JP2018205418A - Display device - Google Patents

Abstract

To provide a display device that can prevent a reduction in visibility of environmental light due to reflected light.SOLUTION: A display device comprises: an image forming device; a light guide body that has a first surface and a second surface opposite to each other and guides image light generated by the image forming device; an incident unit that makes the image light incident on the light guide body; and an emission unit that is provided on the second surface of the light guide body and makes the image light emit from the light guide body. The emission unit has an optical element formed by arranging a plurality of half mirrors that are provided to be parallel to each other at a distance, reflect part of the image light and environmental light, and transmit the other part of the image light and environmental light; in the plurality of half mirrors, the reflectance of P-polarized light is higher than the reflectance of S-polarized light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a display device.

  2. Description of the Related Art In recent years, as one of wearable information devices, an image display device using a method such as a head mounted display that is worn on an observer's head has been provided. There is also known an image display device that can simultaneously view both an image generated by a display element and an image of the outside of the viewer when the viewer wears the image display device, so-called see-through type image display device. (For example, refer to Patent Document 1 below).

JP 2012-8356 A

  Incidentally, the head-mounted image display device as described above may be used outdoors. However, when the image display device is used outdoors, there is a problem that visibility of see-through light (external light) is reduced by causing glare by reflected light that is irregularly reflected by a water surface or a snow surface, for example.

  This invention is made | formed in view of such a situation, Comprising: It aims at providing the display apparatus which can suppress the fall of the visibility of the external light by reflected light.

  According to an aspect of the present invention, the image forming apparatus, a light guide body that has a first surface and a second surface facing each other, and guides image light generated by the image forming apparatus, and the image light Is incident on the light guide, and an emission unit is provided on the second surface of the light guide and emits the image light from the light guide. An optical element formed by arranging a plurality of half mirrors arranged so as to be parallel to each other and reflecting a part of the image light and the external light and transmitting the other part of the image light and the external light The plurality of half mirrors provide a display device in which the reflectance of P-polarized light is higher than the reflectance of S-polarized light.

  The display device according to the first aspect includes a plurality of half mirrors in which the reflectance of the P-polarized light is higher than the reflectance of the S-polarized light, thereby suppressing the decrease in the intensity of the image light incident on the observer's eyes, The intensity of harmful light can be reduced. Therefore, when used outdoors without using polarized sunglasses, glare generated in external light can be reduced. Therefore, it is possible to provide a display device in which the visibility of image light is secured and the deterioration of the visibility of external light due to reflected light is suppressed.

  In the above aspect, the plurality of half mirrors are preferably arranged along a horizontal direction.

  According to this configuration, since the reflection surface of the half mirror is provided along the vertical direction, light that vibrates in the horizontal direction that causes harmful light enters the half mirror as P-polarized light. Therefore, since the P-polarized light that becomes harmful light is favorably reflected by the half mirror, the above-described configuration for reducing the intensity of harmful light can be realized.

  The said aspect WHEREIN: It is preferable to further provide the polarizing plate provided in the said 1st surface side of the said light guide.

  According to this configuration, by arranging the polarizing plate on the first surface side of the light guide, it is possible to guide bright external light EL to the observer's eye EY while reducing the occurrence of ghost.

  In the above aspect, the polarizing plate is preferably detachable from the light guide.

  According to this configuration, by attaching the polarizing plate, it is possible to easily add a function of reducing ghost generation according to the application. Therefore, the versatility of the display device can be improved.

  In the above aspect, the image forming apparatus includes a light source that emits the image light composed of linearly polarized light, and a light beam expanding element that expands a light beam diameter of the image light emitted from the light source. The element is composed of a diffractive element including a grating pattern composed of a plurality of convex portions extending along the horizontal direction, and the image light is the light that vibrates along the extending direction of the plurality of convex portions. It is preferable to enter the light beam expanding element.

  According to this configuration, in the case where the light beam expanding element is used as the image forming apparatus, the polarization direction of the image light incident on the diffraction element is optimized. Therefore, the light beam diameter of the image light can be enlarged by the diffraction element. Further, since the image light whose light beam diameter has been expanded by the light beam diameter expanding element is incident on the half mirror as P-polarized light, the image light is efficiently reflected by the half mirror and is thus well guided to the eyes of the observer. Therefore, the observer can visually recognize a bright image.

The figure which shows schematic structure of the display apparatus of 1st Embodiment. The back view of a light guide device. The figure which shows the optical path of the image light in a light guide device. The figure which shows the structure of an optical element. The figure which shows the optical characteristic of a half mirror. The figure which shows the structure of the optical element which concerns on a comparative example. The figure which shows the principal part structure of the display apparatus of 2nd Embodiment. The figure which shows schematic structure of the display apparatus of 3rd Embodiment. Sectional drawing which shows typically the structure of a light beam diameter expansion element. Explanatory drawing which shows the relationship between the polarization direction of the light in a beam diameter expansion element, and a diffraction function.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the display device of this embodiment. FIG. 2 is a rear view of the light guide device. FIG. 3 is a diagram illustrating an optical path of image light in the light guide device. 1 corresponds to the AA cross section of the light guide device shown in FIG. The display device of this embodiment is used as a head mounted display, for example.

  Hereinafter, an XYZ coordinate system is used in the drawings. The X direction corresponds to the front-rear direction of the observer wearing the display device, the Y direction corresponds to the left-right direction of the observer, the Z direction is a direction orthogonal to the X direction and the Y direction, and the vertical direction of the observer Equivalent to. In the present embodiment, the -Y direction is referred to as the left direction (left side), the + Y direction as the right direction (right side), the + X direction as the front direction (front or front side), and the -X direction as the rear direction (rear side or rear side). There is also.

(Overall configuration of light guide device and display device)
As shown in FIG. 1, the display device 100 includes an image forming device 10 and a light guide device 20. The display device 100 allows an observer to visually recognize a display image as a virtual image and allows the observer to observe an outside world image with see-through. In the display device 100, the image forming device 10 and the light guide device 20 are provided in pairs corresponding to the right eye and the left eye of the observer. However, since the device for the right eye and the device for the left eye are symmetric, only the device for the left eye is shown here, and the illustration for the device for the right eye is omitted. Note that the display device 100 includes a vine portion (not shown) that an observer puts on his / her ear, and has an appearance like general glasses as a whole.

  The image forming apparatus 10 includes a liquid crystal panel 11, a projection lens 12, and a light source 14. The liquid crystal panel 11 spatially modulates illumination light from the light source 14 to form a moving image or other image light GL to be displayed. The projection lens 12 is a collimating lens that makes the image light GL emitted from each point on the liquid crystal panel 11 substantially parallel. The projection lens 12 is made of glass or plastic, and is not limited to one, but may be composed of a plurality of lenses. The projection lens 12 is not limited to a spherical lens, and may be an aspheric lens, a free-form surface lens, or the like.

  The light guide device 20 is made of a flat light transmitting member. The light guide device 20 emits the image light GL formed by the image forming device 10 as virtual image light toward the observer's eye EY, and transmits and transmits the external light (see-through light) EL constituting the external image. To the person's eyes EY. The light guide device 20 includes an incident unit 21 that takes in the image light GL, a light guide 22 that mainly guides the image light GL, and an emission unit 23 that extracts the image light GL and the external light EL. The light guide 22 and the incident portion 21 are integrally formed of a resin material having high light transmittance. In the case of this embodiment, the optical path of the image light GL propagating through the light guide device 20 is composed of one type of optical path that is reflected the same number of times, and a plurality of types of optical paths are not synthesized.

  The light guide 22 is disposed to be inclined with respect to the optical axis AX with the observer's eye EY as a reference. The normal direction T of the first surface 22a of the light guide 22 is inclined by an angle κ with respect to the optical axis AX. Thereby, the light guide 22 can be arrange | positioned along the front surface of a face, and the normal line of the 1st surface 22a of the light guide 22 has inclination with respect to the optical axis AX. As described above, when the normal line of the first surface 22a of the light guide 22 is inclined by the angle κ with respect to the z direction parallel to the optical axis AX, the optical axis AX emitted from the optical element 30 described later and the vicinity thereof are emitted. The image light GL0 forms an angle κ with respect to the normal line of the light exit surface OS.

  The incident unit 21 includes a light incident surface IS that captures the image light GL from the image forming apparatus 10 into the incident unit 21, a reflection surface RS that reflects the captured image light GL and guides the image light GL into the light guide 22. Have The light incident surface IS is formed from a concave curved surface 21b on the projection lens 12 side. The curved surface 21b also has a function of totally reflecting the image light GL reflected by the reflecting surface RS on the inner surface side.

  The reflecting surface RS is formed from a concave curved surface 21a on the projection lens 12 side. The reflective surface RS is composed of a metal film such as an aluminum film formed on the curved surface 21a by vapor deposition or the like. The reflecting surface RS reflects the image light GL incident from the light incident surface IS and bends the optical path.

  The curved surface 21b bends the optical path by totally reflecting the image light GL reflected by the reflecting surface RS inside. Thus, the incident part 21 reliably guides the image light GL into the light guide 22 by reflecting the image light GL incident from the light incident surface IS twice and bending the optical path.

  The light guide 22 is a flat light guide member that is parallel to the Z axis and inclined with respect to the Y axis, and is also referred to as a light guide. The parallel light guide (light guide) 22 is formed of a light transmissive resin material or the like. The light guide 22 has a pair of first surface 22a and second surface 22b that are substantially parallel to each other. Since the first surface 22a and the second surface 22b are parallel planes, the expansion of the external image and the focus shift do not occur. The first surface 22a functions as a total reflection surface that totally reflects the image light from the incident portion 21, and guides the image light GL to the emission portion 23 with a small loss. The first surface 22a is disposed on the outside side of the light guide 22 and functions as a first total reflection surface, and is also referred to as an outside side surface in this specification.

  The second surface 22 b located on the observer side extends to one end of the emitting unit 23. Here, the second surface 22b is a boundary surface IF between the light guide 22 and the emitting portion 23 (see FIG. 3).

  In the light guide 22, the image light GL reflected by the reflecting surface RS or the light incident surface IS of the incident portion 21 is incident on the first surface 22 a which is a total reflection surface, is totally reflected by the first surface 22 a, and is guided. The light is guided to the back side of the optical device 20, that is, the + Y side where the emission unit 23 is provided. As shown in FIG. 2, the light guide 22 has a termination surface ES as an end surface on the + Y side in the outer shape of the light guide device 20. The light guide 22 has an upper end surface TP and a lower end surface BP as end surfaces on the ± Z side.

  As shown in FIG. 3, the emitting portion 23 is configured in a plate shape along the second surface 22 b or the boundary surface IF on the back side (+ Y side) of the light guide 22. The emission unit 23 reflects the incident image light GL at a predetermined angle when passing the image light GL totally reflected by the region FR of the external surface side plane (total reflection surface) 22a of the light guide 22. Bend to the light exit surface OS side. Here, the image light GL that first enters the emission unit 23 without passing through it is an extraction target as virtual image light. That is, even if there is light reflected by the inner surface of the light emission surface OS in the emission unit 23, this is not used as image light.

  The emission unit 23 includes an optical element 30 in which a plurality of half mirrors 31 having light transmission properties and light reflection properties are arranged. The structure of the optical element 30 will be described later. The optical element 30 is provided along the second surface 22 b on the viewer side of the light guide 22. Thus, the emission part 23 is provided on the surface of the light guide 22 on the viewing side.

  Since the light guide device 20 has the above-described structure, the image light GL emitted from the image forming device 10 and incident on the light guide device 20 from the light incident surface IS is bent by a plurality of reflections at the incident portion 21 to be guided. The light is totally reflected in the region FR of the first surface 22a of the body 22 and travels substantially along the optical axis AX. The image light GL reflected by the region FR of the first surface 22 a on the + X side is incident on the emission unit 23.

  At this time, the width in the longitudinal direction of the region FR is narrower than the width in the longitudinal direction of the injection portion 23 in the YZ plane. In other words, the incident width at which the light bundle of the image light GL enters the emission unit 23 (or the optical element 30) is wider than the incident width at which the light bundle of the image light GL enters the region FR. Thus, by making the incident width of the light beam of the image light GL incident on the region FR relatively narrow, the interference of the optical path is less likely to occur, and the boundary surface IF is not used for light guiding, that is, the boundary It becomes easy to make the image light GL from the region FR directly incident on the emission part 23 (or the optical element 30) without reflecting the image light GL on the surface IF.

  The image light GL incident on the emission part 23 is in a state where it can be taken out by being bent at an appropriate angle in the emission part 23 and finally emitted from the light emission surface OS. The image light GL emitted from the light exit surface OS enters the observer's eye EY as virtual image light. By forming the virtual image light on the retina of the observer, the observer can recognize the virtual image by the image light GL.

  Here, the angle at which the image light GL used for image formation is incident on the emitting portion 23 increases as the distance from the incident portion 21 on the light source side increases. That is, image light GL having a large inclination with respect to the X direction parallel to the first surface 22a on the outside or the optical axis AX is incident on the back side of the emission unit 23 and is bent at a relatively large angle. Image light GL having a small inclination with respect to the X direction or the optical axis AX is incident on the front side of the portion 23 and is bent at a relatively small angle.

(Light path of image light)
Hereinafter, the optical path of the image light GL will be described in detail.
As shown in FIG. 3, among the image lights emitted from the emission surface 11a of the liquid crystal panel 11, the component emitted from the central portion of the emission surface 11a indicated by the broken line is defined as the image light GL0 and indicated by a one-dot chain line. The component emitted from the left side (−Y and + X side) of the drawing surface 11a in the periphery of the emission surface 11a is the image light GL1, and the right side (+ Y and −X side) of the drawing surface 11a indicated by the two-dot chain line. Let the component emitted from the image light GL2. Of these, the optical path of the image light GL0 is assumed to extend along the optical axis AX.

  The image lights GL0, GL1, and GL2 that have passed through the projection lens 12 are respectively incident from the light incident surface IS of the light guide device 20, and then pass through the light guide 22 through the incident portion 21 to reach the emission portion 23. Specifically, among the image lights GL0, GL1, and GL2, the image light GL0 emitted from the central portion of the emission surface 11a is bent at the incident portion 21 and coupled into the light guide 22 and then the standard reflection. The light enters the region FR of the first surface 22a at the angle θ0 and is totally reflected, and passes through the boundary surface IF without being reflected by the boundary surface IF between the light guide 22 and the emitting portion 23 (or the optical element 30). Then, the light directly enters the central portion 23k of the emitting portion 23. The image light GL0 is reflected at a predetermined angle at the portion 23k, and is parallel to the optical axis AX direction (direction of angle κ with respect to the X direction) inclined from the light exit surface OS to the YZ plane including the light exit surface OS. It is emitted as a light beam.

  The image light GL1 emitted from one end side (−Y side) of the emission surface 11a is bent at the incident portion 21 and coupled into the light guide 22, and then the region FR of the first surface 22a at the maximum reflection angle θ1. And is totally reflected, passes through the boundary surface IF without being reflected by the boundary surface IF between the light guide 22 and the emission portion 23 (or the optical element 30), and the back side (+ Y side) of the emission portion 23 ) At a predetermined angle and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. At this time, the exit angle γ1 is relatively large in the angle returned to the incident portion 21 side.

  On the other hand, the image light GL2 emitted from the other end side (+ Y side) of the emission surface 11a is bent by the incident portion 21 and coupled into the light guide 22, and then the minimum reflection angle θ2 of the first surface 22a. The light enters the region FR, is totally reflected, passes through the boundary surface IF without being reflected by the boundary surface IF between the light guide 22 and the emission unit 23 (or the optical element 30), and enters the entrance side ( -Y side) portion 23m is reflected at a predetermined angle, and is emitted as a parallel light flux from the light exit surface OS toward the predetermined angle direction. In this case, the exit angle γ2 is relatively small in the angle returned to the incident portion 21 side.

  Note that the image light GL0, GL1, and GL2 have been described as representative of a part of the entire light beam of the image light GL, but the light beam components constituting the other image light GL are also similar to the image light GL0 and the like. It is guided and emitted from the light exit surface OS. Therefore, illustration and description of these are omitted.

  Here, as an example of the value of the refractive index n of the transparent resin material used for the incident portion 21 and the light guide 22, assuming that n = 1.4, the value of the critical angle θc is θc≈45.6 °. Of the reflection angles θ0, θ1, and θ2 of the image lights GL0, GL1, and GL2, the minimum reflection angle θ2 is set to a value larger than the critical angle θc, thereby satisfying the total reflection condition for the necessary image light. be able to.

  The image light GL0 directed toward the center is incident on the portion 23k of the emission unit 23 at an elevation angle φ0 (= 90 ° −θ0). The image light GL1 for the periphery is incident on the portion 23h of the emission unit 23 at an elevation angle φ1 (= 90 ° −θ1). The image light GL2 for the periphery enters the portion 23m of the emission unit 23 at an elevation angle φ2 (= 90 ° −θ2). Here, the relationship of φ2> φ0> φ1 is established between the elevation angles φ0, φ1, and φ2, reflecting the magnitude relationship of the reflection angles θ0, θ1, and θ2. That is, the incident angle of the optical element 30 to the half mirror 31 gradually decreases in the order of the portion 23m corresponding to the elevation angle φ2, the portion 23k corresponding to the elevation angle φ0, and the portion 23h corresponding to the elevation angle φ1. In other words, the incident angle to the half mirror 31 or the reflection angle at the half mirror 31 decreases as the distance from the incident portion 21 increases.

(Configuration of optical element)
Next, the configuration of the optical element 30 will be described. FIG. 4 is a diagram showing the configuration of the optical element 30. As shown in FIG. 4, the optical element 30 includes a plurality of half mirrors 31 and a plurality of translucent members 32. The optical element 30 has a configuration in which a plurality of translucent members 32 sandwich a half mirror 31 between two adjacent translucent members 32. In other words, the optical element 30 has a configuration in which the half mirrors 31 and the translucent members 32 are alternately arranged.

  As shown in FIG. 4, the translucent member 32 is a columnar member whose cross-sectional shape perpendicular to the longitudinal direction (Z direction) is a parallelogram. Therefore, the translucent member 32 has two sets of a pair of planes extending in parallel to the longitudinal direction and parallel to each other. Of these two pairs of planes, one plane of one set is an incident surface 32a on which the image light GL and the external light EL are incident, and the other plane of one set is the image light GL and the external light EL. It is the injection surface 32b to inject. A half mirror 31 is provided on one plane of the other set. The translucent member 32 is made of, for example, glass or transparent resin.

  The plurality of translucent members 32 are all configured to have the same shape and the same dimensions. Therefore, when a plurality of pairs of a pair of translucent members 32 and half mirrors 31 are bonded together, the plurality of half mirrors 31 are arranged in parallel with each other at an equal pitch. Although not shown in FIG. 4, an adhesive layer is provided between one surface of the half mirror 31 and the adjacent translucent member 32. Thereby, the optical element 30 becomes a rectangular plate-like member as a whole. When the optical element 30 is viewed from the normal direction of the incident surface 32a or the exit surface 32b of the translucent member 32, a plurality of thin strip-shaped half mirrors 31 are arranged in a stripe shape. That is, the optical element 30 has a configuration in which a plurality of rectangular half mirrors 31 are arranged at a predetermined interval (pitch PT) in the extending direction (long side direction) of the light guide 22. That is, the plurality of half mirrors 31 are arranged along the horizontal direction (direction parallel to the XY plane). Specifically, the plurality of half mirrors 31 are arranged along a direction inclined by an angle κ with respect to the Y direction.

  The adjacent half mirrors 31 do not have to be completely parallel to each other. For example, when light of the same angle is incident on a plurality of half mirrors 31, the plurality of half mirrors 31 are only required if the angle difference between the lights reflected from the half mirrors 31 is not visible to the observer. It can be considered that they are parallel to each other. As an example, when the visual acuity of the observer is 1.0, the observer has a resolution of 1/60 degrees, so that the angle difference between the lights reflected from the respective half mirrors 31 is half of that. If the angle is 1 / 120th of an angle, the observer cannot visually recognize the difference, and the plurality of half mirrors 31 can be regarded as being parallel to each other. As another example, if the angle difference between the lights reflected from the respective half mirrors 31 is an angle difference equal to or less than half of the pixels of the image forming apparatus 10, the observer cannot visually recognize the difference. It can be considered that the plurality of half mirrors 31 are parallel to each other. For example, when the left and right angle of view of the image light GL is 30 degrees and the number of left and right pixels is 1280 pixels, the angle of the half pixel is 30 ÷ 1280 ÷ 2 = 0.012, so the half angle Can be regarded as being parallel to each other.

  The half mirror 31 is provided such that the short side of the half mirror 31 is inclined with respect to the entrance surface 32a and the exit surface 32b of the translucent member. More specifically, the half mirror 31 is inclined so that the reflection surface 31r faces the incident portion 21 side toward the outside of the light guide 22. In other words, the half mirror 31 is configured so that the upper end (+ X side) rotates counterclockwise with the long side (Z direction) of the half mirror 31 as an axis and the XZ plane orthogonal to the first surfaces 22a and 22b as a reference. Inclined.

  Hereinafter, the angle formed by the reflection surface 31r of the half mirror 31 and the emission surface 32b of the translucent member 32 is defined as the inclination angle δ of the half mirror 31. In the present embodiment, the inclination angle δ of the half mirror 31 is 45 ° or more and less than 90 °. In this embodiment, although the refractive index of the translucent member 32 and the refractive index of the light guide 22 are equal, these refractive indexes may differ. When the refractive indexes are different, it is necessary to change the inclination angle δ of the half mirror 31 with respect to the case where the refractive indexes are equal.

In the present embodiment, the half mirror 31 is formed of, for example, a dielectric multilayer film or a metal film sandwiched between the translucent members 32. The plurality of half mirrors 31 are configured by stacking, for example, TiO ₂ : 39 nm, Ag: 18 nm, and TiO ₂ : 37 nm. Therefore, each of the plurality of half mirrors 31 has the same characteristics.

  FIG. 5 is a diagram showing the optical characteristics of the half mirror 31. The horizontal axis in FIG. 5 is the wavelength of light incident on the half mirror 31 (unit: nm), the left vertical axis is the reflectance (unit:%), and the right vertical axis is the transmittance (unit:%). .

In FIG. 5, R _p is the reflectance of P-polarized light, T _p is the transmittance of P-polarized light, R _s is the reflectance of S-polarized light, and T _s is the transmittance of S-polarized light. As shown in FIG. 5, the optical characteristics of the half mirror 31, although somewhat varying depending on the wavelength band, at any wavelength range, reflectance R _P of the P-polarized light is higher than the reflectance R _s of the S-polarized light Yes.

  Here, functions of the plurality of half mirrors 31 constituting the optical element 30 will be described. In the following, for simplicity of explanation, the external light EL enters the optical element 30 from the direction perpendicular to the X axis (the optical axis AX direction), travels straight, and exits from the exit surface 32b in the X axis direction. (See FIG. 4).

  As shown in FIG. 4, the image light GL is incident on the optical element 30 at an elevation angle φ and is emitted from the optical element 30 in the X-axis direction. It is assumed that the image light GL is incident on the reflecting surface 31r of the half mirror 31 as P-polarized light.

External light EL includes S-polarized light _{L S} and P-polarized light _{L P} for the half mirror 31.

In FIG. 4, the S-polarized light L _S after passing through the half mirror 31 is denoted by a symbol L _S-T, and the P-polarized light Lp after passing through the half mirror 31 is denoted by a symbol L _P-T. The S-polarized light L _S after being reflected once by two mirrors and reflected twice is denoted as L _S-RR, and is reflected once by two adjacent mirrors in the half mirror 31 to be reflected twice. The P-polarized light L _P after this is designated as L _P-RR .

Hereinafter, in order to simplify the description, the case where the optical characteristics of the half mirror 31 are set to, for example, Rs: 0, Rp: 0.4, Ts: 0.9, and Tp: 0.5 will be described as an example. Also, a case in which set the original intensity of the S-polarized light L _S and P-polarized light L _P (intensity before incidence on the display device 100) to 1.0 as an example. In this case, as shown in FIG. 4, the intensity of each polarized light occupying the external light EL that passes through the half mirror 31 and enters the eye EY of the observer is P-polarized light L _P−T : 0.5, P-polarized light L _P-RR: 0.16, S-polarized light _L S-T: 0.9, S-polarized light _{L S-RR:} zero.

  By the way, the ambient light EL may include reflected light that is irregularly reflected on an object surface such as a water surface or a snow surface. Such reflected light includes a lot of light that vibrates in the left-right direction with respect to the eye EY of the observer, and is light that causes discomfort to the observer by causing glare in the external light EL. That is, the external light EL includes harmful light for the observer.

  Conventionally, polarized sunglasses have been used as means for preventing harmful light contained in the external light EL. Polarized sunglasses cuts polarized light that vibrates in the left-right direction with respect to the eye EY of the observer (the above-described polarization component that becomes harmful light), and transmits only polarized light that vibrates in the vertical direction with respect to the eye EY of the observer. .

  In the present embodiment, as shown in FIG. 4, the plurality of half mirrors 31 are arranged along the horizontal direction (a direction parallel to the XY plane and inclined by an angle κ in the X direction). That is, the reflecting surface 31r of the half mirror 31 is provided in parallel with the vertical direction (Z direction) of the observer. Therefore, the light that vibrates in the left-right direction (Y direction) with respect to the eye EY of the observer becomes P-polarized light with respect to the reflection surface 31 r of the half mirror 31.

In the following, it is assumed that all the P-polarized light with respect to the half mirror 31 out of the external light EL incident on the observer's eye EY through the optical element 30 is harmful light. In the emission unit 23 of the present embodiment, P-polarized light L _P-T and P-polarized light L _P-RR among the light incident on the eyes EY of the observer correspond to harmful light. Therefore, when the optical element 30 (half mirror 31) of the present embodiment is used, the intensity of harmful light entering the observer's eye EY is 0.66.

  Here, as an optical element of the comparative example, an element using a half mirror 31A in which the reflectance of P-polarized light is lower than the reflectance of S-polarized light instead of the half mirror 31 will be considered. FIG. 6 is a diagram showing a configuration of an optical element 30A of a comparative example. The configuration of the optical element 30A of the comparative example is the same as that of the optical element 30 of the present embodiment except for the half mirror 31A.

As shown in FIG. 6, in the optical element 30A of the comparative example, for example, the optical characteristics of the half mirror are Rs: 0.4, Rp: 0, Ts: 0.6, and Tp: 1.0. Further, the original intensity of the S-polarized light L _S and the P-polarized light L _P is set to 1.0.

When the optical element 30A of the comparative example is used, the intensity of each polarized light occupying the external light EL that is transmitted through the half mirror 31A and incident on the observer's eye EY is P-polarized light L _P−T : 1.0, P-polarized light L _P-RR : 0, S-polarized light L _S-T : 0.6, S-polarized light L _S-RR : 0.16.

Also in the optical element 30A of the comparative example, the P-polarized light L _P-T and the P-polarized light L _{P-RR of} the light incident on the observer's eye EY correspond to harmful light. That is, when the optical element 30A of the comparative example is used, the intensity of harmful light incident on the observer's eye EY is 1.0.

Next, the intensity of the image light GL incident on the observer's eye EY will be described. Image light GL includes S polarized light _{G S} and P-polarized _{G P} for the half mirror 31.

As shown in FIG. 4, in the image light GL, the S-polarized light G _S after being reflected by the half mirror 31 is denoted as G _S-R, and after being transmitted through the half mirror 31 and further reflected by another half mirror 31. After the S-polarized light G _S is denoted by G _S-TR and the P-polarized light GP reflected by the half mirror 31 is _denoted by G _GP-R , after being transmitted through the half mirror 31 and further reflected by another half mirror 31 The P-polarized light _GP is designated as _GP-TR .

Here, a case where the original intensity of the image light GL (intensity before entering the optical element 30) is set to 1.0 will be described. Since the image light GL is incident on the half mirror 31 as P-polarized light, the image light GL is not necessary to consider the S-polarized component, the intensity of the S-polarized G _S described above is zero.

Therefore, the intensity of the image light GL guided to the observer's eye EY by the emitting unit 23 after being guided through the light guide 22 is P-polarized light G _P-R : 0.4, P-polarized light G _P-TR : 0. .2, S-polarized light G _S-R : 0, S-polarized light G _S-TR : 0. That is, the intensity of the image light GL incident on the observer's eye EY via the optical element 30 (half mirror 31) of the present embodiment is 0.6.

On the other hand, as shown in FIG. 6, when the optical element 30 </ b> A of the comparative example is used, the intensity of the image light GL guided to the observer's eye EY is P-polarized G _P-R : 0, P-polarized G _P-TR : 0, S-polarized _G S-T: 0.4, S-polarized _G S-TR: 0.24. That is, when the optical element 30A of the comparative example is used, the intensity of the image light GL incident on the observer's eye EY is 0.64.

As described above, according to the optical element 30 of the present embodiment, the optical element 30A of the comparative example is provided by including the plurality of half mirrors 31 in which the reflectance RP of _P- polarized light is higher than the reflectance R _s of S-polarized light. On the other hand, the intensity of harmful light can be reduced while suppressing a decrease in the intensity of the image light GL incident on the eye EY of the observer.

  Therefore, according to the display device 100 of the present embodiment, it is possible to reduce glare that occurs in the external light EL when used outdoors without using polarized sunglasses. Therefore, it is possible to suppress a decrease in the visibility of the external light due to the reflected light while ensuring the visibility of the image light GL.

(Second Embodiment)
Subsequently, a display device according to the second embodiment will be described. In addition, about the structure which is common in 1st Embodiment, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

  FIG. 7 is a diagram illustrating a main configuration of the display device 200 according to the second embodiment, and specifically illustrates a peripheral configuration of the emission unit 123 of the light guide 22. As shown in FIG. 7, the display device 200 of this embodiment includes a polarizing plate 40 provided on the first surface 22 a side of the light guide 22.

  The polarizing plate 40 may be provided so as to be in contact with the first surface 22a of the light guide 22 or may be provided at a position separated from the first surface 22a. In the present embodiment, the polarizing plate 40 is disposed at a position slightly away from the first surface 22a. The polarizing plate 40 can be attached to and detached from a main body (not shown) in the display device 200. The display device 200 with the polarizing plate 40 removed has the same visibility as the display device 100 of the first embodiment.

  As the polarizing plate 40 of this embodiment, the thing similar to the lens of polarized sunglasses was used. The polarizing plate 40 is provided on the first surface 22a side of the light guide 22 so as to cut polarized light that vibrates in the left-right direction with respect to the eye EY of the observer.

  Also in this embodiment, as shown in FIG. 7, it is assumed that the external light EL enters the optical element 30 from the vertical direction (optical axis AX direction) and travels straight, and exits from the exit surface 32b in the vertical direction.

  In the present embodiment, the external light EL passes through the polarizing plate 40 and enters the optical element 30. The external light EL1 transmitted through the polarizing plate 40 becomes polarized light that vibrates in the vertical direction (Z direction) with respect to the observer's eye EY.

  Since the reflection surface 31r of the half mirror 31 is provided along the observer's vertical direction (Z direction), the external light EL1 that vibrates in the vertical direction with respect to the eye EY of the observer is the reflection surface 31r of the half mirror 31. Corresponds to S-polarized light.

In the present embodiment, the external light EL1 incident on the half mirror 31 is composed only of S-polarized light L _S. Therefore, only the S-polarized light L _S is considered as the external light EL.

In this embodiment, the optical characteristics of the half mirror 31, Rs: 0, Rp: 0.4, Ts: 0.9, Tp: 0.5 and set, the original intensity of S-polarized light _{L S} 1. Take the case of 0 as an example. In this case, as shown in FIG. 7, the intensity of each polarization occupying the external light EL1 incident on the observer's eye EY transmitted through the half mirror 31, S-polarized light L _S-T: 0.9, _S-polarized light L _S-RR : 0.

By the way, the external light EL from the close object seen through the optical element 30 has a divergence angle. Therefore, in a state where the focus of the observer's eye EY is adjusted to a close object, the S-polarized light L _S-T incident on the eye EY at the same angle via two half mirrors 31A and 31B that are different in position and extend in parallel. And S-polarized light L _S-RR coexist, causing a ghost in which images are slightly shifted and superimposed.

On the other hand, according to the display device 200 of the present embodiment, since the intensity of the _S- polarized light L _S-RR becomes 0, the external light EL incident on the observer's eye EY is composed only of the _S- polarized light L _S-T. Will be. Therefore, it is possible to suppress the ghost from being observed when a close object viewed through the optical element 30 is viewed.

Here, the case where the optical element 30A of the comparative example using the half mirror 31A in which the reflectance of the P-polarized light is lower than the reflectance of the S-polarized light is also examined. As for the optical element 30A of the comparative example, similarly to the first embodiment, the optical characteristics of the half mirror are Rs: 0.4, Rp: 0, Ts: 0.6, Tp: 1.0, S-polarized light. The original intensity of L _S and P polarization L _P was set to 1.0.

When using the optical element 30A of the comparative example, the intensity of each polarization occupying the external light EL that is incident on the observer's eye EY transmitted through the half mirror 31A is, S-polarized light L _S-T: 0.6, _S-polarized light L _S-RR : 0.16 (see FIG. 6).

In the configuration using the optical element 30A of the comparative example, even when the polarizing plate 40 is provided on the first surface 22a of the light guide 22, the intensity of the _S- polarized light L _S-RR does not become zero. That is, as the external light EL, light in which _S- polarized light L _S-T and S-polarized light L _S-RR coexist enters the eye EY of the observer. Therefore, when a close object viewed through the optical element 30A of the comparative example is viewed, a ghost in which the images are slightly shifted and superimposed is generated.

  As described above, according to the display device 200 of the present embodiment, by arranging the polarizing plate 40 on the first surface 22a of the light guide 22, the ghost occurrence is reduced and bright compared to the configuration of the comparative example. The ambient light EL can be guided to the observer's eye EY.

  That is, according to the display device 200 of the present embodiment, the combination of the optical element 30 and the polarizing plate 40 has a remarkable effect of reducing the generation of ghosts that could not be achieved even when a conventional polarizing lens was used. Can be obtained.

  In addition, since the polarizing plate 40 is detachable, a function for reducing ghost generation can be easily added by attaching the polarizing plate 40 according to the application. On the other hand, by removing the polarizing plate 40, the display device 100 according to the first embodiment can be used only for reducing harmful light. Therefore, the versatility of the display device 200 can be improved.

  In the present embodiment, the image light GL is not affected by the presence or absence of the polarizing plate 40. Therefore, the intensity of the image light GL incident on the observer's eye EY is the same as that in the first embodiment, and thus the description thereof is omitted.

  Since the image light GL can be regarded as light from infinity, the ghost as described above is not a concern with the image light GL. Therefore, when designing the half mirror 31, it is not necessary to preferentially consider the occurrence of ghost for the image light GL.

(Third embodiment)
Subsequently, a display device according to a third embodiment will be described. The difference between the present embodiment and the first embodiment is the configuration of the image forming apparatus, and the other configurations are the same. For this reason, the same reference numerals are assigned to configurations common to the first embodiment, and detailed description thereof is omitted.

  The display device of this embodiment is a see-through retinal scanning display device. FIG. 8 is a diagram showing a schematic configuration of a see-through type retinal scanning display device 300.

  As shown in FIG. 8, the display device 300 of this embodiment includes an image forming device 110 and a light guide device 120. The light guide device 120 has the same configuration as the light guide device 20 of the first embodiment.

  The image forming apparatus 110 includes a light source unit 111 that emits image light L1 for displaying an image, and a scanning optical system 113 that includes a scanning mirror 112 that scans the image light L1 emitted from the light source unit 111 into an image. And a light guide system 114 that makes the image light L1 scanned by the scanning optical system 113 enter the eye EY of the observer, and a light beam diameter enlarging element 115.

  In the present embodiment, the light source unit 111 includes laser elements that emit red light, blue light, and green light, respectively. The scanning optical system 113 can be realized by, for example, a micromirror device formed by MEMS technology.

  The light beam diameter enlarging element 115 is for enlarging the image light L1 emitted from the scanning optical system 113 so that the image of the observer can easily see the image. Thus, even when the position of the observer's eyes is changed by enlarging the image light L1, it is possible to visually recognize a high-quality image that does not lack a visual field.

  FIG. 9 is a cross-sectional view schematically showing the configuration of the light beam diameter expanding element 115 and a ray diagram of light passing through the light beam diameter expanding element 115. FIG. 10 is an explanatory diagram showing the relationship between the polarization direction of light and the diffraction function in the light beam diameter enlarging element 115.

  As shown in FIG. 9, the light beam diameter enlarging element 115 of this embodiment includes a translucent substrate 116, a first diffraction grating 117 provided on the first surface 116 a of the translucent substrate 116, and a translucent property. And a second diffraction grating 118 provided on the second surface 116 b of the substrate 116.

  Hereinafter, in FIGS. 8 to 10, description will be made using another X′Y′Z ′ coordinate system. The X ′ direction corresponds to the normal direction of a pair of surfaces (the first surface 116 a and the second surface 116 b) in the translucent substrate 116, the Y ′ direction corresponds to the vertical direction, the Z ′ direction corresponds to the X ′ direction, and This corresponds to the direction orthogonal to the Y ′ direction. As shown in FIG. 8, the X ′ direction and the Y ′ direction of the X′Y′Z ′ coordinate system are directions in which the X axis and the Y axis in the XYZ coordinate system are rotated clockwise around the Z axis, respectively. And the Z ′ direction of the X′Y′Z ′ coordinate system coincides with the Z direction of the XYZ coordinate system.

  The first diffraction grating 117 has a grating pattern composed of a plurality of convex portions 117a extending linearly along the Y ′ direction. The second diffraction grating 118 has a grating pattern composed of a plurality of convex portions 118a extending linearly along the Y ′ direction. The first diffraction grating 117 and the second diffraction grating 118 have the same grating period.

  Here, the diffraction efficiency of the first diffraction grating 117 and the second diffraction grating 118 differs depending on the oscillation direction of the incident polarized light. Specifically, when the image light L1 is incident on the first diffraction grating 117 and the second diffraction grating 118 as TM light that vibrates in the Z ′ direction, the beam diameter of the first diffraction grating 117 and the second diffraction grating 118 is reduced. The enlargement function (diffraction function) cannot be sufficiently obtained.

On the other hand, in the present embodiment, the image light L1 emitted from the laser element used in the light source unit 111 is incident on the light beam diameter expanding element 115 in the Y ′ direction (extension direction of the convex portions 117a and 118a). The polarized light oscillates. That is, the image light L1 emitted from the light source unit 111 is applied to the first diffraction grating 117 and the second diffraction grating 118 each having a grating pattern including convex portions 117a and 118a extending linearly in the Y ′ direction. It enters as TE light. Therefore, the image light L1 is diffracted by the first diffraction grating 117 and the second diffraction grating 118 as shown in FIG.
The configurations of the first diffraction grating 117 and the second diffraction grating 118 are not limited to the above. For example, a configuration in which a member having a different refractive index or a metal wire is embedded between the plurality of protrusions 117a and the plurality of protrusions 118a may be employed.

  According to the present embodiment, the function of expanding the light beam diameter by the light beam diameter expanding element 115 can be satisfactorily exhibited by adjusting the incident direction of the image light L1 with respect to the light beam diameter expanding element 115.

  Further, the image light L1 whose light beam diameter is expanded by the light beam diameter expanding element 115 is polarized light that vibrates along the Y ′ direction. That is, the image light L1 can also be said to be polarized light that vibrates along the XY plane in the XYZ coordinate system. Such polarized light oscillating along the XY plane corresponds to P-polarized light with respect to the reflecting surface 31 r of the half mirror 31.

In the half mirror 31 of the present embodiment, the reflectance R _P of the P-polarized light is higher than the reflectance R _s of the S-polarized light as discussed above. For this reason, the image light L1 is efficiently reflected by the half mirror 31 to be guided well to the observer's eye EY.
As described above, according to the display device of the present embodiment, high light utilization efficiency can be realized by efficiently guiding the image light L1 emitted from the image forming apparatus 110 to the eyes EY of the observer. Therefore, the observer can visually recognize a bright image.

  The image forming apparatus 110 according to the present embodiment may be applied to the display device 200 according to the second embodiment. In this way, it is possible to provide a highly reliable display device that allows the observer to visually recognize the external light EL and the bright image light L1 with reduced harmful light and ghost.

  In addition, this invention is not limited to the content of the said embodiment, In the range which does not deviate from the main point of invention, it can change suitably. In the above-described embodiment, the case where the image light GL emitted from the image forming apparatus 10 is linearly polarized is described as an example, but the present invention is not limited to this. For example, an organic EL display device may be used in place of the liquid crystal panel 11 in the image forming apparatus 10.

  Further, the display device 100 according to the first embodiment and the polarized sunglasses may be put together by an observer so that a configuration for reducing ghosts may be realized as in the display device 200 according to the second embodiment.

  In addition, although a case where a laser element is used as the light source unit 111 of the image forming apparatus 110 has been described as an example, a light source that emits randomly polarized light and polarization conversion that aligns the light emitted from the light source with polarized light that vibrates in the y direction. You may employ | adopt the thing of the structure which combined optical elements, such as an element and a polarizing plate.

  Further, in the above-described embodiment, the display devices 100 and 200 are configured such that the image forming device 10 and the light guide device 20 are provided for each of the right eye and the left eye. The image forming device 10 and the light guide device 20 may be provided for only one of them, and the image may be applied to a monocular display device, that is, a monocular display device.

  In the embodiment described above, the display device is specifically described as a head-mounted display. However, the display device of the present invention can be applied to a head-up display, a binocular-type handheld display, and the like. .

  DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus, 14 ... Light source, 21 ... Incident part, 22 ... Light guide, 22a ... 1st surface, 22b ... 2nd surface, 23 ... Ejection part, 30, 30A ... Optical element 31, 31A ... Half Mirror, 40 ... Polarizing plate, 100 ... Display device, 110 ... Image forming device, 115 ... Light beam diameter enlarging element, 123 ... Ejection part, 200, 300 ... Display device, EL, EL1 ... External light, GL0, GL1, GL2, GL, L1 ... image light, GP ... P-polarized light, GS ... S-polarized light, LP ... P-polarized light, LS ... S-polarized light.

Claims (5)

An image forming apparatus;
A light guide having a first surface and a second surface facing each other, for guiding image light generated by the image forming apparatus;
An incident portion for causing the image light to enter the light guide;
An emission unit provided on the second surface of the light guide and emitting the image light from the light guide;
A plurality of half mirrors provided so as to be parallel to each other at an interval and reflecting a part of the image light and the external light and transmitting the other part of the image light and the external light; An optical element formed by arranging
The plurality of half mirrors have a P-polarized light reflectance higher than an S-polarized light reflectance. The display device according to claim 1, wherein the plurality of half mirrors are arranged along a horizontal direction. The display device according to claim 1, further comprising a polarizing plate provided on the first surface side of the light guide. The display device according to claim 3, wherein the polarizing plate is detachable from the light guide. The image forming apparatus includes a light source that emits the image light composed of linearly polarized light, and a light flux expanding element that expands a light beam diameter of the image light emitted from the light source,
The light beam expanding element is composed of a diffractive element including a grating pattern composed of a plurality of convex portions extending along the horizontal direction,
The display device according to claim 2, wherein the image light is incident on the light beam expanding element as light that vibrates along an extending direction of the plurality of convex portions.

Images