forming the outer peripheral surface having the conical shape of the collimator15, and is similarly collected into collimated light. In other words, the collimator15having a convex lens formed in its central portion and a paraboloidal surface formed in its peripheral portion makes it possible to extract almost all of the lights generated by the LED14aor14bas collimated light and to improve the utilization efficiency of the generated lights.

Note that a polarization conversion element21is provided on the light emission side of the collimator15. The polarization conversion element21may be referred to as a polarization conversion member. The polarization conversion element21is configured by combining a light transmittable member having a shape of a prism that is a parallelogram in cross section (hereinafter referred to as a parallelogram prism) and a light transmittable member having a shape of a prism that is a triangle in cross section (hereinafter referred to as a triangle prism) and arranging a plurality of light transmittable members in an array parallel to a surface perpendicular to an optical axis of the collimated light from the collimator15, as also apparent fromFIG.22(a). Furthermore, polarization beam splitters (hereinafter abbreviated as “PBS films”)211and reflection films212are alternately provided on an interface between the adjacent light transmittable members arranged in an array, and an emission surface, from which light that has been incident on the polarization conversion elements21and transmitted by the PBS film211is emitted, is provided with a λ/2phase plate213.

The emission surface of the polarization conversion element21is further provided with a composite diffusion block16having a rectangular shape, as also illustrated inFIG.22(a). That is, lights emitted from the LED14aor14bare incident on the composite diffusion block16as collimated light by the function of the collimator15, and are diffused by a texture161on the emission side, to reach a light guiding body17.

The light guiding body17is a member formed of light transmittable resin such as acrylic resin into a shape of a bar that is substantially triangular in cross section (seeFIG.23(b)), and includes a light guiding body light incidence part (surface)171opposing an emission surface of the composite diffusion block16with a first diffusion plate18ainterposed therebetween, a light guiding body light reflection portion (surface)172forming an inclined surface, a light guiding body light emission part (surface)173opposing the liquid crystal display panel11as a liquid crystal display element with a second diffusion plate18binterposed therebetween, as also apparent fromFIG.25.

On the light guiding body light reflection part (surface)172in the light guiding body17, a large number of reflection surfaces172aand connection surfaces172bare alternately formed in a serrated shape, as also illustrated inFIG.23as its partial enlarged view. Then, the reflection surface172a(a right upward line in the drawing) forms an (n: a natural number, e.g., 1 to 130 in this example) with respect to a horizontal surface indicated by a one-dot and dash line in the drawing. Here, an is set to 43 degrees or less (but 0 degrees or more) as an example.

The light guiding body incidence part (surface)171is formed into a curved convex shape inclined toward the light source side. Accordingly, collimated light from the emission surface of the composite diffusion block16is diffused through the first diffusion plate18aand is incident on the light guiding body incidence part (surface)171, to reach the light guiding body light reflection portion (surface)172while being slightly bent (deflected) upward by the light guiding body light incidence part (surface)171, and is reflected here, to reach the liquid crystal display panel11provided on the emission surface on the upper side of the drawing, as also apparent from the drawing.

The video display apparatus1described in detail above, including a modularized S-polarized wave light source apparatus, can be manufactured in a small size and at a low cost, simultaneously with more improving the light utilization efficiency and its uniform illumination property. Note that the polarization conversion element21is attached to the back of the collimator15in the above description, the present invention is not limited to that. Even if the polarization conversion element21is provided in an optical path leading to the liquid crystal display panel11, a similar function and effect can be obtained.

Note that the large number of reflection surfaces172aand connection surfaces172bare alternately formed in a serrated shape on the light guiding body light reflection portion (surface)172, an illumination luminous flux is totally reflected on each of the reflection surfaces172ato propagate upward, and is further incident on a light direction conversion panel54that adjusts a directionality as a substantially collimated diffusion luminous flux by a narrow-angle diffusion plate provided on the light guiding body light emission part (surface)173, and is incident on the liquid crystal display panel11in an oblique direction. Although the light direction conversion panel54is provided between the light guiding body emission surface173and the liquid crystal display panel11in this example, a similar effect is obtained even if provided on the emission surface of the liquid crystal display panel11.

Light emitted from the liquid crystal display panel11has similar diffusion properties, respectively, in a screen horizontal direction (a display direction corresponding to an X axis of a graph inFIG.28(A)) and a screen vertical direction (a display direction corresponding to a Y axis of a graph inFIG.28(B)), as illustrated in respective plot curves of a “conventional property (X-direction)” inFIG.28(A)and a “conventional property (Y-direction)” inFIG.28(B), for example, in a general apparatus for TV use.

On the other hand, a diffusion property of a luminous flux emitted from the liquid crystal display panel in this example is a diffusion property, as illustrated in respective plot curves of an “example 1 (X-direction)” inFIG.28(A)and an “example 1 (Y-direction)” inFIG.28(B), for example.

In a specific example, when a viewing angle having a luminance that is 50% (a luminance decreasing to about half) of a luminance in a front view (an angle of 0 degrees) is set to 13 degrees, the viewing angle is an angle that is about one-fifth that of a diffusion property (an angle of 62 degrees) of a general apparatus for household TV use. Similarly, in an example of a case where viewing angles in a vertical direction on the upper side and the lower side are set to be unequal, a reflection angle and an area of a reflection surface of a reflection-type light guiding body, for example, are optimized such that the viewing angle on the upper side is suppressed (narrowed) to about one-third the viewing angle on the lower side.

When the viewing angle and the like are set, as described above, the light amount of a video that propagates in a viewing direction of a user is more significantly increased (significantly improved in terms of brightness of the video) than that and the luminance of the video is 50 times or more that in a conventional liquid crystal TV.

Furthermore, in a case of a viewing angle property illustrated in an “example 2” inFIG.28, when a viewing angle having a luminance of 50% (a luminance decreasing to about half) of a luminance of a video obtained in a front view (an angle of 0 degrees) is set to 5 degrees, the viewing angle is an angle that is about one-twelfth (a narrow viewing angle) that of a diffusion property (an angle of 62 degrees) of a general apparatus for household TV use. Similarly, in an example of a case where viewing angles in a vertical direction on the upper side and the lower side are set to be equal, a reflection angle and an area of a reflection surface of a reflection-type light guiding body, for example, are optimized such that the viewing angles in the vertical direction are suppressed (narrowed) to about one-twelfth that in the conventional technique.

When such a setting is performed, the luminance (light amount) of a video that propagates in a viewing direction (a line-of-sight direction of a user) is more significantly improved than that and the luminance of the video is 100 times or more that in the conventional liquid crystal TV.

When the viewing angle is set to a narrow angle, as described above, an amount of a luminous flux that propagates in a viewing direction can be concentrated, resulting in a significantly improved light utilization efficiency. As a result, even if a general liquid crystal display panel for TV use is used, a significant improvement in luminance can be implemented with similar power consumption by adjusting a light diffusion property of the light source apparatus, thereby enabling a video display apparatus corresponding to an information display system for bright outdoors.

When a large liquid crystal display panel is used, light on the periphery of a screen is directed inward to propagate toward a viewing person when the viewing person faces the center of the screen, so that a full-screen performance in terms of screen brightness is improved. InFIG.25, a convergence angle between a long side of the liquid crystal display panel and a short side of the liquid crystal display panel when using a distance L from the liquid crystal display panel to the viewing person and a panel size (a screen ratio 16:10) of the video display apparatus as parameters is found.

A drawing on the upper side ofFIG.25presupposes a case where a video is viewed such that the screen of the liquid crystal display panel is portrait-oriented (hereinafter also referred to as “vertically-long use”). In this case, the convergence angle may be set to match the short side of the liquid crystal display panel (see a direction indicated by an arrow V inFIG.25as needed). As a more specific example, when a viewing distance is 0.8 m in vertically-long use of a 22″ panel, for example, as referred to by a plot graph inFIG.15, the convergence angle is set to 10 degrees so that video light from each of corners (four corners) of the screen can be effectively projected and outputted toward the viewing person.

Similarly, if the convergence angle is set to 7 degrees when a viewing distance is 0.8 m in the case of viewing in vertically-long use of a 15″ panel, video light from each of four corners of the screen can be effectively caused to propagate toward the viewing person. As described above, video light on the periphery of the screen is caused to propagate toward the viewing person at a position optimal to view the center of the screen depending on the size of the liquid crystal display panel and whether the use is vertically-long use or horizontally-long use, thereby making it possible to improve a full-screen performance in terms of screen brightness.

As a basic configuration, when a luminous flux having a narrow-angle directionality is made incident on the liquid crystal display panel11by the light source apparatus, as illustrated inFIG.26, described above, and others, and the luminance thereof is modulated to match a video signal, an air floating video obtained by reflecting video information displayed on the screen of the liquid crystal display panel11by a retroreflector is displayed outside or inside a room through a transparent sheet100.

A plurality of examples will be described below for other examples of the light source apparatus. The other examples of the light source apparatus may be all used in place of the light source apparatus in the above-described example of the video display apparatus.

When the large liquid crystal display panel is used, the light on the periphery of the screen is directed inward to propagate toward the viewing person when the viewing person faces the center of the screen, so that the full-screen performance in terms of screen brightness is improved, as described above. On the other hand, a binocular parallax occurs depending on which of the left and right eyes of the viewing person is used to perform visual recognition. InFIG.26, a convergence angle between a long side of the liquid crystal display panel and a short side of the liquid crystal display panel when using a distance L from the liquid crystal display panel to the viewing person and a panel size (a screen ratio 16:10) of the video display apparatus as parameters is found using respective positions of the left and right eyes as a reference.

The smaller a panel size is and the closer a viewing distance is, the larger a convergence angle in a binocular view with left and right eyes becomes. Particularly when a small panel of 7 inches or less is used, a convergence angle due to a binocular parallax is an important requirement, and thus is designed such that video light is directed toward an optimal viewing range of the system by enlarging the light diffusion property of the light source illustrated inFIG.28or making the light source have a directionality when the panel size is 7 inches or less, for example.

Furthermore, to obtain horizontal and vertical directionalities and a diffusion property depending on a required specification of the system, a shape, a surface roughness, a slope, and the like of the reflection surface of the light guiding body in the above-described light source apparatus13need to be optimally designed.

<Example 1 of Light Source Apparatus>

Then, another example of a light source apparatus will be described with reference toFIG.17.FIGS.17(a)and17(b) are diagrams with a liquid crystal display panel11and a diffusion plate206partially omitted to describe a light guiding body311.

FIG.17illustrates a state where a substrate102is provided with LEDs14constituting a light source. Each of the LEDs14and the substrate102are respectively attached to predetermined positions relative to a reflector15.

As illustrated inFIG.17(a), the LEDs14are aligned in a direction parallel to a side (a short side in this example) of the liquid crystal display panel11on the side on which a reflector300is arranged. In the illustrated example, the reflector300is arranged to correspond to an arrangement of the LEDs. Note that a plurality of reflectors300may be arranged.

In one specific example, each of the reflectors300is formed of a plastic material. Although the reflector300may be formed of a metal material or a glass material as another example, the plastic material is more easily molded. Accordingly, the reflector made of the plastic material is used in this example. As illustrated inFIG.17(b), a surface on the inner side (the right side in the drawing) of the reflector300includes a reflection surface (which may be hereinafter referred to as a “paraboloidal surface”)305having a shape obtained by cutting a paraboloidal surface on a meridian. The reflector300reflects divergent light to be emitted from the LED14by the above-described reflection surface305(the paraboloidal surface), to convert the divergent light into substantially collimated light and make the converted light incident on an end surface of the light guiding body311. As a specific example, the light guiding body311is a transmission-type light guiding body.

The reflection surface of the reflector300has a shape asymmetric with respect to an optical axis of light emitted from the LED14. Further, the reflection surface305of the reflector300is the paraboloidal surface, as described above. The LED is arranged on a focal point of the paraboloidal surface, to convert a luminous flux after reflection into substantially collimated light.

The LED14cannot convert the divergent light from the LED into completely collimated light even if arranged on the focal point of the paraboloidal surface because it is a surface light source, but does not influence the performance of the light source in the invention of the present application. The LED14and the reflector300are paired. In order to ensure a predetermined performance in an attachment accuracy±40 μm of the LED14to the substrate102, the number of LEDs to be attached to the substrate should be a maximum of ten, and may be suppressed to about five in consideration of mass productivity.

Although the LED14and the reflector300are made partially close to each other, heat can be radiated into a space on the side of an opening of the reflector300. Therefore, an increase in temperature of the LED can be reduced. Accordingly, the reflector300as a plastic molded product can be used. As a result, the shape accuracy of the reflection surface can be improved by ten times or more that of a reflector made of a glass material, thereby making it possible to improve a light utilization efficiency.

On the other hand, a reflection surface is provided on a bottom surface303of the light guiding body311, and light from the LED14is converted into a collimated luminous flux by the reflector300, is then reflected by the reflection surface, and is emitted toward the liquid crystal display panel11arranged to oppose the light guiding body311. The reflection surface provided on the bottom surface303may have a plurality of surfaces respectively having different slopes in a traveling direction of the collimated luminous flux from the reflector300, as illustrated inFIG.17. Each of the plurality of surfaces respectively having different slopes may have a shape extending in a direction perpendicular to the traveling direction of the collimated luminous flux from the reflector300.

Further, a shape of the reflection surface provided on the bottom surface303may be a planar shape. At this time, light reflected by the reflection surface provided on the bottom surface303of the light guiding body311is refracted by a refraction surface314provided on a surface, which opposes the liquid crystal display panel11, of the light guiding body311, thereby adjusting a light amount and an emission direction of the luminous flux propagating toward the liquid crystal display panel11with a high accuracy.

The refraction surface314may have a plurality of surfaces respectively having different slopes in the traveling direction of the collimated luminous flux from the reflector300, as illustrated inFIG.17. Each of the plurality of surfaces respectively having different slopes may have a shape extending in the direction perpendicular to the traveling direction of the collimated luminous flux from the reflector300. Light reflected by the reflection surface provided on the bottom surface303of the light guiding body311is refracted toward the liquid crystal display panel11by the respective slops of the plurality of surfaces. Further, the refraction surface314may be a transmission surface.

Note that when the diffusion plate206is located in front of the liquid crystal display panel11, the light reflected by the reflection surface is refracted toward the diffusion plate206by the plurality of slops of the refraction surface314. That is, an extension direction of the plurality of surfaces respectively having different slopes of the refraction surface314and an extension direction of the plurality of surfaces respectively having different slopes of the reflection surface provided on the bottom surface303are parallel to each other. When both the extension directions are made parallel to each other, an angle of light can be more preferably adjusted. On the other hand, the LED14is soldered to the metallic substrate102. Accordingly, heat generated by the LED can be radiated into air through the substrate.

Further, although the reflector300may contact the substrate102, a space may be provided therebetween. When the space is provided, the reflector300is arranged to adhere to a housing. When the space is provided, heat generated by the LED can be radiated into air, resulting in an increased cooling effect. As a result, an operation temperature of the LED can be reduced, thereby implementing a maintenance of a luminous efficiency and an increase in lifetime.

<Another Example 2 of Light Source Apparatus>

Then, a configuration of an optical system related to a light source apparatus having a light utilization efficiency that is improved by 1.8 times that of the light source apparatus illustrated inFIG.17using light polarization conversion will be described in detail with reference toFIGS.18A,18B,18C, and18D. Note that illustration of a sub reflector308is omitted inFIG.18A.

FIGS.18A,18B, and18Ceach illustrate a state where a substrate102is provided with LEDs14constituting a light source. The reflector300and each of the LEDs14are set as a pair of blocks, to constitute a unit312including a plurality of blocks.

Among them, a base material320illustrated inFIG.18A(2) is a base material of the substrate102. Generally, the metallic substrate102has heat. Accordingly, in order to (thermally) insulate heat of the substrate102, a plastic material or the like may be used for the base material320. A material for and a shape of a reflection surface of the reflector300may be the same material and shape as those in the example of the light source apparatus illustrated inFIG.26.

Further, the reflection surface of the reflector300may have a shape asymmetric with respect to an optical axis of light emitted from the LED14. The reason for this will be described with reference toFIG.18A(2). In this example, the reflection surface of the reflector300is a paraboloidal surface, like in the example illustrated inFIG.17, and the center of a light emission surface of the LED as a surface light source is arranged at a focal position of the paraboloidal surface.

Further, in terms of a property of the paraboloidal surface, lights respectively emitted from four corners of the light emission surface are also converted into a substantially collimated luminous flux, and only differ in emission directions. Accordingly, even if a light emission part has an area, an amount and a conversion efficiency of light to be incident on a polarization conversion element21arranged in a succeeding stage are hardly affected if a distance between the polarization conversion element and the reflector300is small.

Further, even if an attachment position of each of the LEDs14shifts within an XY plane with respect to a focal point of the corresponding reflector300, an optical system capable of reducing a reduction in the light conversion efficiency due to the above-described reason can be implemented. Furthermore, even if the attachment position of the LED14varies in a Z-axis direction, the collimated luminous flux obtained by the conversion only moves within a ZX plane, so that an attachment accuracy of the LED as the surface light source can be significantly reduced. Although the reflector300having a reflection surface obtained by cutting a part of the paraboloidal surface on a meridian has also been described in this example, the LED may be arranged in a cut portion as a reflection surface of the entire paraboloidal surface.

On the other hand, this example has a characteristic configuration in which divergent light from the LED14is reflected by a paraboloidal surface321and converted into substantially collimated light, is then incident on an end surface of the polarization conversion element21in the succeeding stage, and is equalized to have a specific polarized wave by the polarization conversion element21, as illustrated inFIGS.18B(1) and18C. According to this characteristic configuration, in the present invention, the light utilization efficiency is 1.8 times that in the example illustrated inFIG.26, thereby making it possible to implement a highly efficient light source.

Note that all substantially collimated lights obtained by reflecting the divergent light from the LED14having the paraboloidal surface321are not all equal at this time. Therefore, an angular distribution of the reflected light is adjusted by a reflection surface307having a plurality of slops so that the reflected light can be incident on the liquid crystal display panel11in a vertical direction toward the liquid crystal display panel11.

Here, in the example illustrated in the drawing, an arrangement is made such that a direction of light (a principal ray) entering the reflector from the LED and a direction of light entering the liquid crystal display panel are substantially parallel to each other. This arrangement is easily made in terms of design, and an arrangement of a heat source below the light source apparatus is more preferable because air is released upward so that an increase in temperature of the LED can be reduced.

Further, as illustrated inFIG.18B(1), in order to improve a capture rate of the divergent light from the LED14, a luminous flux that cannot be captured by the reflector300is reflected by a sub reflector308provided on a light shielding plate309arranged above the reflector, is reflected by an inclined surface of the sub reflector310below the reflector, and is incident on an effective region of the polarization conversion element21in the succeeding stage, thereby further improving the light utilization efficiency. That is, in this example, a part of the light reflected by the reflector300is reflected by the sub reflector308, and the light reflected by the sub reflector308is reflected in a direction toward a light guiding body306by the sub reflector310.

The substantially collimated luminous flux equalized to have a specific polarized wave by the polarization conversion element21is reflected toward the liquid crystal display panel11arranged to oppose the light guiding body306by a reflection shape provided on a front surface of the reflection-type light guiding body306. At this time, a light amount distribution of the luminous flux to be incident on the liquid crystal display panel11is optimally designed depending on a shape and an arrangement of the reflector300, described above, and a shape (cross-sectional shape), a slope, and a surface roughness of a reflection surface of the reflection-type light guiding body.

A plurality of reflection surfaces are arranged to oppose the emission surface of the polarization conversion element as the reflection surface shape provided on the front surface of the light guiding body306, and a slope, an area, a height, and a pitch of the reflection surfaces are optimized depending on a distance from the polarization conversion element21, thereby setting the light amount distribution of the luminous flux to be incident on the liquid crystal display panel11to a desired value, as described above.

When the reflection surface307provided on the reflection-type light guiding body is configured to have a plurality of slops on its one surface, as illustrated inFIG.18B(2), reflected light can be adjusted with a higher accuracy. Note that as a configuration in which the reflection surface has a plurality of slops on its one surface, a region to be used as the reflection surface may be a plurality of surfaces, a polygonal surface, or a curved surface. Furthermore, a more uniform light amount distribution is implemented by a diffusion function of a diffusion plate206. A uniform light amount distribution of light to be incident on the diffusion plate on the side closer to the LED can be implemented by changing the slopes of the reflection surface.

In this example, a plastic material such as heat-resistant polycarbonate is used as a base material for the reflection surface307. Further, an angle of the reflection surface307immediately after emission from a λ/2plate213changes depending on a distance between the λ/2plate and the reflection surface.

In this example, the LED14and the reflector300are also partially close to each other. However, heat can be radiated into a space on the side of the opening of the reflector300, so that an increase in temperature of the LED can be reduced. Further, the substrate102and the reflector300may be arranged upside down relative to those illustrated inFIGS.18A,18B, and18C.

However, if the substrate102is arranged on the upper side, the substrate102is close to the liquid crystal display panel11. Accordingly, a layout may be difficult. Therefore, an arrangement of the substrate102below the reflector300(the side farther from the liquid crystal display panel11), as illustrated in the drawing, makes a configuration inside the apparatus simpler.

A light incidence surface of the polarization conversion element21may be provided with a light shielding plate410such that unnecessary light is not incident on an optical system in the succeeding stage. Such a configuration makes it possible to implement a light source apparatus in which an increase in temperature is suppressed. Although a light polarization plate provided on a light incidence surface of the liquid crystal display panel11absorbs a luminous flux having equalized light polarization in the invention of the present application to reduce the increase in temperature, a part of light is absorbed by the incidence-side light polarization plate because its light polarization direction is rotated when reflected by the reflection-type light guiding body. Furthermore, the temperature of the liquid crystal display panel11also increases by an increase in temperature due to absorption in liquid crystals themselves and light incident on an electrode pattern. However, there is a sufficient space between the reflection surface of the reflection-type light guiding body306and the liquid crystal display panel11, thereby enabling natural cooling.

FIG.18Dillustrates a modification example of the light source apparatus illustrated inFIGS.18B(1) and18C.FIG.18D(1) illustrates a modification example of the light source apparatus illustrated inFIG.18B(1) with its part extracted. Other components are the same as those in the above-described light source apparatus illustrated inFIG.18B(1), and hence illustration and repetitive description thereof will be omitted.

First, in the example illustrated inFIG.18D(1), the height of a concave portion319in a sub reflector310is adjusted to be lower than that of a position of a fluorescent body114such that a principal ray of a fluorescence (see a straight line extending in a direction parallel to an X axis inFIG.18D(1)) to be outputted in a transverse direction (X-axis direction) from the fluorescent body114is released out of the concave portion319in the sub reflector310. Furthermore, the height of a light shielding plate410is adjusted to be lower in a Z-axis direction than that of a position of the fluorescent body114such that the principal ray of the fluorescence to be outputted in the transverse direction from the fluorescent body114is incident on an effective region of a polarization conversion element21without being blocked by the light shielding plate410.

Further, a reflection surface of a convex portion in convex and concave on an apex portion of the sub reflector310reflects light reflected by the sub reflector308to guide the light reflected by the sub reflector308into a light guiding body306. Accordingly, the height of the convex portion318in the sub reflector310is adjusted such that the light reflected by the sub reflector308is reflected and is incident on the effective region of the polarization conversion element21in a succeeding stage, thereby making it possible to further improve a light utilization efficiency.

Note that the sub reflector310is arranged to extend in one direction, as illustrated inFIG.18A(2), and has a convex and concave shape. Furthermore, on the apex portion of the sub reflector310, convex and concave including one or more convex portions are periodically arranged in one direction. Such a convex and concave shape enables a configuration in which the principal ray of the fluorescence to be outputted in the transverse direction from the fluorescent body114is incident on the effective region of the polarization conversion element21.

Further, the convex and concave shape of the sub reflector310is periodically arranged at a pitch at which the concave portion319is located at a position of an LED14. That is, each florescent body114is periodically arranged in one direction to correspond to an arrangement pitch of the concave portions in the convex and concave of the sub reflector310. Note that when the LED14includes the fluorescent body114, the florescent body114may be expressed as a light emission portion of a light source.

Further,FIG.18D(2) illustrates a modification example of the light source apparatus illustrated inFIG.18Cwith its part extracted. Other components are the same as those in the light source apparatus illustrated inFIG.18C, and hence illustration and repetitive description thereof will be omitted. As illustrated inFIG.18D(2), the sub reflector310may be eliminated. However, the height of the light shielding plate410is adjusted to be lower in the Z-axis direction than that of a position of the florescent body114such that the principal ray of the fluorescence to be outputted in the transverse direction from the fluorescent body114is incident on the effective region of the polarization conversion element21without being blocked by the light shielding plate410, like inFIG.18D(1).

Note that for the light source apparatus illustrated inFIGS.18A,18B,18C, and18D, a sidewall400may be provided to prevent dust from entering a space between the reflection surface of the reflection-type light guiding body306and the liquid crystal display panel11, prevent generation of stray light toward the outside of the light source apparatus, and prevent entrance of stray light from entering from the outside of the light source apparatus, as illustrated inFIG.18A(1). The sidewall400is arranged to sandwich a space between the light guiding body306and the diffusion plate206when provided.

The light emission surface of the polarization conversion element21that emits light polarization-converted by the polarization conversion element21faces a space surrounded by the sidewall400, the light guiding body306, the diffusion plate206, and the polarization conversion element21. Further, a reflection surface having a reflection film or the like is used as a surface, among inner surfaces of the sidewall400, of a portion that covers a space into which light is outputted from the emission surface of the polarization conversion element21(a space on the right side of the emission surface of the polarization conversion element21illustrated inFIG.18B(1)) from its side surface. That is, a surface of the sidewall400facing the above-described space includes a reflection region having a reflection film. When the surface, among the inner surfaces of the sidewall400, of the portion is used as a reflection surface, light reflected by the reflection surface can be reduced as light source light, thereby making it possible to improve the luminance of the light source apparatus.

The surface, among the inner surfaces of the sidewall400, of the portion that covers the polarization conversion element21from its side surface is set as a surface having a low light reflectance (a black surface having no reflection film, etc.). This is because light in an unexpected light polarization state occurs when reflected light occurs on the side surface of the polarization conversion element21, causing stray light. In other words, when the above-described surface is set as the surface having a low light reflectance, generation of stray light of a video and light in an unexpected polarization state can be prevented or suppressed. Alternatively, the sidewall400may be configured to have a hole through which air passes in its part to improve a cooling effect.

Note that each of the light source apparatus illustrated inFIGS.18A,18B,18C, and18Dhas been described on the premise of a configuration using the polarization conversion element21. However, the light source apparatus may be configured by eliminating the polarization conversion element21therefrom. In this case, a light source apparatus can be provided at a lower cost.

<Another Example 3 of Light Source Apparatus>

Then, a configuration of an optical system related to a light source apparatus using a reflection-type light guiding body304will be described in detail on the basis of the light source apparatus illustrated in the example 1 of the light source apparatus with reference toFIGS.19A(1),19A (2),19A (3), and19B.

FIG.19Aillustrate a state where a substrate102is provided with LEDs14constituting a light source. A collimator18and each of the LEDs14are set as a pair of blocks, to configure a unit328including a plurality of blocks. Since the collimator18in this example is close to the LED14, a glass material is used in consideration of a heat resistance. A shape of the collimator18is similar to the shape described in the collimator15illustrated inFIG.18. Further, a light shielding plate317is provided in a preceding stage where light is incident on a polarization conversion element21, to prevent or suppress incidence of unnecessary light on an optical system in a succeeding stage, thereby reducing an increase in temperature due to the unnecessary light.

Another configuration and effect of the light source illustrated inFIG.19Aare similar to those illustrated inFIGS.18A,18B,18C, and18D, and hence repetitive description thereof will be omitted. The light source apparatus illustrated inFIG.19Amay be provided with a sidewall, like those described inFIGS.18A,18B, and18C. A configuration and an effect of the sidewall have already described, and hence repetitive description thereof will be omitted.

FIG.19Bis a cross-sectional view ofFIG.19A(2). A configuration of a light source illustrated inFIG.19Bis common to a part of the structure of the light source illustrated inFIG.18, and has already been described inFIG.18, and hence repetitive description thereof will be omitted.

<Another Example 4 of Light Source Apparatus>

Then, in a light source apparatus illustrated inFIG.23, the collimator18and the LED14used in the light source apparatus illustrated inFIG.19are set as a pair of blocks, to configure the unit328including a plurality of blocks. A configuration of an optical system related to a light source apparatus using an LED and a reflection-type light guiding body504respectively arranged at both ends of a back surface of a liquid crystal display panel11will be described in detail with reference toFIGS.23(a),23(b), and23(c).

FIG.23illustrate a state where a substrate505is provided with LEDs14constituting a light source. A collimator18and each of the LEDs14are set as a pair of blocks, to configure a unit503including a plurality of blocks. Units503are respectively arranged at both the ends of the back surface of the liquid crystal display panel11(three units are arranged side by side in a short-side direction in this example). Light outputted from each of the units503is reflected by the reflection-type light guiding body504, and is incident on the liquid crystal display panel11(illustrated inFIG.23(c)) arranged to oppose the reflection-type light guiding body504.

The reflection-type light guiding body504is separated into two blocks respectively corresponding to units arranged at its ends and is arranged such that its central portion is the highest, as illustrated inFIG.23(c). Since the collimator18is close to the LED14, a glass material is used in consideration of a heat resistance against heat to be generated from the LED14. A shape of the collimator18is the shape described in the collimator15illustrated inFIG.18.

Light from the LED14is incident on a polarization conversion element501through the collimator18. A distribution of light to be incident on the reflection-type light guiding body504in a succeeding stage is adjusted depending on a shape of an optical element81. That is, a light amount distribution of a luminous flux to be incident on the liquid crystal display panel11is optimally designed by adjusting the above-described shape and an arrangement of the collimator18, the shape and a diffusion property of the optical element81, and a shape (cross-sectional shape) of a reflection surface of the reflection-type light guiding body, a slope of the reflection surface, a surface roughness of the reflection surface.

As the shape of the reflection surface provided on a front surface of the reflection-type light guiding body504, a plurality of reflection surfaces are arranged to oppose an emission surface of the polarization conversion element, as illustrated inFIG.23(b). A slope, an area, a height, and a pitch of the reflection surfaces are optimized depending on a distance from the polarization conversion element21. Further, a region to be the same reflection surface (i.e., a surface opposing the polarization conversion element) is separated into polyhedrons, so that a light amount distribution of a luminous flux to be incident on the liquid crystal display panel11can be set to a desired value (optimized), as described above.

One surface (a light reflection region) of the reflection surface provided on the reflection-type light guiding body is configured to have a shape having a plurality of slops (constituted by 14-separated surfaces respectively having different slops within an XY plane in an example illustrated inFIG.23), like in the reflection-type light guiding body described inFIG.18B, so that reflected light can be adjusted with a higher accuracy. Further, when a light shielding wall507is provided in order to prevent the reflected light from the reflection-type light guiding body from leaking through a side surface of the light source apparatus13, leak light can be prevented from being generated in a direction other than a desired direction (a direction toward the liquid crystal display panel11).

Further, the units503respectively arranged on the left and right of the reflection-type light guiding body504illustrated inFIG.23may be each replaced with the light source apparatus illustrated inFIG.18. That is, a plurality of light source apparatuses (each including a substrate102, a reflector300, an LED14, and the like) illustrated inFIG.18may be prepared, and the plurality of light source apparatuses may be respectively arranged at positions opposing one another, as referred to byFIGS.23(a),23(b), and23(c).

FIG.24(B)illustrates a light source apparatus configured by arranging six units503and six units503illustrated inFIG.24(A), respectively, on the upper and lower sides. As illustrated in the drawing, a current is controlled by a single power supply as a unit configuration in which five LEDs are arranged side by side to obtain a desired luminance. Accordingly, as a light source apparatus that illuminates a liquid crystal panel, each of the units can control a light source luminance for each region to be irradiated. In a configuration illustrated inFIG.24, there are a reflection surface502different from a reflection surface222and the reflection surface222. The reflection surface222has a shape like horizontal grids or a strip shape having a predetermined width. The reflection surface502has a shape like vertical and horizontal grids. A luminance and an angle of reflected light can be finely controlled by these shapes. Accordingly, even if a single light source is used for the planar display and the air floating video information apparatus illustrated in each ofFIGS.14and15, a light source luminance can be controlled for each irradiation region.

FIG.20is a cross-sectional view illustrating an example of a shape of the diffusion plate206. As described above, divergent light outputted from the LED is converted into substantially collimated light by the reflector300or the collimator18, is converted to have a specific polarized wave by the polarization conversion element21, and is then reflected by the light guiding body. Then, a luminous flux reflected by the light guiding body is incident on the liquid crystal display panel11after passing through a planar portion of an incidence surface of the diffusion plate206(see two solid-line arrows indicating “reflected light from the light guiding body” inFIG.19″).

A divergent luminous flux in light emitted from the polarization conversion element21is totally reflected by an inclined surface of a protrusion having a slope provided on the incidence surface of the diffusion plate206, and is incident on the liquid crystal display panel11. In order to totally reflect the light emitted from the polarization conversion element21by the inclined surface of the protrusion of the diffusion plate206, an angle of the inclined surface of the protrusion is changed on the basis of a distance from the polarization conversion element21. Letting a be an angle of the inclined surface of the protrusion on the side far from the polarization conversion element21or the side far from the LED and letting a′ be an angle of the inclined surface of the protrusion on the side close to the polarization conversion element21or the side close to the LED, α is smaller than α′ (α<α′). Such setting makes it possible to effectively use the luminous flux polarization-converted.

<Diffusion Property Control Technique for Video Display Apparatus>

Examples of a method for adjusting a diffusion distribution of video light from the liquid crystal display panel11include a method for providing a lenticular lens between the light source apparatus13and the liquid crystal display panel11or on the front surface of the liquid crystal display panel11to optimize a shape of the lens. That is, when the shape of the lenticular lens is optimized, an emission property of video light (hereinafter also referred to as a “video luminous flux”) to be emitted in one direction from the liquid crystal display panel11can be adjusted.

Alternatively or additionally, a microlens array may be arranged in a matrix shape on the front surface of the liquid crystal display panel11(or between the light source apparatus13and the liquid crystal display panel11) to adjust a mode of the arrangement. That is, when the arrangement of the microlens array is adjusted, an emission property in an X-axis direction and a Y-axis direction of the video luminous flux to be emitted from the video display apparatus1can be adjusted. As a result, a video display apparatus having a desired diffusion property can be obtained.

As a further configuration example, a combination of two lenticular lenses may be arranged or a sheet in which a microlens array is arranged in a matrix shape to adjust a diffusion property may be provided at a position through which video light to be emitted from the video display apparatus1passes. Such an optical system configuration makes it possible to adjust a luminance (relative luminance) of video light in an X-axis direction and a Y-axis direction depending on a reflection angle of the video light (a reflection angle when using reflection in a vertical direction as a reference (0 degrees)).

In this example, such a lenticular lens is used, so that an excellent optical property can be acquired, as illustrated in a graph (plot curves) of an “example 1 (Y-direction)” and an “example 2 (Y-direction)” inFIG.27(b), which clearly differs from a graph (plot curves) of a conventional property. Specifically, in the respective plot curves of the example 1 (Y-direction) and the example 2 (Y-direction), a luminance property in a vertical direction is made sharp, and a balance of a directionality in an up-down direction (a positive-negative direction of a Y axis) is further changed, thereby making it possible to increase a luminance (relative luminance) of light due to reflection and diffusion.

Accordingly, this example makes it possible to provide video light having a narrow diffusion angle (high straightness) and having only a specific polarized wave component, like video light from a surface light emission laser video source, and adjust the video light to suppress a ghost image, which has been generated in a retroreflector when the video display apparatus according to the related art is used, and make an air floating image generated by retroreflection efficiently reach the eyes of a viewing person.

Further, the above-described light source apparatus makes it possible to make a diffusion property (denoted by a “related-art property” in the drawings) of light emitted from a general liquid crystal display panel illustrated inFIGS.28(A) and28(B)have a directionality having a significantly narrow angle in both an X-axis direction and a Y-axis direction. In this example, a video display apparatus that emits a substantially collimated video luminous flux in a specific direction and emits light with a specific polarized wave can be implemented by providing such a directionality having a narrow angle.

FIG.27illustrates an example of a property of a lenticular lens to be used in this example. In this example, a property in an X-direction (vertical direction) with a Z axis as a reference is particularly illustrated, and a property O indicates a luminance property having a peak in a light emission direction at an angle close to 30 degrees upward from a vertical direction (0 degrees) and being symmetric in an up-down direction. Further, plot curves of a property A and a property B illustrated in a graph ofFIG.27further respectively indicate property examples in which a luminance (relative luminance) is increased by collecting upper video light having a peak luminance at an angle close to 30 degrees. Accordingly, in the properties A and B, the luminance (relative luminance) of light rapidly decreases in a region at an angle where a slope (an angle θ) in the X-direction from the Z axis exceeds 30 degrees (θ>30°), as can be seen from comparison with a plot curve of the property O.

That is, according to an optical system including the above-described lenticular lens, when a video luminous flux from the video display apparatus1is incident on a retroreflector, an emission angle and a viewing angle of video light having an equalized narrow angle by the light source apparatus13can be adjusted, and a degree of freedom of installation ofa retroreflective sheet can be significantly improved. As a result, a degree of freedom related to an image forming position of an air floating image that is formed at a desired position after being reflected or transmitted by a window glass can be significantly improved. As a result, the video light can be made to efficiently reach the eyes of a viewing person outside or inside a room as light having a narrow diffusion angle (high straightness) and having only a specific polarized wave component. This makes it possible for the viewing person to accurately recognize video light from the video display apparatus1to obtain information even if the intensity (luminance) of the video light is reduced. In other words, an output of the video display apparatus1is reduced, thereby making it possible to implement an information display system with low power consumption.

Various embodiments and examples (specific examples) to which the present invention is applied have been described in detail above. On the other hand, the present invention is not limited to only the above-described embodiment (specific examples), but includes various modification examples. For example, the above-described embodiment has described the entire system in detail to make the present invention easy to understand, and is not necessarily limited to one including all the described components. Further, some of components in an embodiment can be replaced with components in another embodiment, or components in another embodiment can be added to components in an embodiment. Further, for some of components in each embodiment, another component can be added, eliminated, or replaced.

The light source apparatus described above is not limited to the air floating video display apparatus, but is also applicable to an information display apparatus such as an HUD, a tablet, or a digital signage.

In the technique according to the present embodiment, the air floating video is displayed with high-resolution and high-luminance video information floating in air, thereby making it possible for a user to perform an operation without having concern about contact infection in infectious illness, for example. Use of the technique according to the present embodiment for a system to be used by a large number of unspecified users makes it possible to provide a non-contact user interface that the user can use without having concern by reducing a risk of contact infection in infectious illness. The present invention for providing such a technique contributes to “Goal3: Good Health and Well-being” in sustainable development goals (SDGs) advocated by the United Nations.

Further, in the above-described technique according to the embodiment, only regularly reflected d light is efficiently reflected with respect to a retroreflector by making a divergence angle of video light to be emitted small and equalizing the video light to have a specific polarized wave, resulting in a high light utilization efficiency, thereby making it possible to obtain a bright and clear air floating video. The technique according to the present embodiment makes it possible to provide a non-contact user interface capable of significantly reducing power consumption and being excellent in availability. The present invention for providing such a technique contributes to “Goal9: Industry, Innovation and Infrastructure” and “Goal11: Sustainable Cities and Communities” in sustainable development goals (SDGs) advocated by the United Nations.

Furthermore, the above-described technique according to the present embodiment makes it possible to form an air floating video based on video light having a high directionality (straightness). In the technique according to the present embodiment makes it possible to provide a non-contact user interface having less risk of a person other than a user looking into an air floating video by displaying video light having a high directionality even when displaying a video that requires a high security at an ATM of a bank, a ticketing machine of a station, or the like and a video having a high secret level that is desired to be kept secret from a person who faces the user. The present invention provides the above-described technique, thereby contributing to “Goal11: Sustainable Cities and Communities” in sustainable development goals (SDGs) advocated by the United Nations.

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