JP2017201418A - Screen and projection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To expand a view angle.SOLUTION: A screen is used by a projection device that projects projection light whose polarization property is linear polarization in a first direction. The screen includes: a polarization dependent optical element that has refractive power to linear polarization light in the first direction, but does not have refractive power to linear polarization light in a second direction intersecting with the first direction; a 1/4 wavelength plate that converts the polarization property of the projection light after passing through the polarization dependent optical element; and a retroreflective member that reflects the projection light after passing through the 1/4 wavelength plate. A refractive index in the second direction of the polarization dependent optical element does not change along the first direction.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a screen and a projection system using the screen.

  A screen having a Fresnel lens and a transparent resin layer provided with a light diffusing agent is known (Patent Document 1).

JP-A-5-11345

  The conventional screen has a problem that the viewing angle is narrow.

  A screen according to a first aspect of the present invention is a screen used in a projection device that projects projection light whose polarization characteristic is linearly polarized light in a first direction, and is refracted with respect to linearly polarized light in the first direction. A polarization-dependent optical element that has a force and has no refractive power with respect to linearly polarized light in the second direction intersecting the first direction, and a polarization characteristic of the projection light that has passed through the polarization-dependent optical element. A quarter-wave plate to be converted, and a retroreflecting member that reflects the projection light that has passed through the quarter-wave plate, and the refractive index in the second direction of the polarization-dependent optical element is It does not change along the first direction.

  According to the present invention, the viewing angle of the observer can be enlarged.

It is a block diagram which shows the structure of the projection system by the 1st Embodiment of this invention. It is the schematic which shows the structure of the screen by the 1st Embodiment of this invention. It is a figure which shows the refractive index distribution of a polarization dependence optical system. It is the figure which showed typically the refractive index change of a polarization dependence optical system. It is the figure which showed one structural example of the retroreflection member. It is an optical path diagram of a screen according to the first embodiment of the present invention. It is the schematic which shows the structure of the projection apparatus for projecting a three-dimensional image. It is an optical path figure of the screen by the 2nd Embodiment of this invention. It is an optical path diagram of a screen according to a third embodiment of the present invention.

-First embodiment-
FIG. 1 is a block diagram showing a configuration of a projection system according to a first aspect of the first embodiment of the present invention. A projection system 100 illustrated in FIG. 1 includes a projection device 1, a screen 2, and a display control device 3.

  The projection device 1 is an electronic device such as a projector or a digital camera with a projector. The projection device 1 projects a linearly polarized light beam related to a two-dimensional image or a three-dimensional image toward the screen 2 under the control of the display control device 3. The screen 2 reflects the projection light beam of the projection device 1 so that a two-dimensional image or a three-dimensional image can be observed within the viewing angle of the screen 2. In the following description, the projection apparatus 1 projects a p-polarized linearly polarized light beam.

  The display control device 3 includes a storage unit 10 and a control unit 11. The storage unit 10 is configured by a ROM, a hard disk, and the like, and stores image data and a control program executed by the control unit 11. The control unit 11 includes a CPU, a RAM, and the like, and functions as the display control unit 11a by executing a control program stored in the storage unit 10. The display control unit 11 a controls the projection device 1 based on the image data stored in the storage unit 10.

  The image data stored in the storage unit 10 is image data of a two-dimensional image or a three-dimensional image. The image data of the three-dimensional image is, for example, data converted into two-dimensional data by a known plenoptic camera or a light field camera.

  FIG. 2 is a schematic diagram showing the configuration of the screen 2 according to the second aspect of the first embodiment of the present invention. In FIG. 2, an x-axis direction, a y-axis direction, and a z-axis direction are set. The screen 2 has a structure in which the polarization-dependent optical element 61, the quarter wavelength plate 62, and the retroreflective member 64 are arranged in this order in the z-axis direction.

The polarization dependent optical element 61 is an optical member manufactured using a medium having refractive index anisotropy. For example, the polarization-dependent optical element 61 is manufactured using nematic liquid crystal or the like that is cured with ultraviolet rays by controlling the inclination of the refractive index ellipsoid using a zone plate disk as a mask material. Techniques for manufacturing an optical member such as the polarization-dependent optical element 61 are described in, for example, the following non-patent documents.
Gao-Sin Chen and Hui-Chen Yeh, "Polarization-selective color-filter Fresnel lens in polymer-stabilized cholesteric liquid crystals", JOURNAL OF APPLIED PHYSICS 112, 054501 (2012)

  Hereinafter, as an explanation of the first embodiment, the polarization-dependent optical element 61 has a Fresnel lens function having a positive refractive power with respect to the p-polarized component of the incident light beam, and is refracted with respect to the s-polarized component. It shall not have power.

  The quarter-wave plate 62 is disposed between the polarization-dependent optical element 61 and the retroreflective member 64 so as to be inclined by 45 degrees or 135 degrees with respect to the polarization plane of the incident light beam. The quarter-wave plate 62 changes the linearly polarized light beam into a circularly polarized light beam and the circularly polarized light beam into a linearly polarized light beam. The retroreflective member 64 is an optical member that reflects an incident light beam in a direction parallel to and opposite to the incident light beam.

  FIG. 3 is a diagram schematically showing the refractive index distribution of the medium of the polarization-dependent optical element 61. In FIG. 3, annular black belts 611 representing high refractive power portions and annular white belts 612 representing low refractive power portions are shown alternately and concentrically.

  FIG. 4 is a conceptual diagram illustrating a change in the refractive index of the polarization-dependent optical element 61 on the line segment S1 in FIG. 3 using a uniaxial refractive index ellipsoid. FIG. 4 shows a plurality of uniaxial refractive index ellipsoids 71a to 71c. In the refractive index ellipsoids 71a to 71c, the major axis direction of each ellipse is the optical axis direction, and the refractive index in the optical axis direction is n1. The refractive index in the biaxial direction perpendicular to the optical axis direction of the refractive index ellipsoids 71a to 71c is n2.

  The refractive index ellipsoid 71b shows a state in which the refractive index ellipsoid 71a is rotated 45 degrees counterclockwise about the axis perpendicular to the paper surface. The refractive index ellipsoid 71c shows a state in which the refractive index ellipsoid 71a is rotated 90 degrees counterclockwise about the axis perpendicular to the paper surface.

  In FIG. 4, the uniaxial refractive index ellipsoids 71a to 71c are arranged along the y-axis direction along the refractive index ellipsoid 71a, the refractive index ellipsoid 71b, the refractive index ellipsoid 71c, the refractive index ellipsoid 71a, and the refractive index ellipse. The body 71b, the refractive index ellipsoid 71c, and so on are arranged in this order. That is, the refractive index in the z-axis direction of the polarization-dependent optical element 61 changes in a sawtooth shape between n2 and n1 along the y-axis. Due to this change in refractive index, the polarization-dependent optical element 61 has a positive refractive power with respect to a p-polarized linearly polarized light beam. On the other hand, the refractive index in the x-axis direction of the polarization-dependent optical element 61 does not change along the y-axis direction and is n2. Therefore, the polarization-dependent optical element 61 does not have refractive power with respect to the s-polarized linearly polarized light beam.

  FIG. 5 is a view showing a configuration example of the retroreflective member 64. The retroreflective member 64 shown in FIG. 5 has a plurality of beads 51 densely arranged on a plane. The plurality of beads 51 have a refractive index of 2.0 and are made of a transparent optical material. The bead 51 has a hemispherical reflective layer 52 formed on a half of its surface, and the remaining half of the surface is exposed. The reflective layer 52 is formed by, for example, aluminum vapor deposition. The plurality of beads 51 are arranged such that the exposed side of the surface thereof faces the quarter wavelength plate 62. The retroreflective member 64 interposes an air layer 63 with a small thickness between the quarter-wave plate 62.

  In FIG. 5, the light beam L1 incident on the bead 51 from the direction of the arrow A1 is refracted at the boundary between the bead 51 and the air layer 63, enters the inside of the bead 51, and is reflected by the reflection layer 52 of the bead 51. Then, the light beam L1 is refracted again at the boundary between the bead 51 and the air layer 63 and is emitted to the air layer 63 in the direction of arrow A2, which is parallel to and opposite to the direction of arrow A1.

  FIG. 6 is an optical path diagram of the screen 2. In FIG. 6, in order to indicate that the polarization-dependent optical element 61 has a Fresnel lens function, the polarization-dependent optical element 61 is illustrated in a Fresnel shape. A p-polarized light beam L2 projected from the projection apparatus 1 (not shown in FIG. 6) onto the screen 2 is incident on the polarization-dependent optical element 61, refracted, and then incident on the quarter-wave plate 62. The light beam L2 becomes circularly polarized light at the quarter-wave plate 62 and enters the retroreflecting member 64. The light beam L2 is retroreflected in a direction parallel to and opposite to the direction of incidence on the retroreflective member 64, enters the quarter-wave plate 62 again, becomes s-polarized light, and enters the polarization-dependent optical element 61. . Since the polarization-dependent optical element 61 does not have a refractive index with respect to the s-polarized light beam L2, the s-polarized light beam L2 travels straight through the polarization-dependent optical element 61 and is emitted as an output light beam L3. The polarization-dependent optical element 61 expands the viewing angle by an angle θ with respect to the light beam incident on the polarization-dependent optical element 61 from all directions.

  FIG. 7 is a schematic diagram showing a configuration of the projection apparatus 1 for projecting a projection light beam of a three-dimensional image onto the screen 2. The projection apparatus 1 shown in FIG. 7 includes a three-dimensional image reproduction unit 20, an illumination optical system 21, and a projection optical system 22.

  The illumination optical system 21 is an optical system for illuminating the three-dimensional image reproduction unit 20, and includes, for example, a light source 40, a condenser lens 41, a polarizing plate 42, and an illumination polarization separation mirror 43. The light source 40 emits light beams of a plurality of colors in a time division manner. The condenser lens 41 converts the incident light beam into parallel light. The polarizing plate 42 extracts an s-polarized linearly polarized light beam from parallel light. The illumination polarization separation mirror 43 has a characteristic of reflecting the s-polarized light component of the incident light beam and transmitting the p-polarized light component, and reflects the s-polarized light beam from the polarizing plate 42 to the three-dimensional image reproducing unit 20.

  The three-dimensional image reproducing unit 20 includes a microlens array 30 and a two-dimensional display element 31. In the microlens array 30, a plurality of microlenses 231 are two-dimensionally arranged. In the two-dimensional display element 31, a plurality of display pixels 32 respectively corresponding to the plurality of microlenses 231 are two-dimensionally arranged. The two-dimensional display element 31 is composed of a display member such as a reflective LCOS (Liquid Crystal on Silicon).

  Image data relating to a three-dimensional image converted into two-dimensional data by a plenoptic camera or the like is input to the two-dimensional display element 31 by the display control unit 11a. Each of the display pixels 32 reflects the illumination light beam under the control of the display control unit 11a based on the image data regarding the three-dimensional image. When the display pixel 32 reflects the illumination light beam, the polarization plane of the illumination light beam is rotated by 90 degrees to be p-polarized light. The reflected p-polarized light beam from the display pixel 32 forms (reproduces) a three-dimensional image by the microlens 231, passes through the illumination polarization separation mirror 43, and is projected from the projection optical system 22 onto the screen 2. .

-Second embodiment-
A second embodiment of the present invention will be described. In the second embodiment of the present invention, the polarization characteristics of the polarization-dependent optical element in the screen are different from those in the first embodiment. The screen according to the second embodiment constitutes a projection system together with the projection device 1 and the display control device 3 as in the first embodiment. In the description of the second embodiment, it is assumed that the projection apparatus 1 projects a p-polarized linearly polarized light beam toward the screen.

  FIG. 8 is an optical path diagram of the screen 4 according to the second embodiment of the present invention. The screen 4 illustrated in FIG. 8 includes a polarization-dependent optical element 81 instead of the polarization-dependent optical element 61.

  Similar to the polarization-dependent optical element 61, the polarization-dependent optical element 81 is an optical member manufactured using a medium having refractive index anisotropy. The polarization-dependent optical element 81 is manufactured using, for example, a nematic liquid crystal that is cured with ultraviolet rays by controlling the inclination of the refractive index ellipsoid using a zone plate disk as a mask material. The polarization-dependent optical element 81 has a Fresnel lens function having a negative refractive power with respect to the s-polarized component of the incident light beam, and does not have a refractive power with respect to the p-polarized component.

  In FIG. 8, in order to show that the polarization-dependent optical element 81 has a Fresnel lens function, the polarization-dependent optical element 81 is illustrated in a Fresnel shape. A p-polarized light beam L4 projected on the screen 4 from the projection apparatus 1 (not shown in FIG. 8) travels straight through the polarization-dependent optical element 81 and enters the quarter-wave plate 62. The light beam L4 becomes circularly polarized light by the quarter wavelength plate 62 and enters the retroreflecting member 64. The light beam L4 is retroreflected in a direction parallel to and opposite to the direction of incidence on the retroreflecting member 64, enters the quarter-wave plate 62 again, becomes s-polarized light, and enters the polarization-dependent optical element 81. . The light beam L4 that has become s-polarized light is refracted by the polarization-dependent optical element 81 and is emitted as an outgoing light beam L5. In this way, the polarization-dependent optical element 81 expands the viewing angle by the angle θ with respect to the light beam incident on the polarization-dependent optical element 81 from all directions.

-Third embodiment-
A third embodiment of the present invention will be described. The third embodiment of the present invention is different from the first embodiment in that a circularly polarizing plate is further provided between the quarter-wave plate and the retroreflective member. FIG. 9 is an optical path diagram of a screen according to the third embodiment. The screen 6 shown in FIG. 9 includes a polarization-dependent optical element 61, a quarter-wave plate 62, a circularly polarizing plate 93, and a retroreflecting member 64. The polarization-dependent optical element 61, the quarter-wave plate 62, and the retroreflective member 64 are the same as those constituting the screen 2 of the first embodiment, and thus description thereof is omitted. In FIG. 9 also, the polarization-dependent optical element 61 is illustrated in a Fresnel shape in order to indicate that the polarization-dependent optical element 61 has a Fresnel lens function.

  The circularly polarizing plate 93 is an optical member manufactured using, for example, cholesteric liquid crystal, and allows right circularly polarized light and left circularly polarized light to pass therethrough but does not allow linearly polarized light beams to pass therethrough. The circularly polarizing plate 93 is disposed between the quarter-wave plate 62 and the retroreflective member 64, and converts a circularly polarized light beam from a light beam reciprocating between the quarter-wave plate 62 and the retroreflective member 64. Extract.

  A p-polarized light beam L6 projected from the projection device 1 (not shown in FIG. 9) onto the screen 6 is incident on the polarization-dependent optical element 61, refracted, and then incident on the quarter-wave plate 62. The light beam L6 is circularly polarized by the quarter-wave plate 62. For example, the light beam L6 is a right circularly polarized light beam. The right circularly polarized light beam L <b> 6 passes through the circularly polarizing plate 93 and enters the retroreflecting member 64. The light beam L6 is retroreflected in a direction parallel to and opposite to the direction of incidence on the retroreflective member 64 to become a left circularly polarized light beam. The left circularly polarized light beam L6 passes through the circularly polarizing plate 93 again, enters the quarter-wave plate 62, becomes s-polarized light, and enters the polarization-dependent optical element 61. Since the polarization-dependent optical element 61 does not have a refractive index with respect to the s-polarized light beam L6, the s-polarized light beam L6 travels straight through the polarization-dependent optical element 61 and is emitted as an output light beam L7. The polarization-dependent optical element 61 expands the viewing angle by an angle θ with respect to the light beam incident on the polarization-dependent optical element 61 from all directions. The quarter-wave plate 62 may change the p-polarized light beam L6 incident from the polarization-dependent optical element 61 into a left-circularly polarized light beam L6. In that case, the light beam L6 reflected by the retroreflecting member 64 becomes right circularly polarized light.

  Due to various disturbances, the light flux L6 reflected by the retroreflecting member 64 may cause polarization disturbance in a part thereof. For example, a part of the circularly polarized light beam L6 reflected by the retroreflecting member 64 may become linearly polarized light due to the influence of various disturbances. The light flux component due to the polarization disturbance deteriorates the image quality of the two-dimensional image or the three-dimensional image. By providing the circularly polarizing plate 93 between the quarter-wave plate 62 and the retroreflective member 64, it is possible to prevent a part of the light flux generated due to the polarization disturbance from entering the quarter-wave plate 62, It is possible to prevent deterioration of the image quality of the two-dimensional image and the three-dimensional image.

According to the embodiment described above, the following operational effects can be obtained.
A screen 2 according to the first embodiment is a screen used in the projection apparatus 1 that projects a p-polarized linearly polarized light beam, and includes a polarization-dependent optical element 61, a quarter-wave plate 62, and a retroreflective member. 64. The polarization-dependent optical element 61 has a positive refractive power with respect to the p-polarized component of the light beam and has no refractive power with respect to the s-polarized component. The quarter-wave plate 62 converts the polarization characteristics of the projection light that has passed through it. The retroreflection member 64 reflects the projection light that has passed through the quarter-wave plate 62. Conventionally, the viewing angle is expanded by diffusing the light beam, whereas the screen 2 uses the polarization-dependent optical element 61 to expand the viewing angle, so that a bright projected image can be observed. .

  The screen 4 according to the second embodiment is a screen used in the projection apparatus 1 that projects a p-polarized linearly polarized light beam, and includes a polarization-dependent optical element 81, a quarter-wave plate 62, and a retroreflective member. 64. The polarization-dependent optical element 81 has a negative refractive power with respect to the s-polarized component of the light beam and has no refractive power with respect to the p-polarized component. Also for the screen 4, since the viewing angle is enlarged using the polarization-dependent optical element 61, a bright projected image can be observed.

  In the screen 6 according to the third embodiment, a circularly polarizing plate 93 is interposed between the quarter-wave plate 62 and the retroreflective member 64. Since the circularly polarizing plate 93 does not allow light beams other than circularly polarized light to enter the quarter-wave plate 62 from the retroreflective member 64, polarization disturbance occurred in the retroreflective member 64 due to the influence of disturbance or the like. Even in this case, the image quality of the two-dimensional image or the three-dimensional image reproduced by the screen 6 does not deteriorate.

The embodiment described above can be implemented with the following modifications.
[Modification 1] The projection apparatus 1 projects a p-polarized linearly polarized light beam, but may project an s-polarized linearly polarized light beam. In this case, the polarization-dependent optical element 61 according to the first embodiment has a positive refractive power with respect to the s-polarized component of the light beam and does not have a refractive power with respect to the p-polarized component. . Further, the polarization-dependent optical element 81 according to the second embodiment has only to have a negative refractive power with respect to the p-polarized component of the light beam and not have a refractive power with respect to the s-polarized component.

[Modification 2] The projection apparatus 1 is not limited to the configuration shown in FIG. Specifically, the two-dimensional display element 31 may use a display member other than the reflective LCOS. For example, a reflective member other than LCOS such as DMD (Digital Mirror Device) may be used, transmissive liquid crystal such as transmissive LCOS may be used, an organic EL panel, a plasma display device, and the like. Thus, a self-luminous display device may be used. Further, when a reflective display member such as LCOS is used, the projection apparatus 1 may include a half mirror instead of the illumination polarization separation mirror 43. When a self-luminous display member is used instead of the two-dimensional display element 31, the illumination optical system 21 is not necessary. When a transmissive display member is used instead of the two-dimensional display element 31, it is preferable to arrange the illumination optical system 21 excluding the illumination polarization separation mirror 43 so that the illumination light beam is transmitted through the display member. Moreover, you may decide to further provide the memory | storage part 10 and the control part 11 of the display control apparatus 3. FIG.

[Modification 3] FIG. 5 shows a configuration example in which beads 51 are densely arranged on a plane as the retroreflective member 64. However, the retroreflecting member 64 may have any configuration as long as it has the property of reflecting the incident light beam in a direction parallel to and opposite to the incident light beam. For example, the retroreflective member 64 may be configured by combining a plurality of reflecting prisms.

  The embodiments and modifications described above are merely examples, and the present invention is not limited to these contents as long as the features of the invention are not impaired. Further, the embodiments and modifications described above may be combined and executed as long as the features of the invention are not impaired.

DESCRIPTION OF SYMBOLS 1 Projection apparatus 2,4 Screen 3 Display control apparatus 61,81 Polarization dependence optical element 62 1/4 wavelength plate 64 Retroreflective member 93 Circularly-polarizing plate 100 Projection system

Claims (7)

A screen used in a projection apparatus that projects projection light whose polarization characteristics are linearly polarized light in a first direction,
A polarization-dependent optical element having a refractive power with respect to the linearly polarized light in the first direction and having no refractive power with respect to the linearly polarized light in the second direction intersecting the first direction;
A quarter-wave plate for converting the polarization characteristics of the projection light that has passed through the polarization-dependent optical element;
A retroreflecting member that reflects the projection light that has passed through the quarter-wave plate;
With
The screen in which the refractive index in the second direction of the polarization-dependent optical element does not change along the first direction. The screen of claim 1.
The screen in which the first direction and the second direction are orthogonal. The screen according to claim 1 or 2,
A screen in which a refractive index in a traveling direction of the projection light of the polarization-dependent optical element changes along the first direction. The screen according to any one of claims 1 to 3,
The quarter-wave plate is a screen that converts the projected light that is reflected by the retroreflective member and reciprocates itself from the linearly polarized light in the first direction to the linearly polarized light in the second direction. The screen according to any one of claims 1 to 4,
The polarization-dependent optical element is a screen having a positive refractive power with respect to linearly polarized light in the first direction. The screen according to any one of claims 1 to 5,
The projection light interposed between the quarter-wave plate and the retroreflective member and made incident on the retroreflective member from the quarter-wave plate, and the quarter-wavelength from the retroreflective member A screen further comprising a circularly polarizing plate that extracts a circularly polarized light beam from the projection light incident on the plate. A screen according to any one of claims 1 to 6;
The projection device;
A projection system comprising:

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