Display device and projector

Abstract

To reduce speckle noise using polarization in a display device displaying using polarization of a laser beam.SOLUTION: A display device comprises: a laser source emitting a linearly polarized laser beam; a spatial modulator modulating spatial polarization distribution of the laser beam emitted from the laser source; and a retardation plate including a first region with birefringence and a second region without birefringence, and rotating polarization direction of a laser beam, of laser beams emitted from the spatial modulator, passing through the first region by 90 degrees.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a display device and a projector. [Background technology]

[0002] Conventionally, display devices and projectors that spatially modulate laser light are known. For example, Patent Document 1 discloses a display device such as an image projector that includes a retardation plate having birefringence in order to reduce speckle noise. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-161915 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the display device described in Patent Document 1, the entire area of ​​the retardation plate has birefringence, so that the performance of reducing speckle noise may be reduced.

[0005] An object of an embodiment of the present disclosure is to provide a display device with high speckle noise reduction performance. [Means for solving the problem]

[0006] A display device according to one embodiment of the present disclosure includes a laser light source that emits linearly polarized laser light, a spatial modulator that modulates the spatial polarization distribution of the laser light emitted from the laser light source, and a retardation plate that includes a first region having birefringence and a second region not having birefringence, and that rotates the polarization direction of the laser light that passes through the first region by 90 degrees out of the laser light emitted from the spatial modulator. Effect of the Invention

[0007] According to an embodiment of the present disclosure, a display device with high speckle noise reduction performance can be provided. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view showing a display device according to a first embodiment. [Diagram 2] 2 is a schematic cross-sectional view showing a projection lens of the display device according to the first embodiment. FIG. [Diagram 3] FIG. 2 is a schematic plan view showing a first example of a retardation plate in the display device according to the first embodiment. [Figure 4] 4 is a schematic plan view showing a retardation plate rotated from the state shown in FIG. 3. [Diagram 5] 5 is a schematic plan view showing a retardation plate rotated from the state shown in FIG. 4. [Figure 6] 4 is a schematic plan view showing a second example of a retardation plate in the display device according to the first embodiment. FIG. [Figure 7] FIG. 11 is a schematic diagram showing a display device according to a second embodiment. [Figure 8] FIG. 11 is a schematic diagram showing a display device according to a third embodiment. [Figure 9] FIG. 13 is a schematic diagram showing a head mounted display according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] A display device and a projector according to an embodiment of the present disclosure will be described in detail with reference to the drawings. However, the following embodiments are merely illustrative of a display device and a projector for embodying the technical idea of ​​the present disclosure, and are not limited thereto. Furthermore, unless otherwise specified, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments are merely illustrative examples, and are not intended to limit the scope of the present disclosure thereto. The sizes, positional relationships, and the like of the components shown in each drawing may be exaggerated to clarify the explanation. In the following explanation, the same names and symbols indicate the same or similar components, and detailed explanations will be omitted as appropriate. An end view showing only a cut surface may be used as a cross-sectional view.

[0010] In each drawing, a rectangular coordinate system having an X-axis, a Y-axis, and a Z-axis is used to express directions. The X-axis, the Y-axis, and the Z-axis are mutually orthogonal. The side toward which the arrow points in the X direction along the X-axis is indicated as the +X side, and the opposite side of the +X side is indicated as the -X side. The side toward which the arrow points in the Y direction along the Y-axis is indicated as the +Y side, and the opposite side of the +Y side is indicated as the -Y side. The side toward which the arrow points in the Z direction along the Z-axis is indicated as the +Z side, and the opposite side of the +Z side is indicated as the -Z side. However, these directional expressions do not limit the orientation of the display device and projector according to the embodiment when used, and the orientation of the display device and projector according to the embodiment when used is arbitrary.

[0011] In the following embodiments, along the X-axis, Y-axis, and Z-axis includes the object having a tilt within a range of ±10 degrees with respect to these axes. In the embodiments, each of the orthogonal and perpendicular directions may have an error within ±10 degrees with respect to 90 degrees. Furthermore, a rotation of 90 degrees may have an error within ±10 degrees. Furthermore, half of the object may have an error within ±10% of the object. Viewing an object from the normal direction is called planar view.

[0012] In addition, in this specification or claims, when there are multiple elements of a certain type and each element is to be expressed with a distinction, the elements may be distinguished by adding "first," "second," etc. to the beginning of the element. In addition, the objects to be distinguished may differ between this specification and the claims. Therefore, even if the claims describe an element with the same notation as this specification, the object identified by this element may not match between this specification and the claims.

[0013] [First embodiment] <Overall configuration example of the display device 100> Fig. 1 is a schematic cross-sectional view showing an example of a display device 100 according to a first embodiment. Fig. 1 shows a cross section of the display device 100 cut along a virtual plane (e.g., an XZ plane) including an optical axis 40 of a projection lens 4. The display device 100 is, for example, a projector.

[0014] The display device 100 includes a laser light source 1 that emits linearly polarized laser light L, a spatial modulator 2 that modulates the spatial polarization distribution of the laser light L emitted from the laser light source 1, and a retardation plate 3 that includes a first region having birefringence and a second region not having birefringence and rotates by 90 degrees the polarization direction of the laser light L that passes through the first region out of the laser light L emitted from the spatial modulator 2. In the example shown in Fig. 1, the display device 100 includes a projection lens 4 that projects the laser light L from the spatial modulator 2, and a rotation mechanism 30 that rotates the retardation plate 3 around an optical axis 40 of the projection lens 4.

[0015] In the example shown in FIG. 1, the display device 100 further includes a collimator lens 5, a first dichroic mirror 6, an integrator optical system 7, and a prism 8. The collimator lens 5 is a collimator lens.

[0016] The laser light source 1 includes a red semiconductor laser element 110, a green semiconductor laser element 120, and a blue semiconductor laser element 130. The laser light source 1 can emit red laser light Lr from the red semiconductor laser element 110, emit green laser light Lg from the green semiconductor laser element 120, and emit blue laser light Lb from the blue semiconductor laser element 130. In the example shown in Fig. 1, each of the red semiconductor laser element 110, the green semiconductor laser element 120, and the blue semiconductor laser element 130 can emit either P-polarized or S-polarized laser light.

[0017] The collimating lens 5 approximately collimates the laser light L emitted from the laser light source 1. The collimating lens 5 includes a red collimating lens 51, a green collimating lens 52, and a blue collimating lens 53. The red collimating lens 51 approximately collimates the red laser light Lr from the red semiconductor laser element 110. The green collimating lens 52 approximately collimates the green laser light Lg from the green semiconductor laser element 120. The blue collimating lens 53 approximately collimates the blue laser light Lb from the blue semiconductor laser element 130.

[0018] The first dichroic mirror 6 combines the red laser light Lr from the red collimating lens 51, the green laser light Lg from the green collimating lens 52, and the blue laser light Lb from the blue collimating lens 53. The first dichroic mirror 6 includes a first red dichroic mirror 61, a first green dichroic mirror 62, and a first blue dichroic mirror 63. The first red dichroic mirror 61 reflects the red laser light Lr from the red collimating lens 51. The first red dichroic mirror 61 may be a simple mirror that does not have wavelength selectivity. The first green dichroic mirror 62 reflects the green laser light Lg from the green collimating lens 52 and transmits the red laser light Lr from the first red dichroic mirror 61. The first blue dichroic mirror 63 transmits the blue laser light Lb from the blue collimator lens 53 and reflects the red laser light Lr from the first red dichroic mirror 61 and the green laser light Lg from the first green dichroic mirror 62.

[0019] The integrator optical system 7 transmits the laser light L combined by the first dichroic mirror 6, and makes the illuminance of the laser light L approximately uniform at the position of the spatial modulator 2. The integrator optical system 7 includes a first lens 71, a second lens 72, a lens array 73, and a third lens 74.

[0020] In the example shown in FIG. 1, the display device 100 approximately collimates each of the laser beams Lr, Lg, and Lb from the laser light source 1 using a collimator lens 5, and then combines the laser beams using a first dichroic mirror 6. The display device 100 approximately uniforms the illuminance of the laser beam L combined by the first dichroic mirror 6 at the position of the spatial modulator 2 using an integrator optical system 7. The display device 100 reflects a part of the laser beam L from the integrator optical system 7 toward the spatial modulator 2 using a prism 8, thereby making the laser beam L incident on the spatial modulator 2. The spatial modulator 2 modulates the spatial polarization distribution of the incident laser beam L, and then emits the modulated laser beam L toward the prism 8. The modulated laser beam L emitted from the spatial modulator 2 is transmitted through the prism 8 and then enters the projection lens 4. The display device 100 projects the modulated laser beam L transmitted through the prism 8 onto a projection surface S such as a screen using the projection lens 4. The display device 100 can display an image on a projection surface S by, for example, modulating the spatial polarization distribution of the laser light L with the spatial modulator 2 and projecting the image onto the projection surface S with the projection lens 4. Note that the image in this specification includes a still image and a moving image.

[0021] In the retardation plate 3, an element functioning as a half-wave plate can be arranged in the first region having birefringence. By arranging the first region so that the optical axis of the first region is inclined by 45 degrees with respect to the polarization direction of the laser light L incident on the first region, the first region can rotate the polarization direction of the incident laser light by 90 degrees and output it. On the other hand, since the second region does not have birefringence, it outputs the incident laser light L without rotating the polarization direction. Therefore, the retardation plate 3 can receive linearly polarized laser light L and output each of the laser lights whose polarization directions are orthogonal to each other. In the example shown in FIG. 1, the retardation plate 3 can receive either P-polarized or S-polarized laser light L and output both P-polarized and S-polarized laser lights.

[0022] Here, in a display device using laser light, speckle noise may occur due to interference between scattered lights of laser light on a projection surface or the like. Speckle noise reduces the quality of a displayed image. As a technology for reducing such speckle noise, a technology is known that includes a birefringent retardation plate and varies the polarization of a part of laser light emitted from a laser light source (see, for example, Patent Document 1). By varying the polarization of a part of the laser light, it is possible to reduce interference between scattered lights of laser light and reduce speckle noise, compared to a case in which the polarization of all the laser light is equal. However, in the technology described in Patent Document 1, since all the regions of the retardation plate have birefringence, the speckle noise reduction performance may be reduced. In the display device 100 according to this embodiment, the retardation plate 3 rotates the polarization direction of the laser light passing through the first region by 90 degrees, and does not rotate the polarization direction of the laser light passing through the second region, among the laser light L emitted from the spatial modulator 2. As a result, the retardation plate 3 can emit each of the laser light whose polarization directions are orthogonal to each other. Laser light whose polarization directions are orthogonal to each other does not interfere with each other. Therefore, in the display device 100, interference between scattered laser beams can be reduced and speckle noise can be reduced, compared to a case where the entire region of the retardation plate has birefringence. In this way, the present embodiment can provide a display device 100 with high speckle noise reduction performance.

[0023] In addition, in the display device 100, the retardation plate 3 can receive either P-polarized or S-polarized laser light L and emit both P-polarized and S-polarized laser light. In the display device 100, since the second region does not have birefringence, the retardation plate 3 can be manufactured more easily than a retardation plate in which both the first and second regions have birefringence.

[0024] Also, some display devices perform display by modulating the spatial polarization distribution of laser light with a liquid crystal layer. In such display devices, since display is performed using polarized light, varying the polarization for the purpose of reducing speckle noise may affect the display. In the display device 100, the polarization of a part of the laser light L after the spatial polarization distribution is modulated by the spatial modulator 2 is varied by the retardation plate 3. Therefore, it is possible to vary the polarization of a part of the laser light L without affecting the display using the modulation of the spatial polarization distribution by the spatial modulator 2. As a result, in this embodiment, in the display device 100 that performs display using the polarized light of the laser light L, speckle noise can be reduced by utilizing the polarized light.

[0025] Moreover, in the display device 100, the projection lens 4 includes a first lens group 41 and a second lens group 42, and the retarder 3 can be disposed between the first lens group 41 and the second lens group 42. By disposing the retarder 3 between the first lens group 41 and the second lens group 42, a phase difference can be imparted by the retarder 3 to a part of the laser light L focused by the first lens group 41. This makes it possible to reduce the area of ​​the retarder 3, making it easier to manufacture the display device 100 and reducing manufacturing costs.

[0026] Furthermore, in the display device 100, the laser light source 1 can emit a plurality of laser beams Lr, Lg, and Lb having mutually different colors. This allows the display device 100 to display a color image generated by modulating the spatial polarization distribution of the laser beam L on the projection surface S with reduced speckle noise.

[0027] 1, the red collimating lens 51 can be made of glass, resin, or the like having a transmittance of 60% or more for the laser light Lr from the red semiconductor laser element 110. The green collimating lens 52 can be made of glass, resin, or the like having a transmittance of 60% or more for the laser light Lg from the green semiconductor laser element 120. The blue collimating lens 53 can be made of glass, resin, or the like having a transmittance of 60% or more for the laser light Lb from the blue semiconductor laser element 130.

[0028] The first red dichroic mirror 61, the first green dichroic mirror 62, and the first blue dichroic mirror 63 can each be a dielectric multilayer mirror or the like whose reflectance and transmittance are adjusted to match the wavelength of the light being reflected and transmitted.

[0029] The first lens 71, the second lens 72, the lens array 73, and the third lens 74 in the integrator optical system 7 can be made of glass or resin having a transmittance of 60% or more for each of the laser light Lr, the laser light Lg, and the laser light Lb. The number of lenses and the lens array included in the integrator optical system 7, their respective shapes, materials, and arrangements, the number of lenses in the lens array, and the like can be changed as appropriate according to the required specifications of the display device 100, and the like.

[0030] For example, LCOS (Liquid Crystal On Silicon) can be used for the spatial modulator 2. LCOS is a reflective liquid crystal element that can modulate and reflect incident light. In the example shown in FIG. 1, the spatial modulator 2 is mounted on a substrate 25. The spatial modulator 2 can generate an image by modulating the spatial polarization distribution of the incident laser light L in response to a drive signal.

[0031] For example, a cube-type beam splitter can be used as the prism 8. Also, a material including glass or the like having a transmittance of 60% or more for each of the laser light Lr, the laser light Lg, and the laser light Lb can be used as the prism 8. A metal film or a dielectric multilayer film with adjusted reflectance and transmittance can be provided on the reflecting surface of the prism 8. A half mirror or the like may be used instead of the prism 8.

[0032] The rotation mechanism 30 includes a motor including an axial member, a gear coupled to the retardation film 3, and the like. The rotation mechanism 30 can rotate the retardation film 3 around the optical axis 40 by transmitting the rotation of the axial member caused by the motor to the retardation film 3 via the gear.

[0033] <Configuration example of projection lens 4> Fig. 2 is a schematic cross-sectional view showing an example of the configuration of the projection lens 4 in the display device 100. Fig. 2 shows a cross section of the projection lens 4 cut by a virtual plane (for example, an XZ plane) including an optical axis 40 of the projection lens 4.

[0034] The first lens group 41 is disposed on the side of the projection lens 4 where the laser light L is incident. The second lens group 42 is disposed on the side of the projection lens 4 where the laser light L is emitted. Each of the first lens group 41 and the second lens group 42 is composed of a plurality of lenses. The number of the plurality of lenses, as well as the shape, material, arrangement, etc. of each lens can be appropriately changed according to the required specifications of the display device 100, etc.

[0035] 2, the projection lens 4 is disposed between a first lens group 41 and a second lens group 42, and has an aperture surface 43 including an aperture 430. The aperture surface 43 can determine the brightness of the projection lens 4 by the diameter of the aperture 430. The aperture 430 may have a fixed diameter, or may have a variable diameter within a predetermined range.

[0036] <Configuration example of retardation plate 3> The configuration of the retardation plate 3 will be described with reference to Figs. 3 to 6. Fig. 3 is a schematic plan view showing a first example of the retardation plate 3. Fig. 4 is a schematic plan view showing the retardation plate 3 rotated from the state shown in Fig. 3. Fig. 5 is a schematic plan view showing the retardation plate 3 rotated from the state shown in Fig. 4. Fig. 6 is a schematic plan view showing a second example of the retardation plate 3. Figs. 3 to 6 show an example of a retardation plate 3 arranged inside an opening 430 in a plan view.

[0037] 3, the retardation plate 3 is a plate-like member having a substantially circular shape in a plan view. The shape of the opening 430 in a plan view is substantially circular. The maximum diameter of the semicircle constituting the retardation plate 3 is smaller than the diameter of the opening 430. This allows the retardation plate 3 to be disposed inside the opening 430. From the viewpoint of reducing speckle noise, it is preferable that the retardation plate 3 is disposed so as to cover the entire opening 430 without any gaps. For example, a retardation plate 3 that is slightly larger than the opening 430 may be disposed so as to cover the entire opening 430.

[0038] In the display device 100, the retarder 3 can include a first region 31 having birefringence and a second region 32 having no birefringence. For example, the first region 31 has birefringence and imparts a phase difference to orthogonal polarization components of the incident light. On the other hand, the second region 32 does not have birefringence and does not impart a phase difference to orthogonal polarization components of the incident light.

[0039] For example, the first region 31 may include a light-transmitting member and a retardation film disposed on the surface of the light-transmitting member. This configuration allows the retardation plate 3 to be easily manufactured. In the example shown in FIG. 3, the shape of the first region 31 in plan view is approximately semicircular. The shape of the second region 32 in plan view is approximately semicircular with a curved portion located on the opposite side to the semicircle of the first region 31. The light-transmitting member may be configured to include glass or resin having a transmittance of 60% or more for the laser light L. The retardation film may be a resin film having birefringence that functions as a half-wave plate. The first region 31 may be configured, for example, by attaching or applying a retardation film to the surface of the light-transmitting member.

[0040] The retardation film constituting the first region 31 is disposed with its optical axis tilted at 45 degrees with respect to the polarization direction of the laser light L incident on the first region 31. The first region 31 rotates the polarization of the laser light L by 90 degrees by imparting a phase difference to the orthogonal polarization components of the laser light L transmitted through the first region 31. On the other hand, the polarization direction of the laser light L transmitted through the second region 32 does not change. Since the area of ​​the first region 31 and the area of ​​the second region 32 are almost equal, the amount of the laser light L passing through the first region 31 and the amount of the laser light L passing through the second region 32 are almost equal. As a result, the retardation plate 3 can emit laser light L polarized in two orthogonal directions with almost equal light amounts based on the linearly polarized laser light L incident thereon.

[0041] Orthogonal polarized lights do not interfere with each other. Therefore, in the display device 100, speckle noise caused by interference between laser lights scattered on a projection surface such as a screen can be reduced compared to a case where the polarization of the laser light L from the spatial modulator 2 is not changed by the retardation plate 3. Note that in FIG. 3, the area of ​​the first region 31 and the area of ​​the second region 32 do not necessarily have to be equal, and the area ratio can be changed as appropriate.

[0042] 3, the retardation plate 3 can be disposed inside the opening 430 in the diaphragm surface 43. Almost all of the laser light L from the spatial modulator 2 passes through the opening 430 in a focused state. Therefore, by disposing the retardation plate 3 inside the opening 430, the area of ​​the retardation plate 3 can be reduced. This makes it easier to manufacture the display device 100 and reduces manufacturing costs.

[0043] A more detailed explanation will be given below. For example, compared to arranging the retardation plate 3 downstream of the projection lens 4 in the traveling direction of the laser light L (a position after the laser light L is emitted from the projection lens 4) or arranging the retardation plate 3 upstream of the projection lens 4 in the traveling direction of the laser light L (a position before the laser light L is incident on the projection lens 4), by arranging the retardation plate 3 inside the opening 430 in the diaphragm surface 43 of the projection lens 4, the following effects (1) to (3) can be obtained. (1) When the retardation plate 3 is disposed on the upstream or downstream side of the projection lens 4 in the traveling direction of the laser light L, the diameter of the light beam passing through the region near the optical axis 40 of the projection lens 4 differs from that passing through the region away from the optical axis 40 of the projection lens 4, and therefore, bias may occur in the phase difference imparted by the retardation plate 3. By disposing the retardation plate 3 inside the opening 430 in the diaphragm surface 43 of the projection lens 4, it is possible to impart a uniform phase difference for each different image height with respect to the optical axis 40 of the projection lens 4. (2) When the retardation plate 3 is disposed on the upstream or downstream side of the projection lens 4 in the traveling direction of the laser light L, the first region 31 and the second region 32 must be subdivided in accordance with the diameter of the light beam, which may increase the manufacturing cost of the retardation plate 3. By disposing the retardation plate 3 inside the opening 430 in the diaphragm surface 43 of the projection lens 4, the subdivision of the first region 31 and the second region 32 is suppressed, and an increase in the manufacturing cost of the retardation plate 3 can be avoided. (3) By disposing the retardation plate 3 inside the opening 430 in the diaphragm surface 43 of the projection lens 4, the area of ​​the retardation plate 3 can be reduced, and the display device 100 can be made smaller.

[0044] However, the position where the retardation plate 3 is disposed is not limited to the inside of the opening 430, as long as a phase difference can be imparted to some orthogonal polarization components of the laser light L emitted from the spatial modulator 2. For example, the retardation plate 3 may be disposed between the prism 8 and the projection lens 4, on the +Z side or -Z side of the diaphragm surface 43 between the first lens group 41 and the second lens group 42, between the projection lens 4 and the projection surface S, or the like.

[0045] Furthermore, in the display device 100, the retardation plate 3 can rotate by 90 degrees the polarization direction of half of the laser light L from the spatial modulator 2. This can improve the performance of reducing speckle noise.

[0046] The retardation plate 3 may be composed of only the first region 31 that imparts a phase difference to the orthogonal polarization components of the incident light. In this case, the shape of the retardation plate 3 in plan view is approximately semicircular. In the example shown in FIG. 3, the retardation plate 3 is disposed so as to cover approximately half of the opening 430 that is approximately circular in plan view. The retardation plate 3 can impart a phase difference to the orthogonal polarization components of the laser light L that passes through the retardation plate 3, among the laser light L that passes through the opening 430.

[0047] Moreover, in the display device 100, the retarder 3 can rotate the polarization direction of the laser light L passing through the first region 31 by 90 degrees while being rotated by the rotation mechanism 30. In the example shown in Fig. 4 and Fig. 5, the display device 100 changes the region where the opening 430 and the first region 31 of the retarder 3 overlap by rotating the retarder 3 around the optical axis 40 by the rotation mechanism 30. Then, of the laser light L passing through the opening 430, the retarder 3 can change the laser light L passing through the first region 31. This can further reduce speckle noise by a time multiplexing effect in which the state of the laser light L changes over time.

[0048] In the display device 100, in the example shown in FIG. 6, the first regions 31 and the second regions 32 may be alternately arranged in two orthogonal directions (e.g., X direction and Y direction) in the incident surface 33 (e.g., a direction along the XY plane) of the retarder 3 on which the laser light L is incident. Furthermore, the first regions 31 and the second regions 32 may be alternately arranged in one direction (e.g., X direction or Y direction) in the incident surface 33 of the retarder 3 on which the laser light L is incident, that is, arranged in a stripe shape. With these arrangements, speckle noise can be reduced compared to a case in which the polarization of the laser light L from the spatial modulator 2 is not varied by the retarder 3. Furthermore, by making the sum of the areas of the first regions 31 and the sum of the areas of the second regions 32 approximately equal, speckle noise can be reduced compared to a case in which the polarization of the laser light L from the spatial modulator 2 is not varied by the retarder 3. Furthermore, by rotating the retarder 3 around the optical axis 40, speckle noise can be further reduced by the time multiplexing effect.

[0049] A retardation plate 3 in which a plurality of first regions 31 and a plurality of second regions 32 are alternately arranged in each of two orthogonal directions can be produced by attaching or applying a retardation film to the surface of a light-transmitting member. A retardation plate 3 in which a plurality of first regions 31 and a plurality of second regions 32 are alternately arranged in one direction can also be produced by attaching or applying a retardation film to the surface of a light-transmitting member.

[0050] In the examples shown in Figs. 1 to 6, the retardation plate 3 is rotated by the rotation mechanism 30, but the present invention is not limited thereto. For example, a piezoelectric actuator or the like is used as a driving unit to vibrate the retardation plate 3, thereby obtaining a speckle noise reduction effect due to a time multiplexing effect. For example, a retardation plate in which the first regions 31 and the second regions 32 are arranged in a matrix as illustrated in Fig. 6, or a retardation plate in which the first regions 31 and the second regions 32 are arranged in a stripe pattern, etc., do not need to be rotated. From the viewpoint of increasing the speckle noise reduction effect by varying the polarization, it is preferable to vibrate in a direction in which the first regions 31 and the second regions 32 are arranged alternately.

[0051] [Second embodiment] Next, a display device according to a second embodiment will be described. Note that the same names and symbols as those in the already described embodiments indicate the same or similar members or configurations, and detailed descriptions will be omitted as appropriate. This also applies to the following embodiments.

[0052] Fig. 7 is a schematic cross-sectional view showing an example of a display device 100a according to a second embodiment. Fig. 7 shows a cross section of the display device 100a cut along a virtual plane (e.g., an XZ plane) including the optical axis 40 of the projection lens 4. The display device 100a is, for example, a projector.

[0053] The present embodiment differs from the first embodiment mainly in that it has a red spatial modulator 2r, a green spatial modulator 2g, and a blue spatial modulator 2b for each of the red, green, and blue components of the laser light L. With this configuration, the spatial polarization distribution can be modulated for each color component of the laser light L, improving the color reproducibility of the modulated laser light L and the color reproducibility of the image projected on the projection surface S. Other effects and advantages are the same as those of the first embodiment.

[0054] 7, the laser light L emitted from the laser light source 1 passes through a collimator lens 5, a first dichroic mirror 6, and an integrator optical system 7, and is then reflected by a first mirror 9. Of the laser light L reflected by the first mirror 9, a red component is reflected by a second dichroic mirror 10, and green and blue components are transmitted by the second dichroic mirror 10.

[0055] The red component of the laser light L reflected by the second dichroic mirror 10 is reflected by the second red dichroic prism 12r and enters the red spatial modulator 2r. The red spatial modulator 2r modulates the spatial polarization distribution of the red component of the incident laser light L and reflects it toward the second red dichroic prism 12r. The red component of the laser light L reflected by the red spatial modulator 2r is transmitted through the second red dichroic prism 12r and then enters the dichroic prism 13.

[0056] Of the green and blue components of the laser light L transmitted by the second dichroic mirror 10, the green component is reflected by the second green dichroic prism 12g and enters the green spatial modulator 2g. The green spatial modulator 2g modulates the spatial polarization distribution of the green component of the incident laser light L and reflects it toward the second green dichroic prism 12g. The green component of the laser light L reflected by the green spatial modulator 2g is transmitted by the second green dichroic prism 12g and then enters the dichroic prism 13.

[0057] Of the green and blue components of the laser light L transmitted by the second dichroic mirror 10, the blue component is transmitted by the second blue dichroic prism 12b and reflected by the second mirror 11. The blue component is then reflected by the second blue dichroic prism 12b and enters the blue spatial modulator 2b. The blue spatial modulator 2b modulates the spatial polarization distribution of the blue component of the incident laser light L and reflects it toward the second blue dichroic prism 12b. The blue component of the laser light L reflected by the blue spatial modulator 2b is transmitted by the second blue dichroic prism 12b and then enters the dichroic prism 13.

[0058] The dichroic prism 13 reflects each of the red and blue components of the modulated laser light L toward the projection lens 4, and transmits the green component of the modulated laser light L. This allows the dichroic prism 13 to combine the red, green, and blue components of the modulated laser light L. The projection lens 4 can project the laser light L, which is a combination of the red, green, and blue components, onto the projection surface S.

[0059] The second mirror 11 and the first mirror 9 may be made of a material having a metal film or the like provided on a base material. The second dichroic mirror 10, the second red dichroic prism 12r, the second green dichroic prism 12g, the second blue dichroic prism 12b, and the dichroic prism 13 may be made of a material including glass or the like having a transmittance of 60% or more for each of the laser light Lr, the laser light Lg, and the laser light Lb. The reflecting surfaces of the second dichroic mirror 10, the second red dichroic prism 12r, the second green dichroic prism 12g, the second blue dichroic prism 12b, and the dichroic prism 13 may be provided with a dielectric multilayer film or the like whose reflectance and transmittance are adjusted according to the wavelength of the light reflected and transmitted.

[0060] [Third embodiment] Next, a display device according to a third embodiment will be described.

[0061] Fig. 8 is a schematic cross-sectional view showing an example of a display device 100b according to a third embodiment. Fig. 8 shows a cross section of the display device 100b cut along a virtual plane (e.g., an XZ plane) including the optical axis 40 of the projection lens 4. The display device 100b is, for example, a projector.

[0062] This embodiment differs from the first embodiment mainly in that a transmissive liquid crystal element 2B is used as the spatial modulator 2, and that a red transmissive liquid crystal element 2Br, a green transmissive liquid crystal element 2Bg, and a blue transmissive liquid crystal element 2Bb are provided for the red, green, and blue components of the laser light L. With this configuration, the spatial polarization distribution can be modulated for each color component of the laser light L, thereby improving the color reproducibility of the modulated laser light L and the color reproducibility of the image projected on the projection surface S. Other effects and advantages are the same as those of the first embodiment.

[0063] 8, the laser light L emitted from the laser light source 1 passes through a collimator lens 5, a first dichroic mirror 6, and an integrator optical system 7, and is then reflected by a first mirror 9. Of the laser light L reflected by the first mirror 9, a red component is reflected by a second dichroic mirror 10, and green and blue components are transmitted by the second dichroic mirror 10.

[0064] The red component of the laser light L reflected by the second dichroic mirror 10 is reflected by the third red dichroic mirror 14r and enters the red transmissive liquid crystal element 2Br. The third red dichroic mirror 14r may be a simple mirror that does not have wavelength selectivity. The red transmissive liquid crystal element 2Br transmits the red component of the incident laser light L while modulating the spatial polarization distribution. The red component of the laser light L transmitted by the red transmissive liquid crystal element enters the dichroic prism 13.

[0065] Of the green and blue components of the laser light L transmitted by the second dichroic mirror 10, the green component is reflected by the third green dichroic mirror 14g and enters the green transmissive liquid crystal element 2Bg. The green transmissive liquid crystal element 2Bg transmits the green component of the incident laser light L while modulating the spatial polarization distribution. The green component of the laser light L transmitted by the green transmissive liquid crystal element 2Bg enters the dichroic prism 13.

[0066] Of the green and blue components of the laser light L transmitted by the second dichroic mirror 10, the blue component is reflected by the third blue dichroic mirror 14b, and then reflected by the third mirror 15, and then enters the blue transmissive liquid crystal element 2Bb. The third blue dichroic mirror 14b may be a simple mirror that does not have wavelength selectivity. The blue transmissive liquid crystal element 2Bb transmits the laser light L while modulating the spatial polarization distribution of the blue component. The blue component of the laser light L transmitted by the blue transmissive liquid crystal element 2Bb enters the dichroic prism 13.

[0067] The dichroic prism 13 reflects each of the red and blue components of the modulated laser light L toward the projection lens 4, and transmits the green component of the modulated laser light L, thereby combining the red, green, and blue components of the modulated laser light L. The projection lens 4 can project the laser light L, which is a combination of the red, green, and blue components, onto the projection surface S.

[0068] The third red dichroic mirror 14r, the third green dichroic mirror 14g, and the third blue dichroic mirror 14b may be made of glass or the like having a transmittance of 60% or more for the laser light L. The reflective surfaces of the third red dichroic mirror 14r, the third green dichroic mirror 14g, and the third blue dichroic mirror 14b may be provided with a dielectric multilayer film or the like whose reflectance and transmittance are adjusted according to the wavelength of the light to be reflected and transmitted.

[0069] [Fourth embodiment] Next, a head mounted display according to a fourth embodiment will be described.

[0070] Fig. 9 is a schematic cross-sectional view showing an example of a head mounted display 200 according to a fourth embodiment. Fig. 9 shows a cross section of the head mounted display 200 cut by a virtual plane (for example, an XZ plane) including the optical axis 40 of the projection lens 4.

[0071] The head mounted display 200 according to this embodiment differs from the first embodiment mainly in that it includes a display device 100 and a light guide plate 17. The head mounted display 200 also provides the same effects as the first embodiment.

[0072] The head mounted display 200 is a display device that is worn on the head of a wearer U of the head mounted display 200 and displays an image that is visible to the wearer U. For example, the display device 100 is disposed on a support part or the like of a glasses-type support body. The light guide plate 17 is disposed on a lens holding part or the like of the glasses-type support body.

[0073] 9, the laser light L emitted from the laser light source 1 passes through a collimator lens 5, a first dichroic mirror 6, and an integrator optical system 7, and is then reflected by a first mirror 9. The laser light L reflected by the first mirror 9 passes through a field lens 16 and is reflected by a prism 8 toward the spatial modulator 2.

[0074] The laser light L reflected by the prism 8 is transmitted by the prism 8 and enters the projection lens 4. The projection lens 4 projects the laser light L from the prism 8 towards the light guide plate 17.

[0075] Light guide plate 17 is a plate-like member including a resin, glass, or the like having a transmittance of 60% or more for laser light L. Light guide plate 17 includes a first main surface 171, a second main surface 172 disposed on the opposite side to first main surface 171, and a light guide section 173 and a light extraction section 174 disposed on second main surface 172.

[0076] The laser light L projected by the projection lens 4 is incident on the inside of the light guide plate 17 through a portion of the first main surface 171 facing the projection lens 4. The light guide section 173 is, for example, a diffraction grating having a periodic structure. The light guide section 173 is disposed on a portion of the second main surface 172 that is located on the opposite side to the portion of the first main surface 171 facing the projection lens 4. In the light guide section 173, the periodic structure of the diffraction grating may be formed directly on the second main surface 172, or a film or plate-like member on which a diffraction grating is formed may be provided on the second main surface 172.

[0077] The light guiding section 173 diffracts the laser light L incident on the inside of the light guiding plate 17 through a portion of the first main surface 171 facing the projection lens 4, thereby guiding the light toward the side where the light extraction section 174 is located (for example, the +Z side). The laser light L diffracted by the light guiding section 173 is guided inside the light guiding plate 17 toward the side where the light extraction section 174 is located while being totally reflected by each of the first main surface 171 and the second main surface 172. Note that the light guiding section 173 is not limited to a diffraction grating, and may be a reflective surface that reflects the incident laser light L and guides the light to the side where the light extraction section 174 is located.

[0078] The light extraction unit 174 diffracts, reflects, or scatters the laser light L that reaches the light extraction unit 174, out of the laser light L guided inside the light guide plate 17, toward the eye of the wearer U of the head mounted display 200. The laser light L diffracted, reflected, or scattered by the light extraction unit 174 is extracted from the inside of the light guide plate 17 to the outside through the first main surface 171, and is incident on the eye of the wearer U. The wearer U can visually recognize an image based on the laser light L incident on his or her eye.

[0079] When diffracting the laser light L, a diffraction grating or the like can be used for the light extraction unit 174. When reflecting the laser light L, a mirror or a prism or the like can be used for the light extraction unit 174. When scattering the laser light L, a rough surface such as a textured surface can be used for the light extraction unit 174. As the mirror or prism, a micromirror array including a plurality of minute mirrors, a microprism array including a plurality of minute prisms, or the like can be used.

[0080] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0081] The ordinal numbers, quantities, and other numbers used in the description of the embodiments are all provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present disclosure, and do not limit the connection relationships that realize the functions of the present disclosure.

[0082] The display device of the present disclosure is a display device that uses polarized laser light to display an image, and can reduce speckle noise by using polarization, and therefore can be suitably used in projectors, head-mounted displays, rear projectors, head-up displays, and the like that use laser light.

[0083] Aspects of the present disclosure are, for example, as follows. <Item 1> A display device comprising: a laser light source that emits linearly polarized laser light; a spatial modulator that modulates the spatial polarization distribution of the laser light emitted from the laser light source; and a retardation plate that includes a first region having birefringence and a second region not having birefringence, and that rotates by 90 degrees the polarization direction of the laser light that passes through the first region out of the laser light emitted from the spatial modulator. <Item 2> The display device according to <Item 1>, wherein the retardation plate receives either P-polarized or S-polarized laser light and emits both P-polarized and S-polarized laser light. <Item 3> The display device according to <Item 1> or <Item 2>, further comprising a projection lens that projects the laser light from the spatial modulator, the projection lens including a first lens group and a second lens group, and the retardation plate being disposed between the first lens group and the second lens group. <Item 4> The display device described in <Item 3>, wherein the projection lens is disposed between the first lens group and the second lens group and has an aperture surface including an aperture, and the retardation plate is disposed inside the opening on the aperture surface. <Item 5> The display device according to <Item 3> or <Item 4>, further comprising a rotation mechanism that rotates the retardation plate around an optical axis of the projection lens, and the retardation plate rotates a polarization direction of laser light passing through the first region by 90 degrees while being rotated by the rotation mechanism. <Item 6> The display device according to any one of <Item 1> to <Item 5>, wherein the retardation plate rotates the polarization direction of half of the laser light from the spatial modulator by 90 degrees. <Item 7> The display device according to any one of <Item 1> to <Item 6>, wherein the laser light source emits a plurality of laser beams having mutually different colors. <Item 8> The display device according to any one of <Item 1> to <Item 7>, wherein the retardation plate includes a plurality of the first regions and a plurality of the second regions. <Item 9> The display device according to <Item 8>, wherein the first region includes a translucent member and a retardation film arranged on a surface of the translucent member, and the second region includes the translucent member. <Item 10> The display device according to <Item 8> or <Item 9>, wherein a plurality of the first regions and a plurality of the second regions are alternately arranged in each of two perpendicular directions within an incident surface of the retardation plate into which the laser light is incident. <Item 11> A projector is the display device according to any one of <Item 1> to <Item 10>. [Explanation of symbols]

[0084] 1 Laser light source 110 Red semiconductor laser element 120 Green semiconductor laser element 130 Blue semiconductor laser element 2 Spatial Modulator 2r Red spatial modulator 2g Green spatial modulator 2b Blue spatial modulator 2B Transmissive liquid crystal element 2Br Red transmissive liquid crystal element 2Bg Green transmissive liquid crystal element 2Bb Blue transmissive liquid crystal element 25 Substrate 3 Retardation plate 30 Rotation mechanism 31 First area 32 Second area 33 Incidence plane 4 Projection Lens 40 Optical axis 41 First lens group 42 Second lens group 43 Aperture surface 430 Aperture 5 Collimating Lens 51 Red collimating lens 52 Green collimating lens 53 Blue collimating lens 6. 1st dichroic mirror 61 1st red dichroic mirror 62 1st green dichroic mirror 63 1st Blue Dichroic Mirror 7 Integrator optical system 71 First lens 72 Second lens 73 Lens Array 74 Third Lens 8. Prism 9. Mirror No. 1 10 2nd dichroic mirror 11 2nd Mirror 12r 2nd Red Dichroic Prism 12g 2nd Green Dichroic Prism 12b 2nd Blue Dichroic Prism 13 Dichroic Prism 14r 3rd red dichroic mirror 14g 3rd Green Dichroic Mirror 14b 3rd blue dichroic mirror 15 3rd Mirror 16 Field Lens 17 Light guide plate 171 First main surface 172 Second main surface 173 Light guide section 174 Light extraction section L Laser light Lr Red laser light Lg green laser light Lb Blue laser light S projection surface

Claims

1. a laser light source that emits linearly polarized laser light; a spatial modulator that modulates a spatial polarization distribution of the laser light emitted from the laser light source; A display device comprising: a first region having birefringence and a second region not having birefringence; and a retardation plate that rotates by 90 degrees the polarization direction of laser light that passes through the first region out of laser light emitted from the spatial modulator.

2. 2. The display device according to claim 1, wherein the retardation plate receives either P-polarized or S-polarized laser light and emits both P-polarized and S-polarized laser light.

3. a projection lens for projecting the laser light from the spatial modulator; the projection lens includes a first lens group and a second lens group, The display device according to claim 1 , wherein the retardation plate is disposed between the first lens group and the second lens group.

4. the projection lens is disposed between the first lens group and the second lens group, and has a diaphragm surface including an aperture; The display device according to claim 3 , wherein the retardation plate is disposed inside the opening in the diaphragm surface.

5. a rotation mechanism for rotating the retardation plate around an optical axis of the projection lens, The display device according to claim 3 , wherein the retardation plate rotates a polarization direction of the laser light passing through the first region by 90 degrees while being rotated by the rotation mechanism.

6. 2. The display device according to claim 1, wherein the phase difference plate rotates the polarization direction of half of the laser light from the spatial modulator by 90 degrees.

7. The display device according to claim 1 , wherein the laser light source emits a plurality of laser beams having mutually different colors.

8. The display device according to claim 1 , wherein the retardation plate includes a plurality of the first regions and a plurality of the second regions.

9. the first region includes a light-transmitting member and a retardation film disposed on a surface of the light-transmitting member, The display device according to claim 8 , wherein the second region includes the light-transmitting member.

10. The display device according to claim 8 , wherein the first regions and the second regions are alternately arranged in two directions perpendicular to each other within an incident surface of the retardation plate onto which the laser light is incident.

11. A projector, which is the display device according to any one of claims 1 to 10.

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