Display device and optical system

Abstract

A display device of the present disclosure is provided with: a first projection optical system having a first display unit for displaying images; a second projection optical system having a second display unit for displaying images; and an illumination optical system for guiding light to the first projection optical system and the second projection optical system. The illumination optical system has: a light source that collimates and emits a light-source beam containing first polarized light and second polarized light; and a polarizing-beam splitter containing a splitting plane for splitting the light-source beam into a first beam in a first polarized-beam state and a second beam in a second polarized-beam state. The illumination optical system guides the first beam to the first display unit and guides the second beam to the second display unit. The first projection optical system projects an image displayed on the first display unit by using the first beam. The second projection optical system projects an image displayed on the second display unit by using the second beam.

Description

Display device and optical system

[0001] The present disclosure relates to a display device and an optical system.

[0002] For example, Patent Document 1 discloses a light source used in an image display device that includes a light modulation means that reflects irradiated light and performs light modulation according to an image signal, and a projection means that projects the reflected light from the light modulation means.

[0003] The light source described in Patent Document 1 includes a light emitting means and a polarization conversion means. The light emitting means emits light to be irradiated onto the light modulation means. The polarization conversion means is provided immediately after the light emitting means and converts the polarization direction of the light so that at least 50% of the light emitted from the light emitting means is polarized in a predetermined direction and emitted.

[0004] Japanese Patent Application Laid-Open No. 2000-221499

[0005] However, in Patent Document 1, there is still room for improvement in terms of miniaturization while improving the efficiency of light utilization from the light source.

[0006] The present disclosure provides a display device and an optical system that are miniaturized while improving the efficiency of light utilization from a light source.

[0007] The display device of the present disclosure comprises a first projection optical system having a first display unit that displays an image, a second projection optical system having a second display unit that displays an image, and an illumination optical system that guides light to the first projection optical system and the second projection optical system, wherein the illumination optical system has a light source that collimates and emits light source light including a first polarization and a second polarization, and a polarizing beam splitter that includes a splitting surface that splits the light source light into a first light having a first polarization state and a second light having a second polarization state, and the illumination optical system guides the first light to the first display unit and the second light to the second display unit, the first projection optical system projects an image displayed on the first display unit using the first light, and the second projection optical system projects an image displayed on the second display unit using the second light.

[0008] The optical system of the present disclosure is an optical system that guides light to a first display unit of a first projection optical system and a second display unit of a second projection optical system, and includes a light source that collimates and emits light source light including a first polarization and a second polarization, and a polarizing beam splitter that includes a splitting surface that splits the light source light into a first light having a first polarization state and a second light having a second polarization state, and guides the first light to the first display unit and the second light to the second display unit.

[0009] According to the present disclosure, it is possible to provide a display device and an optical system that are miniaturized while improving the efficiency of light utilization from a light source.

[0010] Schematic diagram for explaining the optical system in embodiment 1 Schematic diagram for explaining a head-mounted display including the optical system of embodiment 1 Schematic diagram for explaining a head-mounted display including the optical system of embodiment 1 Schematic diagram for explaining the optical system in embodiment 2 Schematic diagram for explaining the optical system in embodiment 3 Schematic diagram for explaining the optical system in embodiment 4 Schematic diagram for explaining the optical system in embodiment 5 Schematic diagram for explaining another example of the positional relationship between the retardation plate and the reflecting element Schematic diagram for explaining another example of the positional relationship between the retardation plate and the reflecting element Schematic diagram for explaining another example of the positional relationship between the retardation plate and the reflecting element Schematic diagram for explaining another example of the reflecting element Schematic diagram for explaining another example of the reflecting element Schematic diagram for explaining another example of the reflecting element Another example of the reflecting element Schematic diagram for explaining another example of the optical system Schematic diagram for explaining another example of the optical system Schematic diagram for explaining a display device in embodiment 6 Schematic diagram for explaining an example of the display device in embodiment 7 Schematic diagram for explaining another example of the display device in embodiment 7 Schematic diagram for explaining another example of the display device in embodiment 7 Schematic diagram for explaining an example of the display device in embodiment 8 Schematic diagram for explaining another example of the display device in embodiment 8 Schematic diagram for explaining another example of the display device in embodiment 8 Schematic diagram for explaining a display device in embodiment 9 Schematic diagram for explaining an example of the display device in embodiment 10 Schematic diagram for explaining another example of the display device in embodiment 10

[0011] First Embodiment Hereinafter, a first embodiment will be described with reference to the drawings. In the first embodiment, an optical system applied to a head-mounted display will be described as an example of a projection-type image display device.

[0012] 1 and 2. Fig. 1 is a schematic diagram for explaining an optical system 1 according to the first embodiment.

[0013] 1, the optical system 1 includes an illumination optical system 2, a first projection optical system 3, and a second projection optical system 4. The illumination optical system 2 splits light from a light source 10 into multiple beams of light using a polarizing beam splitter (PBS) 20, aligns the polarization states of the multiple beams of light, and outputs the beams in two different directions. The first and second projection optical systems 3 and 4 receive the light output from the illumination optical system 2 and project an image onto a display screen.

[0014] In this embodiment, the illumination optical system 2 splits randomly polarized light L0 from the light source 10 into first light L1 and second light L2 using a polarizing beam splitter 20 and aligns the polarization states of the first light L1 and the second light L2. The illumination optical system 2 also outputs the first light L1 in a first direction and the second light L2 in a second direction different from the first direction. The first and second directions are directions that intersect with the direction in which the randomly polarized light L0 is output. Specifically, the first direction is the rightward direction, and the second direction is the leftward direction. The first projection optical system 3 is positioned in the first direction and receives the first light L1 to project an image. The second projection optical system 4 is positioned in the second direction and receives the second light L2 to project an image.

[0015] 2A and 2B are schematic diagrams illustrating a head-mounted display 100 including the optical system 1 of the first embodiment. FIG. 2A shows a perspective view of an example of the head-mounted display 100. FIG. 2B shows an example of the internal structure of the head-mounted display 100 in a plan view. As shown in FIGS. 2A and 2B , the optical system 1 is applied to the head-mounted display 100. The head-mounted display 100 includes the optical system 1, a housing frame 5, a first light guiding device 6, and a second light guiding device 7. The head-mounted display 100 also includes a first display screen viewing area 8 and a second display screen viewing area 9. The first display screen viewing area 8 and the second display screen viewing area 9 are located in areas where the user's eyes are located. The first light guiding device 6 and the second light guiding device 7, for example, guide image light from the first projection optical system 3 and the second projection optical system 4 to the first display screen viewing area 8 and the second display screen viewing area 9, i.e., guide the light to the user's eyes. Furthermore, the first light guide device 6 and the second light guide device 7 may be configured, for example, as a light guide plate having a diffraction structure on a transmissive optical material, so as to superimpose the external world and the image. When the first light guide device 6 and the second light guide device 7 are configured as light guide plates having a diffraction grating, the first light guide device 6 and the second light guide device 7 can efficiently guide light of a specific polarization state guided from the first projection optical system 3 and the second projection optical system 4 to the user's eyes as image light.

[0016] The housing frame 5 is a frame in the shape of glasses. For example, the housing frame 5 includes a front frame 5 a and support frames 5 b extending from both sides of the front frame 5 a. When the head-mounted display 100 is worn by a user, the front frame 5 a is placed in front of the user's eyes, and the support frames 5 b are supported by the user's ears.

[0017] The optical system 1 is housed inside the center of the front frame 5a. A first light guiding device 6 and a second light guiding device 7 are also arranged in the front frame 5a with the optical system 1 sandwiched therebetween. When the head-mounted display 100 is worn by a user, the first display screen visible area 8 and the second display screen visible area 9 are located in front of the user's eyes.

[0018] The first light-guiding device 6 receives the image light projected from the first projection optical system 3. The second light-guiding device 7 receives the image light projected from the second projection optical system 4.

[0019] Image light is projected from the first light-guiding device 6 onto the first display screen viewing region 8, and the user can view the display screen without any omissions when the user's eyes are within the first display screen viewing region 8. Image light is projected from the second light-guiding device 7 onto the second display screen viewing region 9, and the user can view the display screen without any omissions when the user's eyes are within the second display screen viewing region 9.

[0020] As described above, the head mounted display 100 includes a first projection optical system 3 that projects an image for the user's right eye, and a second projection optical system 4 that projects an image for the user's left eye, to which the optical system 1 projects light. The head mounted display 100 also includes a first light guiding device 6 that guides the image light projected by the first projection optical system 3 to the user's eye, and a second light guiding device 7 that guides the image light projected by the second projection optical system 4 to the user's eye.

[0021] The head-mounted display 100 may also include a so-called pupil-widening light guide. The light guide may be capable of duplicating a single incident light beam into multiple light beams of image light, and may duplicate the light beam in a first light beam direction and a second light beam direction to expand the display image viewing areas 8, 9. The user can view each of the multiple light beams of image light as a virtual image Iv, thereby widening the display image viewing areas 8, 9 in which the user can view the image light.

[0022] For example, the pupil widening type light guide may include a coupling region that receives the image light from the first light guide device 6 and the second light guide device 7 and changes the traveling direction of the image light, a first widening region that widens the image light in a first light flux direction, and a second widening region that widens the image light in a second light flux direction. The first light flux direction and the second light flux direction may intersect with each other, for example, be perpendicular to each other.

[0023] The coupling region, the first extension region, and the second extension region each have a diffraction power for diffracting the image light, and may have a diffractive structure element such as an embossed hologram or a volume hologram formed therein. The embossed hologram is, for example, a diffraction grating. The volume hologram is, for example, a periodic refractive index distribution in a dielectric film.

[0024] For example, the coupling region may change the traveling direction of image light incident from outside to head toward the first expansion region by using diffraction power. The first expansion region may have a diffractive structure element disposed therein, and may replicate the image light by splitting the incident image light into image light traveling in a first light beam direction and image light traveling toward the second expansion region by using diffraction power. The second expansion region may have a diffractive structure element disposed therein, and may replicate the image light by splitting the incident image light into image light traveling in a second light beam direction and image light exiting the second expansion region to the outside by using diffraction power.

[0025] It should be noted that the head mounted display 100 is not limited to the glasses type. For example, the head mounted display 100 may have no support frame and may be configured to be worn on the head.

[0026] The illumination optical system 2 will now be described in detail.

[0027] Returning to FIG. 1, the illumination optical system 2 includes a light source 10, a polarizing beam splitter 20, a reflecting element 30, a phase difference plate 31, a lens array element 40, and a lens element 50.

[0028] The light source 10 collimates and emits randomly polarized light L0. For example, the light source 10 converts randomly polarized light having an R (red) light component, a G (green) light component, and a B (blue) light component into substantially parallel light and emits the collimated light.

[0029] The light source 10 includes a light source element 11 and a collimator element 12 .

[0030] The light source element 11 generates randomly polarized light L0. The light source element 11 is a light emitting diode (LED) or the like, and the light source element 11 can also be collectively represented as a plurality of optical elements.

[0031] The collimator element 12 collimates the randomly polarized light L0 generated by the light source element 11. The collimator element 12 converts the randomly polarized light L0 into substantially parallel light. For example, the collimator element 12 is a collimator lens.

[0032] The collimator element 12 may be composed of a plurality of lenses. Furthermore, the collimator element 12 is not limited to a collimator lens. The collimator element 12 may be any optical element that can collimate the randomly polarized light L0. For example, the collimator element 12 may be an optical element such as a mirror, or may be a diffractive optical element.

[0033] Randomly polarized light L 0 emitted from the light source 10 passes through the lens array element 40 and the lens element 50 and enters the polarizing beam splitter 20 .

[0034] The lens array element 40 is an optical element in which a plurality of lens elements are arranged on a substrate. The lens array element 40 is disposed between the light source 10 and the polarizing beam splitter 20. The lens array element 40 splits the randomly polarized light L0 emitted from the light source 10 into a plurality of secondary light source lights.

[0035] The lens element 50 is a lens that condenses the plurality of secondary light source light beams. The lens element 50 is, for example, a relay lens. The lens element 50 condenses the plurality of secondary light source light beams split by the lens array element 40.

[0036] The polarizing beam splitter 20 splits the randomly polarized light L0 into a first light L1 and a second light L2, guides the first light L1 in a first direction, and guides the second light L2 in a second direction. The polarizing beam splitter 20 includes a splitting surface 21 that splits the randomly polarized light L0 into the first light L1 and the second light L2.

[0037] The splitting surface 21 reflects the first polarized light and transmits the second polarized light. The splitting surface 21 splits the randomly polarized light L0 into a first light L1 having a first polarization state obtained by reflecting the first polarized light from the randomly polarized light L0, and a second light L2 having a second polarization state obtained by transmitting the second polarized light from the randomly polarized light L0. The splitting surface 21 is provided inside the polarizing beam splitter 20.

[0038] In this embodiment, the first polarized light is S-polarized light, and the second polarized light is P-polarized light. The first polarization state is formed by S-polarized light, and the second polarization state is formed by P-polarized light. The first polarized light and the second polarized light are linearly polarized light.

[0039] The polarizing beam splitter 20 has a cube shape. For example, the polarizing beam splitter 20 has first to fourth surfaces PS1 to PS4 in a cross section including the light source 10, the first projection optical system 3, and the second projection optical system 4. The first surface PS1 faces the third surface PS3, and the second surface PS2 faces the fourth surface PS4. Furthermore, the first surface PS1 and the third surface PS3 are perpendicular to the second surface PS2 and the fourth surface PS4.

[0040] A light source 10, a lens array element 40, and a lens element 50 are arranged on the first surface PS1 side of the polarizing beam splitter 20. A first projection optical system 3 is arranged on the second surface PS2 side. A reflecting element 30 and a retardation plate 31 are arranged on the third surface PS3 side. A second projection optical system 4 is arranged on the fourth surface PS4 side.

[0041] The first surface PS1 of the polarizing beam splitter 20 is an entrance surface onto which the randomly polarized light L0 from the light source 10 is incident. The second surface PS2 is an exit surface from which the first light L1 is emitted. The third surface PS3 is a surface onto which the second light L2 is emitted and incident. The fourth surface PS4 is an exit surface from which the second light L2 is emitted.

[0042] The reflecting element 30 is an optical element that reflects light. The reflecting element 30 has a reflecting surface 32 that reflects light. The reflecting element 30 is disposed on the optical path of the second light L2 that has passed through the splitting surface 21, on the third surface PS3 side of the polarizing beam splitter 20. The reflecting element 30 is disposed away from the third surface PS3 of the polarizing beam splitter 20 and is disposed close to the retardation plate 31. For example, the reflecting element 30 is disposed within a range of 0.05 mm to 2.0 mm from the retardation plate 31.

[0043] The reflecting surface 32 reflects the second light L2 branched from the branching surface 21. Specifically, the reflecting surface 32 reflects the second light L2 and guides it to the branching surface 21 again.

[0044] The reflecting surface 32 is provided on the side of the reflecting element 30 that faces the third surface PS3 of the polarizing beam splitter 20.

[0045] For example, the reflective element 30 may be a mirror or a lens having a curved surface.

[0046] The retardation plate 31 changes the polarization state of polarized light. The retardation plate 31 is an optical element that changes the polarization state by imparting a predetermined phase difference to polarized light. The retardation plate 31 is disposed between the polarizing beam splitter 20 and the reflecting element 30.

[0047] The retardation plate 31 is disposed in close contact with the polarizing beam splitter 20. Specifically, the retardation plate 31 is disposed on the third surface PS3 of the polarizing beam splitter 20.

[0048] The retardation plate 31 is a quarter-wave plate that imparts a phase difference of λ / 4 to the electric field oscillation direction of the polarized light.

[0049] The retardation plate 31 changes the second light L2 from the second polarization state to the first polarization state. The second light L2 passes from the splitting surface 21 through the retardation plate 31, enters the reflecting surface 32, and is reflected by the reflecting surface 32. The second light L2 reflected by the reflecting surface 32 passes through the retardation plate 31 and enters the splitting surface 21. In this way, a phase difference of λ / 2 is given to the second light L2 by passing through the retardation plate 31 twice. This changes the second light L2 from the second polarization state to the first polarization state.

[0050] The retardation plate 31 is not limited to a quarter-wave plate. The retardation plate 31 may be any plate that provides a phase difference to change the second light L2 from the second polarization state to the first polarization state. For example, the retardation plate 31 may be composed of two eighth-wave plates or four sixteenth-wave plates. Furthermore, the retardation plate 31 may provide a phase difference of 0.24×λ to 0.26×λ in the electric field oscillation direction of the polarized light.

[0051] The first projection optical system 3 is disposed on the second surface PS2 side of the polarizing beam splitter 20. The first projection optical system 3 is disposed at a position a first distance D1 away from the second surface PS2 of the polarizing beam splitter 20. The first distance D1 is the distance between the polarizing beam splitter 20 and the first projection optical system 3. Specifically, the first distance D1 is the distance from the second surface PS2 of the polarizing beam splitter 20 to the optical element that is disposed closest to the second surface PS2 among the optical elements that make up the first projection optical system 3.

[0052] The second projection optical system 4 is disposed on the side of the fourth surface PS4 of the polarizing beam splitter 20 that emits the second light L2. The second projection optical system 4 is disposed at a position a second distance D2 away from the fourth surface PS4 of the polarizing beam splitter 20. The second distance D2 is the distance between the polarizing beam splitter 20 and the second projection optical system 4. Specifically, the second distance D2 is the distance from the fourth surface PS4 of the polarizing beam splitter 20 to the optical element that is disposed closest to the fourth surface PS4 among the optical elements that make up the second projection optical system 4.

[0053] The first distance D1 and the second distance D2 are set so that the first light L1 incident on the first projection optical system 3 and the second light L2 incident on the second projection optical system 4 have approximately the same luminance distribution. Specifically, the first distance D1 and the second distance D2 are set so that the length of the optical path from the light emitted from the lens element 50 to the first projection optical system 3 is approximately the same as the length of the optical path from the light emitted from the lens element 50 to the second projection optical system 4.

[0054] Within the polarizing beam splitter 20, the first light L1 is reflected by the splitting surface 21 and then exits from the second surface PS2. Meanwhile, the second light L2 passes through the splitting surface 21, is reflected by the reflecting surface 32, and is further reflected by the splitting surface 21 before exiting from the fourth surface PS4. Thus, within the polarizing beam splitter 20, the optical path of the second light L2 is longer than the optical path of the first light L1. For this reason, by setting the second distance D2 to be smaller than the first distance D1, the first light L1 incident on the first projection optical system 3 and the second light L2 incident on the second projection optical system 4 can have substantially the same luminance distribution.

[0055] [1-2. Operation of the Optical System] Next, the operation of the optical system 1 will be described.

[0056] Collimated randomly polarized light L0 is emitted from the light source 10. The randomly polarized light L0 is split into a plurality of secondary light source beams by the lens array element 40. The plurality of secondary light source beams are collected by the lens element 50 and enter the first surface PS1 of the polarizing beam splitter 20.

[0057] In the polarizing beam splitter 20, randomly polarized light L0 is incident on the splitting surface 21, where it is split into a first light L1 having a first polarization state and a second light L2 having a second polarization state. The splitting surface 21 reflects the first polarized light of the randomly polarized light L0 and transmits the second polarized light. The first polarized light of the randomly polarized light L0 is reflected by the splitting surface 21, thereby obtaining the first light L1 having the first polarization state. The second polarized light of the randomly polarized light L0 is transmitted through the splitting surface 21, thereby obtaining the second light L2 having the second polarization state.

[0058] The first light L1 is guided by the splitting surface 21 in a first direction intersecting the incident direction of the randomly polarized light L0. The first light L1 is guided from the splitting surface 21 toward the second surface PS2 and is emitted from the second surface PS2. The first light L1 emitted from the second surface PS2 is incident on the first projection optical system 3. The first projection optical system 3 receives the first light L1 and projects an image.

[0059] The second light L2 passes from the splitting surface 21 through the retardation plate 31 arranged on the third surface PS3 and is incident on the reflecting surface 32 of the reflecting element 30. At this time, a phase difference of λ / 4 is given to the second light L2 by passing through the retardation plate 31. The second light L2 is reflected by the reflecting surface 32, passes through the retardation plate 31 again, and is incident on the splitting surface 21. At this time, a phase difference of λ / 4 is further given to the second light L2 by passing through the retardation plate 31.

[0060] In this way, a phase difference of λ / 2 is given to the second light L2 by passing twice through the retardation plate 31. As a result, the second light L2 is changed from the second polarization state to the first polarization state.

[0061] The second light L2 in the first polarization state is reflected by the splitting surface 21 and guided in a second direction opposite to the first direction. The second light L2 is guided from the splitting surface 21 toward the fourth surface PS4 and is emitted from the fourth surface PS4. The second light L2 emitted from the fourth surface PS4 is incident on the second projection optical system 4. The second projection optical system 4 receives the second light L2 and projects an image.

[0062] [2. Effects, etc.] As described above, the optical system 1 includes a light source 10, a polarizing beam splitter 20, a reflecting element 30, and a retardation plate 31. The light source 10 collimates and emits randomly polarized light L0. The polarizing beam splitter 20 includes a splitting surface 21 that splits the randomly polarized light L0 into a first light L1 having a first polarization state obtained by reflecting a first polarized portion of the randomly polarized light L0, and a second light L2 having a second polarization state obtained by transmitting a second polarized portion of the randomly polarized light L0. The reflecting element 30 includes a reflecting surface 32 that reflects the second light L2 split from the splitting surface 21. The retardation plate 31 is disposed between the polarizing beam splitter 20 and the reflecting element 30. The splitting surface 21 guides the first light L1 in a first direction. The retardation plate 31 changes the second light L2 from the second polarization state to the first polarization state. The splitting surface 21 reflects the second light L2 whose polarization state has been changed to the first polarization state and guides the light in a second direction different from the first direction.

[0063] This configuration makes it possible to achieve miniaturization while improving the light utilization efficiency of the light source 10. Specifically, the optical system 1 splits randomly polarized light L0 from the light source 10 into a first light L1 having a first polarization state and a second light L2 having a second polarization state by the splitting surface 21 of the polarizing beam splitter 20. The first light L1 is guided by the splitting surface 21 and output in a first direction, and the second light L2 is changed from the second polarization state to the first polarization state by the reflecting element 30 and the retardation plate 31. The second light L2 changed to the first polarization state is guided by the splitting surface 21 and output in a second direction.

[0064] Generally, an optical system that outputs two light beams with aligned polarization states uses two light sources. This can make it difficult to miniaturize the optical system. In the optical system 1 of this embodiment, randomly polarized light L0 from a single light source 10 is split into first light L1 and second light L2, which are output with aligned polarization states. Because the light source 10 can be shared to output the first light L1 and the second light L2, the optical system 1 can be miniaturized while improving the light utilization efficiency of the light source 10. Furthermore, the manufacturing cost of the optical system 1 can be reduced.

[0065] Furthermore, in the optical system 1, the polarization state of the second light L2 is changed to be the same as that of the first light L1 using a reflecting element 30 and a retardation plate 31. This improves the light utilization efficiency of the light source 10. Note that, in general, in optical systems that split random light using a polarizing beam splitter, most of the light that enters the projection optical system is extracted and the other light is discarded. In the optical system 1 of this embodiment, the second light L2 is not discarded, but is utilized by changing its polarization state, thereby improving the light utilization efficiency.

[0066] The retardation plate 31 is a quarter-wave plate. With this configuration, the polarization state of the second light L2 can be changed with a simpler configuration, and therefore the optical system 1 can be made more compact.

[0067] The first light L1 is incident on the first projection optical system 3, and the second light L2 is incident on the second projection optical system 4. With this configuration, the first projection optical system 3 can receive the first light L1 and project an image, and the second projection optical system 4 can receive the second light L2 and project an image. This allows two images to be displayed on a display screen or the like.

[0068] The first projection optical system 3 is disposed a first distance D1 away from the second surface PS2 of the polarizing beam splitter 20. The second surface PS2 of the polarizing beam splitter 20 is the exit surface for the first light L1. The second projection optical system 4 is disposed a second distance D2 away from the fourth surface PS4 of the polarizing beam splitter 20. The fourth surface PS4 of the polarizing beam splitter 20 is the exit surface for the second light L2. The second distance D2 is smaller than the first distance D1.

[0069] With this configuration, the first light L1 incident on the first projection optical system 3 and the second light L2 incident on the second projection optical system 4 have approximately the same luminance distribution. That is, the luminance distributions of the first light L1 and the second light L2 are made uniform.

[0070] The optical system 1 includes a lens array element 40 that splits light into a plurality of secondary light source beams, and a lens element 50 that condenses the plurality of secondary light source beams from the lens array element 40. With this configuration, the luminance distribution of the first light L1 and the second light L2 that enter the first projection optical system 3 and the second projection optical system 4 can be made uniform.

[0071] The lens array element 40 is disposed between the light source 10 and the polarizing beam splitter 20. With this configuration, the luminance distribution of the first light L1 and the second light L2 can be made more uniform, and the optical system 1 can be made smaller.

[0072] The lens element 50 is disposed between the lens array element 40 and the polarizing beam splitter 20. With this configuration, the luminance distribution of the first light L1 and the second light L2 can be made more uniform, while the optical system 1 can be made smaller.

[0073] The retardation plate 31 is disposed in close contact with the polarizing beam splitter 20. With this configuration, the optical system 1 can be made compact while suppressing deterioration of the retardation plate 31.

[0074] The light source 10 includes a light source element 11 that generates randomly polarized light L0 and a collimator element 12 that collimates the randomly polarized light L0 generated by the light source element 11. With this configuration, the optical system 1 can be made compact while easily emitting collimated light.

[0075] The head mounted display 100 includes the above-described optical system 1. With this configuration, it is possible to achieve the same effects as those of the above-described optical system 1.

[0076] Second Embodiment An optical system 1A according to a second embodiment will be described with reference to Fig. 3. Fig. 3 is a schematic diagram for explaining the optical system 1A according to the second embodiment.

[0077] In the optical system 1A of the second embodiment, a first lens element 51 that collects the first light L1 is disposed on the optical path of the first light L1 emitted from the polarizing beam splitter 20. Furthermore, a second lens element 52 that collects the second light L2 is disposed on the optical path of the second light L2 emitted from the polarizing beam splitter 20. Note that no lens element is disposed between the lens array element 40 and the polarizing beam splitter 20. With respect to the configuration of the optical system 1A of the second embodiment, apart from these points and points that will be described below, the optical system 1A of the second embodiment is common to the optical system 1 of the first embodiment.

[0078] As shown in FIG. 3, the illumination optical system 2A of the optical system 1A includes a first lens element 51 and a second lens element 52.

[0079] The first lens element 51 is disposed on the optical path of the first light L1 emitted from the polarizing beam splitter 20. The first lens element 51 is disposed between the polarizing beam splitter 20 and the first projection optical system 3. The first lens element 51 condenses the first light L1.

[0080] The second lens element 52 is disposed on the optical path of the second light L2 emitted from the polarizing beam splitter 20. The second lens element 52 is disposed between the polarizing beam splitter 20 and the second projection optical system 4. The second lens element 52 condenses the second light L2.

[0081] For example, the first lens element 51 and the second lens element 52 are relay lenses having the same refractive power.

[0082] Even in this configuration, the first light L1 incident on the first projection optical system 3 can be collected by the first lens element 51, thereby making the luminance distribution of the first light L1 uniform. Also, the second light L2 incident on the second projection optical system 4 can be collected by the second lens element 52, thereby making the luminance distribution of the second light L2 uniform.

[0083] Furthermore, since the first lens element 51 and the second lens element 52 are the same lens, it is possible to use common components.

[0084] Third Embodiment An optical system 1B according to a third embodiment will be described with reference to Fig. 4. Fig. 4 is a schematic diagram for explaining the optical system 1B according to the third embodiment.

[0085] In optical system 1B of embodiment 3, first lens element 51 and second lens element 52 are different relay lenses, and first distance D1 is made small. Except for this point and points described below, optical system 1B of embodiment 3 has the same configuration as optical system 1A of embodiment 2.

[0086] 4 , illumination optical system 2B of optical system 1B includes first lens element 51 and second lens element 52. Different relay lenses are used for first lens element 51 and second lens element 52. For example, the refractive power of first lens element 51 is greater than the refractive power of second lens element 52.

[0087] With this configuration, the first light L1 incident on the first projection optical system 3 is condensed by the first lens element 51, thereby making it possible to uniformize the luminance distribution of the first light L1. Also, the second light L2 incident on the second projection optical system 4 is condensed by the second lens element 52, thereby making it possible to uniformize the luminance distribution of the second light L2.

[0088] Furthermore, by making the refractive power of the first lens element 51 greater than the refractive power of the second lens element 52, the first distance D1 can be reduced to the same as the second distance D2, thereby enabling the optical system 1A to be made even more compact.

[0089] Fourth Embodiment An optical system 1C according to a fourth embodiment will be described with reference to Fig. 5. Fig. 5 is a schematic diagram for explaining the optical system 1C according to the fourth embodiment.

[0090] In the optical system 1C of the fourth embodiment, a first lens element 51 that collects the first light L1 is disposed on the optical path of the first light L1 emitted from the polarizing beam splitter 20. In addition, a second lens element 52 that collects the second light L2 is disposed on the optical path of the second light L2 emitted from the polarizing beam splitter 20. With respect to the configuration of the optical system 1C of the fourth embodiment, other than these points and points described below, the optical system 1C of the fourth embodiment is the same as the optical system 1 of the first embodiment.

[0091] As shown in FIG. 5, an illumination optical system 2C of an optical system 1C includes a first lens element 51 and a second lens element 52.

[0092] The first lens element 51 is disposed on the optical path of the first light L1 emitted from the polarizing beam splitter 20. The first lens element 51 is disposed between the polarizing beam splitter 20 and the first projection optical system 3. The first lens element 51 condenses the first light L1.

[0093] The second lens element 52 is disposed on the optical path of the second light L2 emitted from the polarizing beam splitter 20. The second lens element 52 is disposed between the polarizing beam splitter 20 and the second projection optical system 4. The second lens element 52 condenses the second light L2.

[0094] For example, the first lens element 51 and the second lens element 52 are relay lenses. Different relay lenses are used for the first lens element 51 and the second lens element 52. For example, the refractive power of the first lens element 51 is greater than the refractive power of the second lens element 52.

[0095] With this configuration, the first light L1 incident on the first projection optical system 3 is condensed by the first lens element 51, thereby making the luminance distribution of the first light L1 more uniform. Also, the second light L2 incident on the second projection optical system 4 is condensed by the second lens element 52, thereby making the luminance distribution of the second light L2 more uniform.

[0096] Furthermore, by making the refractive power of the first lens element 51 greater than the refractive power of the second lens element 52, the first distance D1 between the polarizing beam splitter 20 and the first projection optical system 3 can be reduced to the same as the second distance D2, thereby making it possible to further miniaturize the optical system 1C.

[0097] Fifth Embodiment An optical system 1D according to a fifth embodiment will be described with reference to Fig. 6. Fig. 6 is a schematic diagram for explaining the optical system 1D according to the fifth embodiment.

[0098] In the optical system 1D of the fifth embodiment, a first lens array element 41 is disposed between the polarizing beam splitter 20 and the first lens element 51. Furthermore, a second lens array element 42 is disposed between the polarizing beam splitter 20 and the second lens element 52. Note that no lens array element is disposed between the light source 10 and the polarizing beam splitter 20. Apart from these points and points described below, the optical system 1D of the fifth embodiment has the same configuration as the optical system 1A of the second embodiment.

[0099] As shown in FIG. 6, the illumination optical system 2D of the optical system 1D includes a first lens array element 41 and a second lens array element 42.

[0100] The first lens array element 41 is disposed between the polarizing beam splitter 20 and the first lens element 51. The first lens array element 41 splits the first light L1 emitted from the polarizing beam splitter 20 into a plurality of secondary light source light beams. The plurality of secondary light source light beams are condensed by the first lens element 51 and enter the first projection optical system 3.

[0101] The second lens array element 42 is disposed between the polarizing beam splitter 20 and the second lens element 52. The second lens array element 42 splits the second light L2 emitted from the polarizing beam splitter 20 into a plurality of secondary light source light beams. The plurality of secondary light source light beams are condensed by the second lens element 52 and enter the second projection optical system 4.

[0102] With this configuration, the luminance distribution of the first light L1 incident on the first projection optical system 3 can be made more uniform by the first lens array element 41 and the first lens element 51. Also, the luminance distribution of the second light L2 incident on the second projection optical system 4 can be made more uniform by the second lens array element 42 and the second lens element 52.

[0103] (Other Embodiments of the Optical System) Hereinafter, other embodiments of the optical system will be exemplified.

[0104] In the above embodiment, an example has been described in which the light source light emitted from the light source 10 is randomly polarized. However, the light source light may be other light source light. For example, the light source light may be linearly polarized light including first and second polarized light components, light obtained by combining the first and second polarized light components, circularly polarized light, elliptically polarized light, or light obtained by combining these light components. In other words, the light source light may be light that includes the first and second polarized light components.

[0105] In the above embodiment, an example has been described in which the optical system 1 is applied to the head-mounted display 100. However, the optical system 1 may be applied to devices other than the head-mounted display 100. For example, the optical system 1 may be applied to a projection-type image display device such as a projector that projects two images.

[0106] In the above embodiment, an example has been described in which the polarizing beam splitter 20 is cubic in shape. However, the shape of the polarizing beam splitter 20 is not limited to a cube. For example, the polarizing beam splitter 20 may be plate-shaped. In this case, the first distance D1 may be the distance from the center of the splitting surface 21 to the first projection optical system 3, and the second distance D2 may be the distance from the center of the splitting surface 21 to the second projection optical system 4.

[0107] In the above embodiment, an example has been described in which the reflecting element 30 is disposed in proximity to the retardation film 31. However, as shown in FIG.

[0108] In the above embodiment, an example has been described in which the retardation plate 31 is disposed in close contact with the third surface PS3 of the polarizing beam splitter 20. However, as shown in Fig. 8, the retardation plate 31 may be disposed away from the polarizing beam splitter 20.

[0109] Alternatively, as shown in FIG. 9, the polarizing beam splitter 20, the reflecting element 30 and the retardation plate 31 may be arranged with a gap between them.

[0110] Even with such a configuration, the effects of the above-described embodiment can be achieved, and deterioration of the retardation film 31 can be further suppressed in some cases.

[0111] In the above embodiment, an example has been described in which the reflecting element 30 has a flat reflecting surface 32. However, the reflecting surface 32 of the reflecting element 30 may be configured as a curved surface.

[0112] 10, the reflecting element 30A may be, for example, a convex mirror, in which case the reflecting surface 32 may be formed as a convex curved surface.

[0113] 11, the reflecting element 30B may be, for example, a concave mirror, in which case the reflecting surface 32 may be formed as a concave curved surface.

[0114] 12, the reflecting element 30C may be, for example, a convex lens, in which case the reflecting surface 32 may be formed as a convex curved surface.

[0115] 13, the reflecting element 30D may be, for example, a concave lens, in which case the reflecting surface 32 may be formed as a concave curved surface.

[0116] 14 , in an illumination optical system 2E of an optical system 1E, an ND filter 60 may be provided on the optical path of the first light L1 emitted from the second surface PS2 of the polarizing beam splitter 20 until it enters the first projection optical system 3. The ND filter 60 is a neutral density filter used to reduce the amount of light entering the first projection optical system 3. With this configuration, it is possible to adjust the density of the ND filter 60 and make the amount of light entering the second projection optical system equal to the amount of light entering the first projection optical system.

[0117] 15 , in the illumination optical system 2F of the optical system 1F, a polarizer 70 that transmits specific linearly polarized light and a light-intensity adjusting retardation plate 80 may be provided on the optical path of the first light L1 emitted from the second surface PS2 of the polarizing beam splitter 20 until it enters the first projection optical system 3. It is desirable that the transmission axis of the polarizer 70 coincides with the polarization direction of the first light L1. With this configuration, it is possible to rotate the fast axis of the light-intensity adjusting retardation plate 80 with respect to the polarization axis of the first light L1, thereby adjusting the amount of light entering the first projection optical system.

[0118] Even with this configuration, the effects of the above-described embodiment can be achieved. Furthermore, the second distance D2 can be adjusted by devising the shape of the reflecting surface 32. Furthermore, the luminance distribution of the second light L2 can be made uniform.

[0119] In the above embodiment, an example has been described in which lens element 50, first lens element 51, and second lens element 52 each consist of a single lens. However, lens element 50, first lens element 51, and second lens element 52 may each consist of a plurality of lens elements. Furthermore, lens element 50, first lens element 51, and second lens element 52 may be made of a glass material or a resin material. Using a glass material improves reliability, while using a resin material can reduce costs.

[0120] Sixth Embodiment A display device 100A according to a sixth embodiment will be described with reference to Fig. 16. Fig. 16 is a schematic diagram for explaining the display device 100A according to the sixth embodiment.

[0121] A display device 100A in embodiment 6 includes an optical system 101A. The optical system 101A includes an illumination optical system 102, a first projection optical system 103, and a second projection optical system 104. The first projection optical system 103 and the second projection optical system 104 include a first display unit 90 and a second display unit 91, respectively, that display images. In embodiment 6, the configurations of the illumination optical system 102, the first projection optical system 103, and the second projection optical system 104 may be the same as those of the illumination optical systems 2 to 2F, the first projection optical system 3, and the second projection optical system 4 in embodiments 1 to 5 and other optical system embodiments, unless otherwise specified.

[0122] The illumination optical system 102 includes a light source 10 and a polarizing beam splitter 20, and splits randomly polarized light from the light source 10 into a first light having a first polarization state and a second light having a second polarization state by a splitting surface 21 of the polarizing beam splitter 20. The illumination optical system 2 outputs the first light in a first direction and outputs the second light in a second direction different from the first direction. The first direction is a direction intersecting the direction in which the randomly polarized light is output, and the second direction is the same direction as the direction in which the randomly polarized light is output.

[0123] In this embodiment, too, an example has been described in which the light source light emitted from the light source 10 is randomly polarized light. However, the light source light may be other light source light. For example, it may be linearly polarized light containing first and second polarized light components, light obtained by combining the first and second polarized light components, circularly polarized light, elliptically polarized light, or light obtained by combining these lights. In other words, the light source light may be light that includes the first and second polarized light components.

[0124] The light source 10 is disposed on the first surface PS1 side of the polarizing beam splitter 20. The first projection optical system 103 is disposed on the second surface PS2 side. The second projection optical system 104 is disposed on the third surface PS3 side. The first surface PS1 of the polarizing beam splitter 20 is an entrance surface onto which randomly polarized light L0 from the light source 10 is incident. The second surface PS2 is an exit surface from which the first light L1 is emitted. The third surface PS3 is an exit surface from which the second light L2 is emitted.

[0125] The illumination optical system 102 guides the first light to the first display unit 90 and the second light to the second display unit 91. For example, the first display unit 90 and the second display unit 91 may be liquid crystal displays or digital micromirror devices.

[0126] The first projection optical system 103 projects an image to be displayed on the first display unit 90 using first light. The second projection optical system 104 projects an image to be displayed on the second display unit using second light.

[0127] As described above, the display device 100A of the sixth embodiment includes a first projection optical system 103 having a first display unit 90 that displays an image, a second projection optical system 104 having a second display unit 91 that displays an image, and an illumination optical system 102 that guides light to the first projection optical system 103 and the second projection optical system 104. The illumination optical system 102 includes a light source 10 that collimates and emits light source light including a first polarized light and a second polarized light, and a polarizing beam splitter 20 that includes a splitting surface 21 that splits the light source light into a first light having a first polarization state and a second light having a second polarization state. The illumination optical system 102 guides the first light to the first display unit 90 and guides the second light to the second display unit 91. The first projection optical system 103 projects an image displayed on the first display unit 90 using the first light. The second projection optical system 104 projects the image displayed on the second display unit 91 using the second light.

[0128] This configuration makes it possible to achieve a compact size while improving the light utilization efficiency of the light source 10. Specifically, since the two projection optical systems 103 and 104 can be illuminated by a single illumination optical system 102, a compact display device 100A can be realized.

[0129] Seventh Embodiment A display device 100B according to a seventh embodiment will be described with reference to Fig. 17A. Fig. 17A is a schematic diagram for explaining the display device 100B according to the seventh embodiment.

[0130] In the display device 100B of the seventh embodiment, the optical system 101B includes at least one retardation plate 31. Except for these points and points described below, the display device 100B of the seventh embodiment has the same configuration as the display device 100A of the sixth embodiment.

[0131] The retardation plate 31 is disposed on the optical path between the splitting surface 21 of the polarizing beam splitter 20 and the second projection optical system 104. The retardation plate 31 changes the second light split by the splitting surface 21 from the second polarization state to the first polarization state.

[0132] The retarder 31 changes the second polarization state to the first polarization state by imparting a phase difference of λ / 2 to the second light. For example, when one retarder 31 is used, the retarder 31 is a half-wave plate. When two retarders 31 are used, each of the two retarders 31 is a quarter-wave plate.

[0133] The first projection optical system 103 and the second projection optical system 104 are configured to guide the polarized light that is incident thereon.

[0134] In this way, the display device 100B of embodiment 7 has at least one retardation plate 31 on the optical path between the splitting surface 21 and the second projection optical system 104, which changes the two lights split by the splitting surface 21 from the second polarization state to the first polarization state.

[0135] With this configuration, the second light guided to the second projection optical system 104 by at least one retardation plate 31 can be made to have the same polarization state as the first light guided to the first projection optical system 103. This allows the first projection optical system 103 and the second projection optical system 104 to share components.

[0136] In the case of a projection optical system that guides light in the first polarization state or the second polarization state, a configuration that guides the first light and the second light that are branched into the first polarization state and the second polarization state from the illumination optical system 102 can reduce light loss within the first and second projection optical systems 103 and 104. This makes it possible to configure a display device 100B that utilizes light efficiently.

[0137] FIG. 17B is a schematic diagram for explaining another example of the display device 100B according to the seventh embodiment.

[0138] 17B , the retardation plate 31 may be disposed on the optical path between the splitting surface 21 and the first projection optical system 103. In this case, the retardation plate 31 changes the first light split by the splitting surface 21 from the first polarization state to the second polarization state.

[0139] With this configuration, the first light guided to the first projection optical system 103 by at least one retardation plate 31 can be made to have the same polarization state as the second light guided to the second projection optical system 104. This allows the first projection optical system 103 and the second projection optical system 104 to share components.

[0140] FIG. 17C is a schematic diagram for explaining another example of the display device 100B according to the seventh embodiment.

[0141] As shown in Figure 17C, at least one or more first retardation plates 31A may be arranged on the optical path between the branching surface 21 and the second projection optical system 104, and at least one or more second retardation plates 31B may be arranged on the optical path between the branching surface 21 and the first projection optical system 103.

[0142] With this configuration, the first retardation plate 31A can change the second light from the second polarization state to the first polarization state, and the second retardation plate 31B can change the first light from the first polarization state to the second polarization state.

[0143] For example, in the display device 100B, if the first projection optical system 103 is configured to receive and project light in the second polarization state, the first light guided to the first projection optical system 103 can be changed to the second polarization state by the second retardation plate 31B. If the second projection optical system 104 is configured to receive and project light in the first polarization state, the second light guided to the second projection optical system 104 can be changed to the first polarization state by the first retardation plate 31A. That is, the polarization states of the first light and the second light can be changed depending on the configurations of the first and second projection optical systems 103 and 104.

[0144] Eighth Embodiment A display device 100C according to an eighth embodiment will be described with reference to Fig. 18A. Fig. 18A is a schematic diagram for explaining the display device 100C according to the eighth embodiment.

[0145] In the display device 100C of the eighth embodiment, the optical system 101C includes a reflecting element 30 and a retardation plate 31. The reflecting element 30 and the retardation plate 31 are disposed on the third surface PS3 side of the polarizing beam splitter 20. The second projection optical system 104 is disposed on the fourth surface PS4 side. Apart from these points and points described below, the display device 100C of the eighth embodiment has the same configuration as the display device 100B of the seventh embodiment.

[0146] The reflecting element 30 is disposed on the opposite side of the phase difference plate 31 from the splitting surface 21, and includes a reflecting surface 32 that reflects the second light split from the splitting surface 21. In this embodiment, the reflecting surface 32 is formed of a curved surface.

[0147] The retardation plate 31 changes the second light L2 from the second polarization state to the first polarization state. The second light L2 passes from the splitting surface 21 through the retardation plate 31, enters the reflecting surface 32, and is reflected by the reflecting surface 32. The second light L2 reflected by the reflecting surface 32 passes through the retardation plate 31 and enters the splitting surface 21. In this way, a phase difference of λ / 2 is given to the second light L2 by passing through the retardation plate 31 twice. This changes the second light L2 from the second polarization state to the first polarization state.

[0148] For example, when the optical system is configured with one retardation plate 31, the retardation plate 31 is a quarter-wave plate, and when the optical system is configured with two retardation plates 31, each of the two retardation plates 31 is a one-eighth-wave plate.

[0149] The second light changed to the first polarization state via the reflecting element 30 and the phase difference plate 31 is reflected by the branching surface 21 of the polarizing beam splitter 20, and is emitted from the fourth surface PS3 and guided to the second display section 91 of the second projection optical system 104.

[0150] Even in such a configuration, the configuration for guiding the first light and the second light split into the first polarization state and the second polarization state from the illumination optical system 102 can reduce the loss of light within the first and second projection optical systems 103 and 104. This makes it possible to configure the display device 100B that utilizes light efficiently.

[0151] FIG. 18B is a schematic diagram for explaining another example of the display device 100C according to the eighth embodiment.

[0152] As shown in Figure 18B, the display device 100C may be provided with at least one or more first phase difference plates 31A arranged on the third surface PS3 side of the polarizing beam splitter 20 and at least one or more second phase difference plates 31B arranged on the fourth surface PS4 side on the optical path between the splitting surface 21 and the second projection optical system 104.

[0153] The first retardation plate 31A and the second retardation plate 31B change the second polarization state to the first polarization state by imparting a phase difference of λ / 2 to the second light. For example, when configured with one first retardation plate 31A, the first retardation plate 31A is a quarter-wave plate. When configured with two first retardation plates 31A, each of the two first retardation plates 31A is a ⅛-wave plate. For example, when configured with one second retardation plate 31B, the second retardation plate 31B is a half-wave plate. When configured with two second retardation plates 31B, each of the two second retardation plates 31B is a quarter-wave plate.

[0154] The second light in the first polarization state emitted from the fourth surface PS4 of the polarizing beam splitter 20 may be changed to the second polarization state by the second retardation plate 31B and guided to the second display unit 91 of the second projection optical system 104. The second projection optical system 104 may guide the incident second light in the second polarization state.

[0155] FIG. 18C is a schematic diagram for explaining another example of the display device 100C according to the eighth embodiment.

[0156] As shown in Figure 18C, the display device 100C may include at least one or more first phase difference plates 31A arranged on the second surface PS2 side of the polarizing beam splitter 20 on the optical path between the splitting surface 21 and the second projection optical system 104, and at least one or more third phase difference plates 31C arranged on the second surface PS2 side on the optical path between the splitting surface 21 and the first projection optical system 103.

[0157] The third retardation plate 31C changes the first polarization state to the second polarization state by imparting a phase difference of λ / 2 to the first light. For example, when one third retardation plate 31C is used, the third retardation plate 31C is a half-wave plate. When two third retardation plates 31C are used, each of the two third retardation plates 31C is a quarter-wave plate.

[0158] The first light in the first polarization state emitted from the second surface PS2 of the polarizing beam splitter 20 may be changed to the second polarization state by the third retardation plate 31C and guided to the first display unit 90 of the first projection optical system 103. The first projection optical system 103 may guide the incident first light in the second polarization state.

[0159] FIG. 18D is a schematic diagram for explaining another example of the display device 100C according to the eighth embodiment.

[0160] As shown in FIG. 18D, the display device 100C may include at least one or more first retardation plates 31A, at least one or more second retardation plates 31B, and at least one or more third retardation plates 31C.

[0161] Even in such a configuration, the configuration for guiding the first light and the second light split into the first polarization state and the second polarization state from the illumination optical system 102 can reduce the loss of light within the first and second projection optical systems 103 and 104. This makes it possible to configure the display device 100C that utilizes light efficiently.

[0162] Ninth Embodiment A display device 100D according to a ninth embodiment will be described with reference to Fig. 19. Fig. 19 is a schematic diagram for explaining the display device 100D according to the ninth embodiment.

[0163] In the optical system 101D of the display device 100D of the ninth embodiment, the first display unit 90A and the second display unit 91A in the first projection optical system 103 and the second projection optical system 104 are liquid crystal displays. Except for these points and points described below, the display device 100D of the ninth embodiment has the same configuration as the display device 100C of the eighth embodiment.

[0164] In the display device 100D, the first light in the first polarization state split by the splitting surface 21 is emitted from the second surface PS2 of the polarizing beam splitter 20, reflected by the mirror 110A, and incident on the first display unit 90A of the first projection optical system 103.

[0165] The second light in the second polarization state split by splitting surface 21 is emitted from third surface PS3 of polarizing beam splitter 20, passes through reflective element 30 and retardation plate 31 to be changed to the first polarization state, is reflected by splitting surface 21, and is emitted from fourth surface PS4. The second light emitted from fourth surface PS4 is reflected by mirror 110B and enters second display unit 91A of second projection optical system 104.

[0166] The first display unit 90A and the second display unit 91A are liquid crystal displays that guide the polarized light of incident light. The liquid crystal displays may be either transmissive or reflective.

[0167] Specifically, the first display unit 90A guides a first light having a first polarization state, and the second display unit 91A guides a second light having a first polarization state. For example, images displayed on the first display unit 90A and the second display unit 91A are projected through the lens elements 111A and 111B.

[0168] As described above, in the display device 100D of the eighth embodiment, the first display unit 90A and the second display unit 91A are liquid crystal displays that guide the polarized light of incident light.

[0169] With this configuration, the first projection optical system 103 and the second projection optical system 104 can be constructed inexpensively.

[0170] In the present embodiment, the display device 100D is described as including the mirrors 110A and 110B. However, the mirrors 110A and 110B are not essential components.

[0171] In the present embodiment, the first display unit 90A and the second display unit 91A guide light in the first polarization state. However, the first display unit 90A and the second display unit 91A may guide light in the second polarization state.

[0172] (Embodiment 10) A display device 100E according to embodiment 10 will be described with reference to Fig. 20A. Fig. 20A is a schematic diagram for explaining the display device 100E according to embodiment 10.

[0173] In an optical system 101E of a display device 100E according to the tenth embodiment, a first projection optical system 103 and a second projection optical system 104 include polarizing beam splitters 20A and 20B. Except for these points and points described below, the display device 100E according to the tenth embodiment has the same configuration as the display device 100C according to the eighth embodiment.

[0174] The first projection optical system 103 includes a first polarizing beam splitter 20A, a first display unit 90, and a first lens 111A.

[0175] The first polarizing beam splitter 20A has first to fourth surfaces PS1 to PS4. The first display unit 90 is disposed on the first surface PS1 side of the first polarizing beam splitter 20A. The first display unit 90 and the first lens 111A are disposed on the third surface PS3 side of the first polarizing beam splitter 20A.

[0176] The first light in the first polarization state emitted from the second surface PS2 of the polarizing beam splitter 20 of the illumination optical system 102 enters the first projection optical system 103. The first light enters the fourth surface PS4 of the first polarizing beam splitter 20A, is reflected by the splitting surface 21, and exits from the first surface PS1. The first light exiting from the first surface PS1 enters the first display unit 90. The first display unit 90 converts the first light in the first polarization state into image light in the second polarization state and reflects it. The image light converted by the first display unit 90 enters the first surface PS1 of the first polarizing beam splitter 20A, transmits through the splitting surface 21, and exits from the third surface PS3. The image light exiting from the third surface PS3 is projected via the first lens 111A.

[0177] The second projection optical system 104 includes a second polarizing beam splitter 20B, a second display unit 91, and a second lens 111B.

[0178] The second polarizing beam splitter 20B has first to fourth surfaces PS1 to PS4. The second display unit 91 is disposed on the first surface PS1 side of the second polarizing beam splitter 20B. The second display unit 91 and the second lens 111B are disposed on the third surface PS3 side of the second polarizing beam splitter 20B.

[0179] The second light in the first polarization state emitted from the fourth surface PS4 of the polarizing beam splitter 20 of the illumination optical system 102 enters the second projection optical system 104. The second light enters the second surface PS2 of the second polarizing beam splitter 20B, is reflected by the splitting surface 21, and exits from the first surface PS1. The second light exiting from the first surface PS1 enters the second display unit 91. The second display unit 91 converts the second light in the first polarization state into image light in the second polarization state and reflects it. The image light converted by the second display unit 91 enters the first surface PS1 of the second polarizing beam splitter 20B, transmits through the splitting surface 21, and exits from the third surface PS3. The image light exiting from the third surface PS3 is projected via the second lens 111B.

[0180] Thus, in the display device 100E of embodiment 10, the first projection optical system 103 and the second projection optical system 104 are equipped with a first polarizing beam splitter 20A and a second polarizing beam splitter 20B that guide the polarized light of the incident light.

[0181] With this configuration, it is possible to adjust the optical path lengths of the first projection optical system 103 and the second projection optical system 104 while preventing the first projection optical system 103 and the second projection optical system 104 from becoming larger. Furthermore, it is possible to separately utilize the light incident on the first display unit 90 and the light emitted from the first display unit 90 while maintaining the same axis. Similarly, it is possible to separately utilize the light incident on the second display unit 91 and the light emitted from the second display unit 91 while maintaining the same axis.

[0182] FIG. 20B is a schematic diagram for explaining another example of the display device 100E according to the tenth embodiment.

[0183] 20B , the splitting surfaces 21 of the first polarizing beam splitter 20A and the second polarizing beam splitter 20B may transmit light in a first polarization state and reflect light in a second polarization state. In this case, the first display unit 90 may be disposed on the second surface PS2 of the first polarizing beam splitter 20A. The second display unit 91 may be disposed on the fourth surface PS4 of the second polarizing beam splitter 20B.

[0184] In the first projection optical system 103, the first light in the first polarization state emitted from the illumination optical system 102 enters the fourth surface PS4 of the first polarizing beam splitter 20A, passes through the splitting surface 21, and exits from the second surface PS2. The first light exiting from the second surface PS2 enters the first display unit 90. The first display unit 90 converts the first light in the first polarization state into image light in the second polarization state and reflects it. The image light converted by the first display unit 90 enters the second surface PS2 of the first polarizing beam splitter 20A, is reflected by the splitting surface 21, and exits from the third surface PS3.

[0185] In the second projection optical system 104, the second light in the first polarization state emitted from the illumination optical system 102 enters the second polarizing beam splitter 20B through the third surface PS3, passes through the splitting surface 21, and exits through the fourth surface PS4. The second light exiting through the fourth surface PS4 enters the second display unit 91. The second display unit 91 converts the second light in the first polarization state into image light in the second polarization state and reflects it. The image light converted by the second display unit 91 enters the second polarizing beam splitter 20B through the fourth surface PS4, is reflected by the splitting surface 21, and exits through the third surface PS3.

[0186] Even with this configuration, it is possible to adjust the optical path lengths of the first projection optical system 103 and the second projection optical system 104 while preventing the first projection optical system 103 and the second projection optical system 104 from becoming larger. Furthermore, it is possible to separately utilize the light incident on the first display unit 90 and the light emitted from the first display unit 90 while maintaining the same axis. Similarly, it is possible to separately utilize the light incident on the second display unit 91 and the light emitted from the second display unit 91 while maintaining the same axis.

[0187] In this embodiment, the first display unit 90 and the second display unit 91 are realized by, for example, a reflective liquid crystal display, or may be realized by a digital micromirror device and a wave plate.

[0188] As described above, the above embodiments have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to these embodiments and may be applied to embodiments in which modifications, substitutions, additions, omissions, combinations, etc. are made as appropriate.

[0189] It should be noted that, in this specification, terms such as "first," "second," etc. are used for descriptive purposes only and should not be understood as expressing or implying relative importance or ranking of technical features. Features qualified as "first" and "second" expressly or imply the inclusion of one or more of such features.

[0190] (Summary of Embodiments) (1) A display device of the present disclosure includes a first projection optical system having a first display unit that displays an image, a second projection optical system having a second display unit that displays an image, and an illumination optical system that guides light to the first projection optical system and the second projection optical system, wherein the illumination optical system has a light source that collimates and emits light source light including a first polarization and a second polarization, and a polarizing beam splitter that includes a splitting surface that splits the light source light into a first light having a first polarization state and a second light having a second polarization state, and the illumination optical system guides the first light to the first display unit and the second light to the second display unit, the first projection optical system projects an image displayed on the first display unit using the first light, and the second projection optical system projects an image displayed on the second display unit using the second light.

[0191] (2) The display device of (1) may further include at least one retardation plate on the optical path between the splitting surface and the second projection optical system, which changes the second light split at the splitting surface from the second polarization state to the first polarization state.

[0192] (3) In the display device of (2), the illumination optical system may include a reflecting element on the opposite side of the splitting surface of at least one retardation plate, the reflecting element including a reflective surface that reflects the second light split from the splitting surface, wherein at least one or more retardation plates change the second light from the second polarization state to the first polarization state, and the splitting surface reflects the second light that has been changed to the first polarization state and guides it to the second display unit.

[0193] (4) In the display device of (1) or (3), the first projection optical system and the second projection optical system may guide incident light in the first polarization state or the second polarization state.

[0194] (5) In the display device of (4), the first display section and the second display section may be liquid crystal displays that guide incident polarized light.

[0195] (6) In the display device of (4) or (5), the first projection optical system and the second projection optical system may further include a polarizing beam splitter that guides the polarized light of the incident light.

[0196] (7) Any of the display devices of (1) to (6) may further include a first light-guiding device that guides light projected from the first projection optical system to a first region where the user's eyes are located, and a second light-guiding device that guides light projected from the second projection optical system to a second region where the user's eyes are located, and the first light-guiding device and the second light-guiding device may guide light of the polarization state of the incident light.

[0197] (8) In the display device of (3), the first projection optical system is positioned a first distance from the exit surface of the polarizing beam splitter for the first light, and the second projection optical system is positioned a second distance from the exit surface of the polarizing beam splitter for the second light, and the second distance may be smaller than the first distance.

[0198] (9) In any of the display devices of (3), the illumination optical system may further include a first lens element arranged on the optical path of the first light emitted from the polarizing beam splitter and focusing the first light, and a second lens element arranged on the optical path of the second light emitted from the polarizing beam splitter and focusing the second light, and the refractive power of the first lens element may be greater than the refractive power of the second lens element.

[0199] (10) In any of the display devices of (1) to (9), a lens array element that divides light emitted from the light source into a plurality of secondary light sources, and a lens element that collects the plurality of secondary light sources from the lens array element may be further provided.

[0200] (11) In the display device of (10), the lens array element may be disposed between the light source and the polarizing beam splitter.

[0201] (12) In the display device of (10) or (11), the lens element may include a first lens element arranged on the optical path of the first light emitted from the polarizing beam splitter and focusing the first light, and a second lens element arranged on the optical path of the second light emitted from the polarizing beam splitter and focusing the second light.

[0202] (13) In the display device of (12), the lens array element may include a first lens array element disposed between the polarizing beam splitter and the first lens element, and a second lens array element disposed between the polarizing beam splitter and the second lens element.

[0203] (14) In the display device of (3), the reflective surface may be a curved surface.

[0204] (15) In any of the display devices (1) to (14), the light source may include a light source element that generates source light, and a collimator element that collimates the source light generated by the light source element.

[0205] (16) In any of the display devices of (1) to (15), the display device may be a head-mounted display in which the first projection optical system projects an image for the user's right eye and the second projection optical system projects an image for the user's left eye.

[0206] (17) The optical system of the present disclosure is an optical system that guides light to a first display unit of a first projection optical system and a second display unit of a second projection optical system, and includes a light source that collimates and emits light source light including a first polarization and a second polarization, and a polarizing beam splitter that includes a splitting surface that splits the light source light into a first light of a first polarization state and a second light of the light source light of a second polarization state, and guides the first light to the first display unit and the second light to the second display unit.

[0207] The present disclosure is applicable to an optical system of a projection-type image display device that projects two images, such as a head-mounted display.

[0208] REFERENCE SIGNS LIST 1, 1A, 1B, 1C, 1D, 1E, 1F Optical system 2, 2A, 2B, 2C, 2D, 2E, 2F Illumination optical system 3 First projection optical system 4 Second projection optical system 5 Housing frame 6 First light guiding device 7 Second light guiding device 8 First display screen viewing area 9 Second display screen viewing area 10 Light source 11 Light source element 12 Collimator element 20, 20A, 20B Polarizing beam splitter 21 Splitting surface 30, 30A, 30B, 30C, 30D Reflecting element 31, 31A, 31B Retardation plate 32 Reflecting surface 40 Lens array element 41 First lens array element 42 Second lens array element 50 Lens element 51 First lens element 52 Second lens element 60 ND filter 70 Polarizer 80 Light intensity adjusting retardation plate 90, 90A First display unit 91, 91A Second display unit 100 Head mounted display 100A, 100B, 100C, 100D, 100E Display device 101A, 101B, 101C, 101D, 101E Optical system 102A, 102B, 102C, 102D, 102E Illumination optical system 103 First projection optical system 104 Second projection optical system 110A, 110B Mirror 111A, 111B Lens element D1 First distance D2 Second distance L0 Random polarization L1 First light L2 Second light PS1 First surface PS2 Second surface PS3 Third surface PS4 Fourth surface

Claims

1. a first projection optical system having a first display unit that displays an image; a second projection optical system having a second display unit that displays an image; an illumination optical system that guides light to the first projection optical system and the second projection optical system; Equipped with The illumination optical system includes: a light source that collimates and emits light source light including first and second polarized light; a polarizing beam splitter including a splitting surface that splits the light source light into a first light having a first polarization state and a second light having a second polarization state; and the illumination optical system guides the first light to the first display unit and guides the second light to the second display unit; the first projection optical system projects an image displayed on the first display unit using the first light, and the second projection optical system projects an image displayed on the second display unit using the second light. Display device.

2. and further comprising at least one retardation plate, which changes the second light split by the splitting surface from a second polarization state to the first polarization state, on an optical path between the splitting surface and the second projection optical system. The display device according to claim 1 .

3. the illumination optical system includes a reflecting element, on an opposite side of the splitting surface of the at least one retardation plate, including a reflecting surface that reflects the second light split from the splitting surface, the at least one retarder changes the second light from the second polarization state to the first polarization state; the splitting surface reflects the second light, which has been changed to the first polarization state, and guides the second light to the second display unit. The display device according to claim 2 .

4. the first projection optical system and the second projection optical system guide incident light in a first polarization state or a second polarization state; The display device according to claim 1 or 3.

5. the first display unit and the second display unit are liquid crystal displays that guide incident light in a polarization state; The display device according to claim 4 .

6. the first projection optical system and the second projection optical system further include a polarizing beam splitter that guides the polarized light of the incident light; The display device according to claim 4 .

7. a first light guiding device that guides light projected from the first projection optical system to a first area where a first eye of a user is located; a second light guiding device that guides the light projected from the second projection optical system to a second area where a second eye of the user is located; Furthermore, the first light-guiding device and the second light-guiding device guide light in a polarization state of incident light; The display device according to claim 1 .

8. the first projection optical system is disposed a first distance away from an exit surface of the polarizing beam splitter from which the first light is emitted, the second projection optical system is disposed a second distance away from the exit surface of the polarizing beam splitter for the second light, The second distance is smaller than the first distance. The display device according to claim 3 .

9. The illumination optical system includes: a first lens element disposed on an optical path of the first light emitted from the polarizing beam splitter and configured to condense the first light; a second lens element disposed on an optical path of the second light emitted from the polarizing beam splitter and configured to condense the second light; Furthermore, The refractive power of the first lens element is greater than the refractive power of the second lens element. The display device according to claim 3 .

10. a lens array element that divides the light emitted from the light source into a plurality of secondary light source lights; a lens element that condenses the plurality of secondary light source lights from the lens array element; Further provided with The display device according to claim 1 .

11. the lens array element is disposed between the light source and the polarizing beam splitter. The display device according to claim 10.

12. The lens element comprises: a first lens element disposed on an optical path of the first light emitted from the polarizing beam splitter and configured to condense the first light; a second lens element disposed on an optical path of the second light emitted from the polarizing beam splitter and configured to condense the second light; Including, The display device according to claim 10.

13. the lens array element includes a first lens array element disposed between the polarizing beam splitter and the first lens element; a second lens array element disposed between the polarizing beam splitter and the second lens element; Including, The display device according to claim 12.

14. The reflecting surface is configured by a curved surface. The display device according to claim 3 .

15. The light source includes a light source element that generates the source light; a collimator element that collimates the source light generated by the light source element; Including, The display device according to claim 1 .

16. the first projection optical system projects an image for a first eye of a user, and the second projection optical system projects an image for a second eye of the user; It is a head-mounted display The display device according to claim 1 .

17. an optical system that guides light to a first display unit of the first projection optical system and a second display unit of the second projection optical system, a light source that collimates and emits light source light including first polarized light and second polarized light; a polarizing beam splitter including a splitting surface that splits the light source light into a first light having a first polarization state and a second light having a second polarization state; Equipped with an optical system that guides the first light to the first display unit and guides the second light to the second display unit;