projector

Abstract

To provide a small projector that can reduce speckle noise.SOLUTION: The projector of the present invention includes: a light source for emitting a laser beam; a meta-surface element for modulating the phase of the laser beam emitted from the light source; and an optical modulation element for modulating the laser beam emitted from the meta-surface element and having a modulated phase and generating the incident light.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present invention relates to a projector. [Background technology]

[0002] In recent years, semiconductor lasers (laser diodes; LDs), which have advantages such as high brightness, long life, and a narrow beam angle, have been used as light sources for image display devices such as projectors. While using LDs as light sources provides the above-mentioned advantages, the laser light projected and scattered on the screen of the image display device interferes on the observer's retina due to the influence of higher coherence than conventional white light sources, etc., resulting in speckle noise.

[0003] For example, Patent Document 1 discloses an apparatus including a light source that emits coherent light. The apparatus disclosed in Patent Document 1 further includes a projection optical unit that projects light from the light source onto a screen, an image forming device that modulates the coherent light to form an image, and a phase modulation unit that modulates the phase of the coherent light. The image forming device and the phase modulation unit are disposed between the light source and the projection optical unit. The phase modulation unit includes, for example, a drive unit that changes interference fringes formed on the screen by interference between coherent light that has passed through a high refractive index portion and a low refractive index portion, faster than can be seen by the human eye. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-059265 Summary of the Invention [Problem to be solved by the invention]

[0005] One aspect of the phase modulation unit of the device disclosed in the aforementioned Patent Document 1 has a cylindrical main body and a rotation axis connected to the center of the main body. The cylindrical main body is made of a low refractive index material, and particles dispersed on the side of the main body are made of a high refractive index material having a higher refractive index than the low refractive index material. However, if the phase modulation unit is arranged between the light source and the projection optical unit so that the axis and rotation axis of the main body cross the optical path of the coherent light in order to reduce speckle noise on the screen, an installation space at least larger than the diameter of the bottom of the main body is required, which could result in an increase in the size of the entire device. [Means for solving the problem]

[0006] In order to solve the above problems, one embodiment of a projector of the present invention comprises a light source, a metasurface element that modulates the phase of light emitted from the light source, and a light modulation element that modulates the phase-modulated light emitted from the metasurface element to generate image light. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic configuration diagram of a projector according to a first embodiment. [Figure 2] FIG. 1 is a schematic configuration diagram of a light source module according to a first embodiment. [Figure 3A] FIG. 3 is a side view of the metasurface element of the light source module shown in FIG. 2. [Figure 3B] FIG. 3B is a plan view of the metasurface element shown in FIG. 3A. [Figure 4A] FIG. 3B is a side view of a first modified example of the metasurface element shown in FIG. 3A. [Figure 4B] FIG. 4B is a plan view of the metasurface element shown in FIG. 4A. [Figure 5] FIG. 3B is a side view of a second modified example of the metasurface element shown in FIG. 3A. [Figure 6] FIG. 3B is a side view of a third modified example of the metasurface element shown in FIG. 3A. [Figure 7]FIG. 3 is a side view of a metasurface element of a second embodiment applicable to the light source module shown in FIG. 2. [Figure 8A] FIG. 8 is a side view of a first modified example of the metasurface element shown in FIG. 7. [Figure 8B] FIG. 8B is a plan view of the metasurface element shown in FIG. 8A. [Figure 9] FIG. 8 is a side view of a second modified example of the metasurface element shown in FIG. 7. [Figure 10] FIG. 8 is a side view of a third modified example of the metasurface element shown in FIG. 7. [Figure 11] FIG. 3 is a side view of a metasurface element of a third embodiment applicable to the light source module shown in FIG. 2. [Figure 12] FIG. 12 is a side view of a second modified example of the metasurface element shown in FIG. [Figure 13] FIG. 12 is a side view of a third modified example of the metasurface element shown in FIG. [Figure 14] FIG. 10 is a schematic configuration diagram of a projector according to a fourth embodiment. [Figure 15] FIG. 10 is a schematic configuration diagram of a light source module according to a fourth embodiment. [Figure 16] This is a side view showing the configuration of a metasurface element of a fourth embodiment that can be applied to the light source module shown in Figure 15 and the behavior of blue laser light when blue laser light is incident on the metasurface element. [Figure 17] This is a side view showing the behavior of yellow light when it is incident on the metasurface element shown in Figure 16. [Figure 18] 17 is a graph showing an example of the relationship between the width and phase of the microstructure of the metasurface element shown in FIG. 16. [Figure 19] 17 is a graph showing an example of the phase distribution of the metasurface element shown in FIG. 16. [Figure 20] FIG. 10 is a schematic configuration diagram of a light source module according to a fifth embodiment. [Figure 21]This is a side view showing the configuration of a metasurface element of a fifth embodiment that can be applied to the light source module shown in Figure 20 and the behavior of blue laser light when blue laser light is incident on the metasurface element. [Figure 22] 22 is a schematic diagram of the spectral distribution of blue laser light incident on the metasurface element shown in FIG. 21. [Figure 23] 22 is a schematic diagram of the spectral distribution of blue laser light emitted from the metasurface element shown in FIG. 21. [Figure 24] FIG. 10 is a side view of the metasurface element of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] [First embodiment] A first embodiment of the present invention will be described below with reference to FIGS. 1 to 8B.

[0009] (projector) 1 is a schematic configuration diagram of a projector 100 according to a first embodiment. Note that in the following drawings, the scale of the dimensions of some components may be changed to make the components easier to see.

[0010] 1, the projector 100 is a projection-type image display device that projects an image onto a screen SCR. The projector 100 includes three light source modules, namely, a first light source module 1R for red, a second light source module 1G for green, and a third light source module 1B for blue, a cross dichroic prism 3, and a projection optical system (projection device) 4.

[0011] The first light source module 1R emits red image light LR. The second light source module 1G emits green image light LG. The third light source module 1B emits blue image light LB. The first light source modules 1R, 1G, and 1B form red, green, and blue image light LR, LG, and LB, respectively, according to information on pixels corresponding to each optical system of the target image to be displayed by the projector 100.

[0012] The image lights LR, LG, and LB emitted from the first light source module 1R, second light source module 1G, and third light source module 1B are incident on the cross dichroic prism 3. The cross dichroic prism 3 combines the image lights LR, LG, and LB and guides them to the projection optical system 4. The projection optical system 4 enlarges the image formed by the first light source modules 1R, 1G, and 1B and projects it onto a screen SCR. The projection optical system 4 is composed of one or more projection lenses.

[0013] The cross dichroic prism 3 is formed by bonding four right-angle prisms together and has a dielectric multilayer film that reflects red light and a dielectric multilayer film that reflects blue light. The three color image lights LR, LG, and LB are combined by the dielectric multilayer film to form light LL that represents a color image.

[0014] Hereinafter, the direction parallel to the optical axis of light LL emitted from the cross dichroic prism 3 will be referred to as the Z direction, the forward side of the traveling direction of light LL in the Z direction will be referred to as the +Z side, and the side opposite the +Z side in the Z direction will be referred to as the -Z side. Furthermore, the direction perpendicular to the Z direction will be referred to as the X direction, one side relative to the X direction will be referred to as the +X side, and the other side relative to the X direction will be referred to as the -X side. Furthermore, the direction perpendicular to both the X and Z directions will be referred to as the Y direction, one side relative to the Y direction will be referred to as the +Y side, and the other side relative to the Y direction will be referred to as the -Y side.

[0015] When viewed along the Y direction, the interfaces between the rectangular prisms of the cross dichroic prism 3 are formed in the shape of a cross. A dielectric multilayer film that reflects blue image light LB and transmits green image light LG and red image light LR is disposed at the interfaces that move from the -X side to the +X side as they progress from the -Z side to the +Z side. A dielectric multilayer film that reflects red image light LR and transmits green image light LG and blue image light LB is disposed at the interfaces that move from the +X side to the -X side as they progress from the -Z side to the +Z side.

[0016] The third light source module 1B is disposed opposite in the X direction to a side surface 3b of the cross dichroic prism 3 that is parallel to the Z direction on the -X side, and is disposed on the -X side of the cross dichroic prism 3. The image light LB emitted from the third light source module 1B is incident on the side surface 3b of the cross dichroic prism 3 from the -X side parallel to the X direction.

[0017] The first light source module 1R is disposed opposite in the X direction a side surface 3r that is parallel to the Z direction on the +X side of the cross dichroic prism 3, and is disposed on the +X side of the cross dichroic prism 3. The image light LR emitted from the first light source module 1R is incident on the side surface 3r of the cross dichroic prism 3 from the +X side parallel to the X direction.

[0018] The second light source module 1G is disposed opposite in the Z direction to a side surface 3g that is parallel to the X direction on the -Z side of the cross dichroic prism 3, and is disposed on the -Z side of the cross dichroic prism 3. The image light LG emitted from the second light source module 1G is incident on the side surface 3g of the cross dichroic prism 3 from the -Z side parallel to the Z direction.

[0019] The projection optical system 4 is disposed opposite side surface 3m of the cross dichroic prism 3 in the Z direction, which is parallel to the X direction, on the +Z side of the cross dichroic prism 3, and is disposed on the +Z side of the cross dichroic prism 3. The screen SCR is disposed opposite side surface 3m of the cross dichroic prism 3 in the Z direction, and is disposed at a predetermined position further +Z on the +Z side of the projection optical system 4. The light LL combined by the cross dichroic prism 3 is emitted toward the +Z side along the Z direction and projected onto the screen SCR by the projection optical system 4. An enlarged image is displayed on the screen SCR.

[0020] Although the colors of light emitted by the first light source modules 1R, 1G, and 1B, i.e., the wavelength bands of the image lights LR, LG, and LR, are different from one another, the first light source modules 1R, 1G, and 1B have the same configuration. Below, of the first light source modules 1R, 1G, and 1B, the third light source module 1B will be taken as an example and the configuration of the third light source module 1B will be described in detail.

[0021] (light source module) Fig. 2 is a schematic configuration diagram of a third light source module 1B of the first embodiment. As shown in Fig. 2, the third light source module 1B includes a light source unit 10, a condenser lens 21, a diffusion element 30, a pickup optical system 40, a despeckle element 201, a first lens array 50, a second lens array 60, a polarization conversion element 70, superimposing lenses 81 and 82, a field lens 90B, and a light modulation element 95B. In the third light source module 1B, the above-mentioned components are arranged in the order shown from the -X side to the +X side along the X direction. In this embodiment, the light source module includes a light source unit 10, a condensing lens 21, a diffusion element 30, a pickup optical system 40, a despeckle element 201, a first lens array 50, a second lens array 60, a polarization conversion element 70, superimposing lenses 81 and 82, a field lens 90B, and a light modulation element 95B, but this is not limited thereto, and it is sufficient that the projector 100 includes a light source unit 10, a condensing lens 21, a diffusion element 30, a pickup optical system 40, a despeckle element 201, a first lens array 50, a second lens array 60, a polarization conversion element 70, superimposing lenses 81 and 82, a field lens 90B, and a light modulation element 95B.

[0022] The light source unit 10 includes a substrate (base material) 11, a plurality of LD light sources (light sources) 12, and a plurality of microlenses 14. The substrate 11 has a plate surface extending parallel to a YZ plane including the Y and Z directions, and has a predetermined thickness in the X direction. The plurality of LD light sources 12 are arranged at intervals from each other on the plate surface on the +X side of the substrate 11. The LD light source 12 emits blue laser light (light) B having a blue wavelength band. The blue wavelength band may be any wavelength band required for blue image light LB in the visible wavelength band, for example, a wavelength band within the range of 400 nm to 470 nm. The number of LD light sources 12 is not limited to a specific number and is determined appropriately depending on the light intensity required for the image light LB and the light intensity of blue laser light B emitted from one LD light source.

[0023] Two microlenses 14 are arranged on the +X side of each LD light source 12. The two microlenses 14 collimate the blue laser light B emitted from the LD light source 12 to the +X side along the X direction, and further emit it to the +X side along the X direction. The number of microlenses 14 arranged corresponding to each LD light source 12 may be one, or may be three or more, and is set as appropriate.

[0024] The light source unit 10 emits blue laser light B, which is collimated along the X direction by the plurality of LD light sources 12 and the plurality of microlenses 14 and is made up of a plurality of light beams, to the +X side.

[0025] Condenser lens 21 is arranged at a predetermined interval in the X direction from a plurality of microlenses 14 arranged on the +X side of light source unit 10, and is arranged on the +X side of these microlenses 14. Condenser lens 21 collectively emits blue laser light B made up of a plurality of light beams emitted from light source unit 10 to the +X side, and condenses the light at a predetermined position on diffusion element 30. Condenser lens 21 is formed of, for example, a biconvex lens.

[0026] The diffusion element 30 is disposed at a predetermined distance from the condenser lens 21 in the X direction and on the +X side of the condenser lens 21. The diffusion element 30 includes a diffusion plate 31 and a motor 32. The diffusion plate 31 is formed in a disk shape and has a plate surface extending parallel to the YZ plane. At least one plate surface of the diffusion plate 31 is formed with a microstructure capable of diffusing the blue laser light B incident in a condensed state. The motor 32 rotates the diffusion plate 31 in the YZ plane around a rotation axis RX. The rotation axis RX is located on the -Z side of the optical axis AX1 of the blue laser light B.

[0027] Blue laser light B emitted from condenser lens 21 is condensed on the plate surface of diffuser plate 31, which rotates around rotation axis RX, on the +Z side of rotation axis RX, and is diffused by the fine structure of diffuser plate 31. The diffused blue laser light B is emitted toward the +X side of diffuser plate 31 along the X direction.

[0028] The pickup optical system 40 is disposed at a predetermined distance in the X direction from the diffusion plate 31 of the diffusion element 30 and on the +X side of the diffusion plate 31. The pickup optical system 40 includes, for example, a first lens 41 and a second lens 42. The first lens 41 and the second lens 42 are disposed adjacent to each other in the X direction. The second lens 42 is disposed on the +X side of the first lens 41. Each of the first lens 41 and the second lens 42 is formed of, for example, a biconvex lens. The number of lenses included in the pickup optical system 40 is not limited to a specific number and is determined appropriately taking into consideration the beam diameter required for the image light LB. The pickup optical system 40 expands the beam diameter of the blue laser light B diffused by the diffusion element 30 and emits it to the +X side along the X direction.

[0029] The despeckle element 201 is disposed at a predetermined distance in the X direction from the pickup optical system 40 and on the +X side of the second lens 42 of the pickup optical system 40. The first lens array 50 is adjacent to the +X side of the despeckle element 201. The despeckle element 201 is composed of a metasurface element 211. The metasurface element 211 will be described later.

[0030] The first lens array 50 has a plurality of microlenses 51 for splitting the blue laser light DB emitted from the despeckle element 201 into a plurality of partial beams in the YZ plane. The plurality of microlenses 51 are arranged in the Y direction and the Z direction in the YZ plane. The first lens array 50 outputs the blue laser light DB split into a plurality of partial beams toward the +X side along the X direction.

[0031] The second lens array 60 has a plurality of microlenses 61 arranged corresponding to the plurality of microlenses 51 of the first lens array 50. The second lens array 60, together with the superimposing lenses 81 and 82, forms an image of each microlens 61 of the second lens array 60 in the vicinity of the image forming area of ​​the light modulation element 95B. The plurality of microlenses 61 are arranged in a matrix on the YZ plane perpendicular to the optical axis AX1. The second lens array 60 emits the blue laser light DB, which has been split into a plurality of partial beams, toward the +X side along the X direction.

[0032] The polarization conversion element 70 converts each partial light beam split by the first lens array 50 into a predetermined linearly polarized light beam according to the characteristics of the light modulation element 95B. The polarization conversion element 70 has a polarization separation layer, a reflective layer, and a retardation plate. The polarization separation layer of the polarization conversion element 70 transmits one linearly polarized component of the polarization components contained in the blue laser light DB incident from the second lens array 60 and reflects the other linearly polarized component parallel to the YZ plane perpendicular to the optical axis AX1. The reflective layer of the polarization conversion element 70 reflects the other linearly polarized component reflected by the polarization separation layer in the X direction parallel to the optical axis AX1. The retardation plate of the polarization conversion element 70 converts the other linearly polarized component reflected by the reflective layer into one linearly polarized component and emits the converted one linearly polarized component toward the +X side along the X direction.

[0033] The superimposing lens 81 is disposed at a predetermined distance from the polarization conversion element 70 in the X direction and on the +X side of the polarization conversion element 70. The superimposing lens 82 is disposed at a predetermined distance from the superimposing lens 81 in the X direction and on the +X side of the superimposing lens 81. The superimposing lenses 81 and 82 collect the partial light beams of one of the linearly polarized components emitted from the polarization conversion element 70 and superimpose them near the image forming area of ​​the light modulation element 95B. The first lens array 50, the second lens array 60, and the superimposing lenses 81 and 82 constitute an integrator optical system that uniforms the in-plane light intensity distribution of the blue laser light B or light LL in the image forming area of ​​the projector 100.

[0034] Field lens 90B is disposed a predetermined distance in the X direction from superimposing lens 82 and on the +X side of superimposing lens 82. Field lens 90B aligns the traveling direction of the outer periphery of blue laser light DB emitted from superimposing lens 82 in the YZ plane, and emits the aligned blue laser light DB to the +X side along the X direction. Field lens 90B suppresses attenuation and reduction in clarity of the incident blue laser light DB.

[0035] Light modulation element 95B is disposed at a predetermined distance from field lens 90B in the X direction and on the +X side of field lens 90B. Light modulation element 95B is configured, for example, by a liquid crystal light valve. The liquid crystal light valve includes a liquid crystal layer and an energy transfer layer. The liquid crystal layer is made of, for example, nematic liquid crystal or smectic liquid crystal. The energy transfer layer is configured by a photoconductor or a light absorbing film. The type of energy transfer layer is selected depending on the writing method using blue laser light DB. Light modulation element 95B modulates blue laser light DB incident from field lens 90B in accordance with image information to form blue image light LB, and emits the image light LB to the +X side along the X direction.

[0036] The image light LB emitted from the light modulation element 95B enters the cross dichroic prism 3 from the side surface 3b in the projector 100 shown in FIG.

[0037] 1 and 2, on the optical path of blue image light LB from projector 100, the position where screen SCR is disposed, where an image is formed when light LL is projected, and position PS4 of the image forming area of ​​light modulation element 95B are conjugate to each other. Also, as shown in FIG. 2, in third light source module 1B, position PS4 of the image forming area of ​​light modulation element 95B and position PS3 where first lens array 50 and despeckle element 201 are disposed are conjugate to each other. Therefore, by despeckling blue laser light B at position PS3, the effect of this despeckle is highly apparent in blue laser light DB incident on light modulation element 95B at position PS4. Furthermore, because image light LB is formed by blue laser light DB that has already been despeckled at position PS4, the despeckle countermeasures are effectively implemented for light LL projected onto screen SCR, as described with reference to FIG. 1.

[0038] 1 includes an LD light source (not shown) that emits red laser light, instead of the LD light source 12 that emits blue laser light B of the third light source module 1B. The first light source module 1R includes the same components as the third light source module 1B, except for the LD light source 12. However, in the first light source module 1R, the red laser light is emitted from the LD light source toward the −X side along the X direction. In the first light source module 1R, a light source unit having an LD light source that emits red laser light, a condenser lens for the red laser light, a diffusion element, a pickup optical system, a despeckle element, a first lens array, a second lens array, a polarization conversion element, a superimposing lens, a field lens, and an optical modulation element are sequentially arranged along the X direction from the +X side to the −X side, while maintaining the relative positional relationship between the corresponding components in the third light source module 1B.

[0039] The second light source module 1G shown in FIG. 1 includes an LD light source (not shown) that emits green laser light, instead of the LD light source 12 that emits green laser light B in the third light source module 1B. The second light source module 1G includes the same components as the third light source module 1B, except for the LD light source 12. However, in the second light source module 1G, the green laser light is emitted from the LD light source toward the +Z side along the Z direction. In the second light source module 1G, a light source unit having an LD light source that emits green laser light, a condenser lens for the green laser light, a diffusion element, a pickup optical system, a despeckle element, a first lens array, a second lens array, a polarization conversion element, a superimposing lens, a field lens, and an optical modulation element are sequentially arranged from the -Z side to the +Z side along the Z direction, while maintaining the relative positional relationship between the corresponding components in the third light source module 1B.

[0040] (Despeckle element) 3A is a side view of the metasurface element 211 of the first embodiment as viewed from the Y direction. FIG. 3B is a plan view of the metasurface element 211 as viewed from the X direction. As shown in FIGS. 3A and 3B, the metasurface element 211 includes a substrate (base material) 202 and a plurality of microstructures 204.

[0041] The substrate 202 may have a disk shape or the like to match the beam shape of the blue laser light B incident from the pickup optical system 40. The substrate 202 has a plate surface 202a on the -X side, i.e., the incident side of the blue laser light B, and a plate surface 202b on the +X side, i.e., the exit side of the blue laser light B. The size of the substrate 202 in the YZ plane is at least larger than the beam diameter of the blue laser light B at a position a predetermined distance away from the pickup optical system 40 on the +X side, and preferably slightly larger than the beam diameter of the blue laser light B. The substrate 202 is formed of a material that transmits at least the blue laser light B and has no absorption characteristics for the blue laser light B or has extremely low absorption characteristics for the blue laser light B. The material of the substrate 202 is, for example, the same as the material of the microstructure 204 described below, but may also be, for example, quartz, optical glass, or the like.

[0042] The microstructures 204 are provided on a plate surface (first reference plane) 202a of the substrate 202. The microstructures 204 have a width d in a direction parallel to the plate surface 202a and a height t1 in an X direction (a direction intersecting the reference plane) perpendicular to the plate surface 202a. The metasurface element 211 has a plurality of microstructures 204. The widths d and heights t1 of the plurality of microstructures 204 and the spacing p between the microstructures 204 may be equal to or different from each other, and are set randomly as described below.

[0043] If at least one microstructure 204 is arranged on the metasurface element 211, a resonance phenomenon of the blue laser light B in the microstructure 204 may occur. Therefore, the total number of microstructures 204 provided on the metasurface element 211 is determined based on the amount of despeckle and the amount of phase modulation φ required for the blue laser light B. B It is determined appropriately according to the width d and height t1 of the microstructure 204, taking into consideration the above, and the spacing p between the microstructures 204. Note that in each of the figures showing the schematic configuration of the metasurface element from Figure 3A onwards, only a portion of the multiple microstructures arranged on the substrate 202 is illustrated in an appropriately enlarged state.

[0044] As shown in FIG. 2, the metasurface element 211 randomly modulates the phase of the blue laser light B emitted from the LD light source 12 and expanded by the pickup optical system 40 for each position within the area of ​​the metasurface element 211 in the YZ plane. The area of ​​the metasurface element 211 in the YZ plane refers to the area S1 shown in FIGS. 3A and 3B. As a result, the despeckle element 201 formed by the metasurface element 211 randomly modulates the phase of the incident blue laser light B and emits the phase-modulated blue laser light DB to the first lens array 50. In other words, the metasurface element 211 functions as a random phase modulation element.

[0045] The width d and height t1 of the microstructure 204 of the metasurface element 211 shown in FIGS. 3A and 3B, and the interval p between the microstructures 204, are determined by the width d and the phase modulation amount φ when the height t1 of one microstructure 204 is set to a predetermined value according to the peak wavelength of the blue laser light B, for example. B The height t1 of the microstructure 204 is set based on the relationship between the phase modulation amount φ of the blue laser light B and the phase modulation amount φ of the blue laser light B. B In the metasurface element 211, the phase modulation amount φ of the blue laser light B in the region S1 where the plurality of microstructures 204 are arranged is B The range of is set to 0 to 2π. That is, in the metasurface element 211, the height t1 of the plurality of microstructures 204 is a predetermined value determined based on the peak wavelength of the blue laser light B, and the phase modulation amount φ B is set to a predetermined value that can be up to 2π. The predetermined value of the height t1 is about several hundred nm, for example, 500 nm or less, and preferably 200 nm or less. It is preferable that the predetermined value of the height t1 is set in consideration of the dimensions that can be produced and processed with high precision and low yield using the material of the microstructure 204 in the device used to manufacture the metasurface element 211, without excessively exceeding those dimensions.

[0046] The phase modulation amount φ of the blue laser light B transmitted through the microstructure 204 when the width d is changed under the condition that the height t1 of the plurality of microstructures 204 is the above-mentioned predetermined value. B is calculated by numerical calculation. Specifically, when the width d increases from 0, the phase modulation amount φ B increases nonlinearly and continuously from 0 to near 2π. B When the width d increases further after reaching the vicinity of 2π, the phase modulation amount φ B first suddenly decreases discontinuously to the vicinity of 0, then increases nonlinearly and continuously from the vicinity of 0 to the vicinity of 2π again, repeating the aforementioned sudden discontinuous decrease and continuous increase.

[0047] In the metasurface element 211, the width d of each microstructure 204 is the phase modulation amount φ Bare at least different from each other, and the phase modulation amounts φ between the adjacent microstructures 204 are B The difference between these is set to vary randomly within the region S1.

[0048] The spacing p between the microstructures 204 is appropriately set so that when three microstructures 204 are extracted, for example, two microstructures 204 that are adjacent to each other in the region S1 and another microstructure 204 that is closest to one of these two microstructures 204 and different from the other microstructure 204, the spacing between the centers or the centers of gravity of these microstructures 204 in the YZ plane is different from each other. By setting it in this way, highly random phase modulation is performed on the blue laser light B that is incident on the region S1 of the metasurface element 211.

[0049] By adjusting the width d of each of the plurality of microscopic structures 204 and the interval p between the microscopic structures 204, the randomness and degree of randomness of the phase modulation by the plurality of microscopic structures 204 can be adjusted freely and with high precision.

[0050] The blue laser light B incident on the metasurface element 211 from the -X side is confined in each of the microstructures 204, which have the width d and height t1 set as described above, and resonates due to the optical confinement. The blue laser light DB emitted from the multiple microstructures 204 has a random phase modulation amount φ within the region S1. B occurs.

[0051] The material of the microstructure 204 preferably has a high refractive index at least for the blue laser light B and has little absorption. When the material of the microstructure 204 has a high refractive index for the blue laser light B, the phase modulation amount φ that can be obtained for a certain height t1 is B This increases the degree of freedom in designing the microstructure 204. As the material for the microstructure 204, titanium oxide (TiO2), silicon nitride (SiN), etc., which have a higher refractive index than, for example, quartz or optical glass, etc., and have low absorption of light in the visible wavelength range, are preferable.

[0052] As described above, the behavior when blue laser light B is incident on metasurface element 211, in which width d and height t1 of microstructure 204 and spacing p between microstructures 204 are set, is determined using electromagnetic wave analysis such as finite difference time domain method (FDTD method) because the dimensions of microstructure 204 are equal to or less than the peak wavelength of blue laser light B. In other words, electromagnetic wave analysis such as FDTD method is used for design evaluation of metasurface element 211.

[0053] The metasurface element 211 is fabricated by a method such as reactive ion etching (RIE), focused ion beam (FIB), or nanoimprint lithography.

[0054] It is preferable that the +X side end face of the despeckle element 201 made up of the metasurface element 211, i.e., the plate surface 202b of the substrate 202 of the metasurface element 211, abuts against the -X side surface of the first lens array 50 shown in Fig. 2. Note that the plate surface 202b of the substrate 202 may be arranged with a slight gap in the X direction from the -X side surface of the first lens array 50. A slight gap means a gap so short that it can be considered that the +X side end face of the despeckle element 201 and the -X side surface of the first lens array 50 are both arranged at position PS3, which will be described later, in the X direction.

[0055] The third light source module 1B of the first embodiment described above includes an LD light source 12, a metasurface element 211, and an optical modulation element 95B. The LD light source 12 emits blue laser light B. The metasurface element 211 constitutes a despeckle element 201 that takes measures to despeckle the blue laser light B, and modulates the phase of the blue laser light B emitted from the LD light source 12. The optical modulation element 95B modulates the blue laser light DB that has been emitted from the metasurface element 211 and has had its phase modulated, to generate image light LB.

[0056] In the third light source module 1B of the first embodiment, the despeckle element 201 is composed of a metasurface element 211, and therefore the despeckle element 201 can be configured to be ultra-thin and small compared to conventional elements used to counter despeckle, such as diffusers.

[0057] In the third light source module 1B of the first embodiment, the metasurface element 211 is disposed at a position PS3 conjugate with the image forming area of ​​the light modulation element 95B. A position PS4 in the X direction of the image forming area of ​​the light modulation element 95B is a position conjugate with the screen SCR on the optical path of the light LL formed by combining the blue image light LB and the three color image lights LR, LG, and LB.

[0058] According to the third light source module 1B of the first embodiment, the despeckle element 201 composed of the metasurface element 211 is placed at position PS3, and the blue laser light B is despeckled at position PS3, so that the despeckle effect of the blue laser light DB in the image forming area of ​​the light modulation element 95B can be maximized compared to when the despeckle element 201 is placed at a position that is not conjugate with position PS3 in the X direction.

[0059] In the third light source module 1B of the first embodiment, the metasurface element 211 includes a substrate 202 and at least one microstructure 204. The substrate 202 has a plate surface 202a on the -X side as a reference for placing the metasurface element 211 in the X direction. The microstructure 204 is disposed on the plate surface 202a of the substrate 202. The microstructure 204 has a width (predetermined width) d in the Z direction parallel to the plate surface 202a, and a height (predetermined height) t1 in the X direction perpendicular to the plate surface 202a. The height t1 of the multiple microstructures 204 is set to a predetermined height t1 according to the peak wavelength of the blue laser light B. The width d of the multiple microstructures 204 is determined by a phase modulation amount φ required for the blue laser light DB that is incident on the microstructure 204, undergoes an optical confinement effect, resonates, and then is emitted from the microstructure 204. BThe term "laser light passing through the microstructure" as used in this specification and claims refers to blue laser light DB that is incident on the microstructure 204, undergoes the light confinement effect, resonates, and is then emitted from the microstructure 204, as described above.

[0060] According to the third light source module 1B of the first embodiment, the width d and height t1 of the microstructure 204 are set to dimensions on the same order as the peak wavelength or wavelength band of the blue laser light B, so that the metasurface element 211 and the despeckle element 201 can be configured to be ultra-thin and small.

[0061] In the third light source module 1B of the first embodiment, at least one of the height t1 and the width d of the microstructure 204 of the metasurface element 211 is determined by the phase modulation amount φ of the blue laser light B passing through the microstructure 204. B It is set according to the

[0062] The blue laser light B incident on the metasurface element 211 is confined in the microstructure 204, and causes a resonance called Fabry-Perot resonance in the X direction. According to the third light source module 1B of the first embodiment, the resonance condition of the blue laser light B is changed by adjusting the width d and height t1 of the microstructure 204, and the phase modulation amount φ of the blue laser light B is adjusted. B In addition, when the metasurface element 211 has a plurality of microstructures 204 in the region S1, the phase modulation amount φ can be adjusted with high precision and freely by adjusting the width d and height t1 of the microstructures 204 in part or in part, and the interval p between the microstructures 204 in part or in part, so that the phase modulation amount φ can be adjusted to be different from the surroundings of the part or in part in the region S1. B can be expressed.

[0063] In the metasurface element 211, at least one of the height t1 and the width d of the microstructure 204 is determined by the phase modulation amount φ of the blue laser light B passing through the microstructure 204. BThat is, in the modification of the first embodiment described above, the height t1 of the plurality of microstructures 204 is set in accordance with the phase modulation amount φ required for the blue laser light DB passing through the microstructures 204. B The width d of the plurality of microstructures 204 is set to a predetermined width in accordance with the peak wavelength of the blue laser light B. Furthermore, both the height t1 and the width d of the plurality of microstructures 204 may be set for each microstructure 204 in accordance with the peak wavelength of the blue laser light B and the phase modulation amount φ B It may be set according to the

[0064] In the third light source module 1B of the first embodiment, the metasurface element 211 includes a plurality of microstructures 204. Even when one microstructure 204 is provided on the substrate 202, the optical confinement effect and Fabry-Perot resonance of the blue laser light B occur as described above. However, when a plurality of microstructures 204 are provided on the substrate 202, the Fabry-Perot resonance in each microstructure 204 is coupled with the resonance between the plurality of microstructures 204 in a direction parallel to the YZ plane, resulting in a plurality of resonance effects including guided mode resonance. Therefore, the phase modulation amount φ of the blue laser light B can be adjusted by adjusting the width d and height t1 of each microstructure 204. B By easily and freely controlling the width d, height t1, and spacing p of the plurality of microstructures 204, and adjusting the relative arrangement of the plurality of microstructures 204, the conditions for the waveguide mode resonance of the blue laser light B can be controlled, and a metasurface element 211 that exhibits a desired phase modulation function regardless of continuity or regularity in the YZ plane can be obtained. Furthermore, even in a situation where the installation space in the projector 100 is limited, by adjusting the width d, height t1, and spacing p of some or local microstructures 204 among the plurality of microstructures 204, the phase modulation amount φ in the region S1 can be adjusted in accordance with, for example, the light intensity distribution in the YZ plane of the blue laser light B, the arrangement of each component of the third light source module 1B, the optical path of the blue laser light B, etc. B The distribution of can be freely set.

[0065] In the third light source module 1B of the first embodiment, in the region S1 covering the entire plate surface 202a of the substrate 202 of the metasurface element 211, the height t1 of the microstructure 204 is set so that the phase modulation amount of the blue laser light B emitted from the microstructure 204 is 0 to 2π.

[0066] According to the third light source module 1B of the first embodiment, the phase modulation amount φ of the blue laser light B is 2π or more. B is the phase modulation amount φ between 0 and 2π B Considering that the phase is the same as that of the metasurface element 211, the minimum required phase modulation amount φ B By setting the height t1 of the microstructure 204, it is possible to suppress the height t1 of the microstructure 204 of the metasurface element 211. The higher the height t1 of the microstructure 204, the more likely it is that variations and errors will occur in the columnar or tapered shape and height of the microstructure 204, making it more difficult to manufacture the metasurface element 211 in the shape as designed. By appropriately suppressing the height t1 of the microstructure 204 as described above, the degree of freedom in designing the metasurface element 211 and the despeckle element 201 is increased, the manufacturing of the metasurface element 211 is made easier, errors during manufacturing are reduced, and further thinning and miniaturization can be achieved.

[0067] The projector 100 of the first embodiment includes the above-described third light source module 1B and a projection optical system 4. The projection optical system 4 combines the image light LR, LG, and LB from the third light source module 1B, and then expands the combined light LL toward the +Z side along the Z direction and projects it onto a screen SCR arranged at a predetermined position in the Z direction.

[0068] According to the projector 100 of the first embodiment, an ultra-thin and small despeckle element 201 made up of a metasurface element 211 is disposed in the third light source module 1B, which makes it possible to effectively prevent despeckle from occurring for the light LL projected onto the screen SCR while preventing the third light source module 1B from becoming larger. In particular, when the projector 100 is made smaller and lighter, the space available for disposing a despeckle element is extremely limited in the third light source module 1B and in each of the second light source modules 1G and 1R that have the same components as the third light source module 1B. Even in such cases, the despeckle element 201 made up of the metasurface element 211 can be easily disposed in the position PS3 where the despeckle effect of each of the third light source modules 1B, 1G, and 1R is maximized, or in other desired positions.

[0069] <First Modification> Next, a first modified example of the metasurface element 211 of the first embodiment will be described using Figures 4A and 4B. In the metasurface elements of each modified example below, components that are common to the metasurface element of the corresponding embodiment will be given the same reference numerals as the common components, and their description will be omitted.

[0070] Fig. 4A is a side view of a metasurface element 212 of a first modified example of the metasurface element 211 of the first embodiment, as viewed from the Y direction. Fig. 4B is a plan view of the metasurface element 212, as viewed from the X direction.

[0071] As shown in Figures 4A and 4B, the metasurface element 212 includes the substrate (base material) 202 described in the first embodiment and a plurality of microstructures 204. However, the metasurface element 212 is partitioned into a plurality of regions in the radial direction from the center of the plate surface 202a, i.e., the center of the substrate 202 as viewed from the X direction. The metasurface element 212 shown in Figures 4A and 4B is partitioned into three regions S1, S2, and S3 in the radial direction from the center of the plate surface 202a. A plurality of microstructures 204 are formed in each of the plurality of regions S1, S2, and S3.

[0072] The phase modulation amount φ of the blue laser light B passing through the area S1 including the center of the plate surface 202a B The range of is set to 0 to 2π. That is, the height t1 of the plurality of microstructures 204 arranged in the region S1 is a predetermined value determined based on the peak wavelength of the blue laser light B, and the phase modulation amount φ B are set to a predetermined value that can be up to 2π.

[0073] The region S2 is adjacent to the region S1 in the radial direction and is located radially outward of the region S1. The phase modulation amount φ of the blue laser light B passing through the region S2 B The range of is set to 0 to π. In the metasurface element 212, the height t2 of the plurality of microstructures 204 arranged in the region S2 is set to be equal to the height t1. The width d of the plurality of microstructures 204 arranged in the region S2 is set to be equal to the phase modulation amount φ of the blue laser light B passing through the region S2. B is appropriately adjusted so that it is at most π.

[0074] The region S3 is adjacent to the region S2 in the radial direction and is located radially outward of the region S2. The phase modulation amount φ of the blue laser light B passing through the region S3 B The range of is set to 0 to (π / 2). In the metasurface element 212, the height t3 of the plurality of microstructures 204 arranged in the region S3 is set to be equal to the height t1. The width d of the plurality of microstructures 204 arranged in the region S3 is set to be equal to the phase modulation amount φ of the blue laser light B passing through the region S2. B is adjusted appropriately so that it is at most (π / 2).

[0075] As described above, the metasurface element 212 of the first modified example of the first embodiment includes the substrate 202 and at least one microstructure 204. In the metasurface element 212 of the first modified example, at least one of the heights t1 to t3 and the width d of the multiple microstructures 204 is determined based on the phase modulation amount φ of the blue laser light B passing through the microstructure 204. BThe metasurface element 212 of the first modified example is configured, like the metasurface element 211, with the substrate 202 and the microstructure 204 having dimensions approximately the same as the wavelength band of the blue laser light B, so that an ultra-thin and small despeckle element 201 can be realized. Also, with the metasurface element 212 of the first modified example, the phase modulation amount φ of the blue laser light B can be adjusted by adjusting the width d and height t1 of the microstructure 204. B can be adjusted freely and precisely.

[0076] The metasurface element 212 of the first modified example of the first embodiment is partitioned into a plurality of regions S1, S2, and S3 along the radial direction of the plate surface 202a of the substrate 202. Of the two regions S1 and S2 adjacent to each other in the radial direction of the plate surface 202a, the maximum phase modulation amount of blue laser light B passing through the microstructures 204 arranged on the plate surface 202a of the region (first region) S2 on the outer radial side is π, which is smaller than the maximum phase modulation amount 2π of blue laser light B passing through the microstructures 204 arranged on the plate surface 202a of the region (second region) S1 (the radially inner one of the two regions) Of the two regions S2 and S3 adjacent to each other in the radial direction of the plate surface 202a, the maximum phase modulation amount of blue laser light B passing through the microstructures 204 arranged on the plate surface 202a in the radially outer region (first region) S3 is (π / 2), which is smaller than the maximum phase modulation amount π of blue laser light B passing through the microstructures 204 arranged on the plate surface 202a in region S1 (the radially inner second region of the two regions). That is, the phase modulation amount of blue laser light B passing through the region S1 closest to the center of the plate surface 202a is 0 to 2π. The phase modulation amount of blue laser light B passing through region S2, which is outer than region S1, is 0 to π. The phase modulation amount of blue laser light B passing through region S3, which is outer than region S2, is 0 to (π / 2).

[0077] In the metasurface element 212 of the first modification, the maximum phase modulation amount of the blue laser light B passing through the region decreases as it progresses toward the outermost region in the radial direction of the plate surface 202a of the substrate 202, and therefore the divergence angle in the YZ plane of the blue laser light DB emitted to the +X side from the microstructures 204 in the region decreases. According to the metasurface element 212 of the first modification, the divergence angle of the blue laser light DB emitted to the +X side by the multiple microstructures 204 in the outermost region of the plate surface 202a can be made smaller than that of the innermost region of the plate surface 202a in the radial direction. This reduces the amount of blue laser light DB leaking outside the metasurface element 212 in the YZ plane, i.e., outside the region to be processed in the third light source module 1B, and improves the utilization efficiency of the blue laser light DB.

[0078] In the metasurface element 212 of the first modification, the width d of the multiple microstructures 204 formed in each of the regions S1, S2, and S3 is adjusted to make the maximum phase modulation amount for the blue laser light B different in each of the regions S1, S2, and S3. However, it is sufficient to adjust at least one of the heights t1 to t3 and the width d. That is, the maximum phase modulation amount for the blue laser light B passing through each of the regions S1, S2, and S3 may be sequentially reduced by adjusting the heights t1, t2, and t3 of the multiple microstructures 204 formed in each of the regions S1, S2, and S3 of the metasurface element 212. Furthermore, the maximum phase modulation amount for the blue laser light B passing through each of the regions S1, S2, and S3 may be sequentially reduced by adjusting both the heights t1, t2, and t3 and the width d of the multiple microstructures 204 formed in each of the regions S1, S2, and S3 of the metasurface element 212. Whether to adjust either or both of the heights t1, t2, t3 and width d of the microstructures 204 in each region partitioned in a planar view in the metasurface element 212 is selected appropriately taking into consideration the minimum dimensions that can achieve the desired dimensions with high precision and good yield in the manufacturing method and manufacturing equipment for the metasurface element 212.

[0079] Furthermore, in the metasurface element 212 of the first modified example, the plate surface 202a of the substrate 202 is divided into three regions S1 to S3 along the radial direction, but the number of divided regions is not limited to three. That is, in the metasurface element 212 of the first modified example, it is sufficient that the maximum phase modulation amount imparted to the blue laser light B passing through the outer radial region is smaller than the maximum phase modulation amount imparted to the blue laser light B passing through the adjacent inner region, and the number of divided regions may be two, four or more.

[0080] Furthermore, as a further modification of the metasurface element 212 of the first modification, the maximum phase modulation amount of the blue laser light DB emitted from the microstructure 204 may be reduced as one moves from the center or a predetermined position in the radial direction of the plate surface 202a of the substrate 202 toward the outer edge. Even with this configuration, it is possible to reduce the blue laser light DB leaking outside the processing target area in the third light source module 1B, thereby increasing the utilization efficiency of the blue laser light DB.

[0081] Furthermore, in the metasurface element 212 of the first modified example, the maximum phase modulation amounts imparted to the blue laser light B passing through the three regions S1 to S3 are 2π, π, and (π / 2), but may also be, for example, 2π, (4π / 3), (2π / 3), or π, (π / 2), (π / 4), etc. In other words, in the metasurface element 212 of the first modified example, it is sufficient to maintain the magnitude relationship that the maximum phase modulation amount imparted to the blue laser light B passing through the outer radial region is smaller than the maximum phase modulation amount imparted to the blue laser light B passing through the adjacent inner region, as described above, and the maximum phase modulation amount in each region can be adjusted as appropriate.

[0082] In the metasurface element 212 of the first modification, the ratio of the diameters of the multiple regions partitioned along the radial direction of the plate surface 202a of the substrate 202 is appropriately adjusted taking into consideration the amount by which the divergence angle of the blue laser light DB emitted from the microstructures 204 in each region should be reduced and the size of the substrate 202 in the YZ plane, i.e., the diameter of the substrate 202, etc. In order to improve the despeckle performance of the metasurface element 212 while increasing the utilization efficiency of the blue laser light DB, it is preferable that the maximum phase modulation amount imparted to the blue laser light B emitted from the inner region in the radial direction is larger, and it is preferable that the region to which this relatively larger maximum phase modulation amount is imparted is wider than that of the outer region in the radial direction. As an example, in the metasurface element 212 of the first modification described above, the range of region S1 is set to be 50% to 70% of the diameter from the center of the plate surface 202a, and the range of region S2 is set to be 80% to 90% of the diameter of the plate surface 202a from the outer edge of region S1.

[0083] <Second Modification> Next, a second modified example of the metasurface element 211 of the first embodiment will be described with reference to FIG.

[0084] Figure 5 is a side view of a metasurface element 213, a second modified example of the metasurface element 211 of the first embodiment, as viewed from the Y direction. As shown in Figure 5, the metasurface element 213 comprises the substrate (base material) 202 described in the first embodiment and a plurality of microstructures 204. However, in the metasurface element 213, an oscillator 402 is provided at a radially outer position of the plate surface 202b. When the oscillator 402 is activated, the metasurface element 213 vibrates linearly along a direction parallel to the YZ plane, and barely vibrates in the X direction.

[0085] The oscillator 402 is configured by, for example, a micromotor, a MEMS (Micro Electro Mechanical Systems), a piezoelectric element, etc. The type of oscillator 402 is not particularly limited as long as it can vibrate the metasurface element 213 in a direction parallel to the YZ plane as described above.

[0086] As described above, the metasurface element 213 of the second modified example of the first embodiment includes the substrate 202 and at least one microstructure 204. In the metasurface element 213 of the second modified example, at least one of the height t1 and the width d of the plurality of microstructures 204 is determined based on the phase modulation amount φ of the blue laser light B passing through the microstructure 204. B The metasurface element 213 of the second modified example is configured, like the metasurface element 211, with the substrate 202 and the microstructure 204 having dimensions approximately the same as the wavelength band of the blue laser light B, so that an ultra-thin and small despeckle element 201 can be realized. Also, with the metasurface element 213 of the second modified example, the phase modulation amount φ of the blue laser light B can be adjusted by adjusting the width d and height t1 of the microstructure 204. B can be adjusted freely and precisely.

[0087] The metasurface element 213 of the second modification of the first embodiment further includes an oscillator 402 that vibrates the substrate 202 and the plurality of microstructures 204, which are integrally formed with each other, in a direction parallel to the plate surface (first reference plane) 202a, i.e., a direction parallel to the YZ plane. In the metasurface element 213 of the second modification of the first embodiment, the oscillator 402 is activated to change the position of the microstructures 204 in the YZ plane, thereby causing a temporal change in the phase modulation pattern for the incident blue laser light B. This causes a temporal change in the spatial distribution of the phase modulation formed by the microstructures 204, and speckle noise in the blue laser light DB is superimposed on it over time. According to the metasurface element 213 of the second modification, the oscillator 402 is used to temporally change the phase modulation pattern for the blue laser light B, thereby enhancing the despeckle effect for the blue laser light DB compared to the metasurface element 211 of the first embodiment.

[0088] The shape of the oscillator 402 and its arrangement on the metasurface element 213 can be changed as appropriate as long as they do not interfere with the blue laser light B and DB traveling along the X direction. For example, if the oscillator 402 is made of a material that transmits the blue laser light B and DB, the oscillator 402 may be arranged near the center of the plate surface 202b in the radial direction.

[0089] Furthermore, as a further modification of the metasurface element 213 of the second modification, the metasurface element 213 may be rotatable around the center of the plate surfaces 202a and 202b in a direction parallel to the YZ plane. When the oscillator 402, which is a rotary motor or the like, is made of a material that transmits the blue laser light B and DB, and the substrate 202 is slightly larger than the beam diameter of the incident blue laser light B as described in the first embodiment, the oscillator 402 may be disposed at the center of the plate surface 202b of the substrate 202. When the oscillator 402, which is a rotary motor or the like, is made of a material that does not easily transmit the blue laser light B and DB, for example, the radius of the substrate 202 may be expanded to approximately the beam diameter of the incident blue laser light B, and the oscillator 402 may be disposed at the center of the plate surfaces 202a and 202b, and the oscillator 402 may be disposed on the ±Y side and the ±Z side of the optical axis AX1 of the blue laser light B and DB. Blue laser light B is incident from the -X side on a region of metasurface element 213 that rotates parallel to the YZ plane around oscillator 402, overlapping with the optical path of blue laser light B. By using such a rotationally vibrating metasurface element 213, the phase modulation pattern for blue laser light B can be changed over time, similar to the linearly vibrating metasurface element 213 described above in the second modified example, thereby enhancing the despeckle effect of blue laser light DB compared to metasurface element 211 of the first embodiment. Note that, as long as the spatial distribution of the phase modulation formed by the multiple microstructures 204 can be changed over time as described above, the vibration direction and vibration pattern can be selected arbitrarily.

[0090] In addition, in the metasurface element 213 of the second modified example, as in the first modified example, when viewed from the X direction, it may be divided into multiple regions in the radial direction, and the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer.

[0091] <Third Modification> Next, a third modified example of the metasurface element 211 of the first embodiment will be described with reference to FIG.

[0092] Figure 6 is a side view of a metasurface element 214 of a third modified example of the metasurface element 211 of the first embodiment, viewed from the Y direction. As shown in Figure 6, the metasurface element 214 comprises the substrate (base material) 202 described in the first embodiment and a plurality of microstructures 204. However, in the metasurface element 214, a heater 404 is provided at a radially outer position of the plate surface 202b.

[0093] The multiple microstructures 204 of the metasurface element 214 are formed of a material that transmits blue laser light B and changes volume by shrinking or expanding with temperature, or a material that changes phase between an amorphous and crystalline state. Examples of materials that shrink or expand with temperature include optical resins with high thermal expansion, such as polymethyl methacrylate (PMMA). Examples of materials for the microstructures 204 that change phase with temperature include chalcogenide-based germanium (Ge)-antimony (Sb)-tellurium (Te) photonic phase transition material (GST) with selenium (Se) added (GSST). When GSST is heated, its atomic structure changes from amorphous to randomly entangled atoms, shifting to a more ordered crystalline structure than before heating, resulting in a phase change. The phase change of GSST changes the optical path of the blue laser light B passing through the microstructures 204, affecting the refractive power of the GSST. On the other hand, the phase change of the GSST has only a small effect on the transparency of the microstructure 204 to the blue laser light B. The volume change or phase change of the microstructure 204 is reversible with respect to a change in temperature.

[0094] The substrate 202 is formed of a material that transmits the blue laser light B and has thermal conductivity that allows at least the heat from the heater 404 to be transferred to the plurality of microstructures 204. The material of the substrate 202 may be the same material as the microstructures 204 that transmit the blue laser light B and that contracts or expands with a change in temperature or that changes phase with a change in temperature.

[0095] In the metasurface element 214, the heater 404 is operated, and the temperature of at least a plurality of microstructures 204 changes within a range in which the material of the microstructures 204 can contract or expand, whereby the size of each microstructure 204, i.e., the width d, height t1, and spacing p between the microstructures 204, change according to the temperature, and the phase modulation amount φ for the blue laser light B is B Alternatively, the heater 404 is operated to change the temperature of at least the plurality of microstructures 204 within a range where a phase change between an amorphous state and a crystalline state is possible, thereby changing the refractive power of each microstructure 204 and the phase modulation amount φ B changes.

[0096] As described above, the metasurface element 214 of the third modified example of the first embodiment includes the substrate 202 and at least one microstructure 204. In the metasurface element 214 of the third modified example, at least one of the height t1 and the width d of the plurality of microstructures 204 is set to an initially set phase modulation amount φ B The metasurface element 214 of the third modified example is configured, like the metasurface element 211, with the substrate 202 and the microstructure 204 having dimensions approximately the same as the wavelength band of the blue laser light B, so that an ultra-thin and small despeckle element 201 can be realized.

[0097] In the metasurface element 214 of the third modified example of the first embodiment, the microstructure 204 is made of a material that contracts or expands with temperature changes. In the metasurface element 214 configured in this manner, the width d and height t1 of the microstructure 204 change when the heater 404 is turned on or off, so that the phase modulation pattern for the incident blue laser light B can be changed over time.

[0098] Furthermore, in the metasurface element 214 of the third modified example of the first embodiment, the microstructure 204 may be made of a material that changes phase between an amorphous state and a crystalline state depending on the temperature. In the metasurface element 214 configured in this manner, when the heater 404 is turned on or off, the microstructure 204 changes phase between an amorphous state and a crystalline state, and the refractive power of the microstructure 204 changes, so that the phase modulation pattern for the incident blue laser light B can be changed over time.

[0099] In the metasurface element 214 of the third modified example of the first embodiment, the spatial distribution of the phase modulation formed by the microstructure 204 changes over time as described above, and speckle noise in the blue laser light DB is superimposed over time. According to the metasurface element 214 of the third modified example, the temperature control using the heater 404 controls the phase modulation amount φ of the blue laser light B passing through the microstructure 204. B is changed over time, and the phase modulation pattern of the multiple microstructures 204 for the blue laser light B is changed over time, thereby increasing the randomness of the phase modulation pattern for the blue laser light B and the despeckle effect in the blue laser light DB compared to the metasurface element 211 of the first embodiment.

[0100] In addition, in the metasurface element 214 of the third modified example, as in the first modified example, when viewed from the X direction, it may be divided into multiple regions in the radial direction, and the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer.

[0101] Furthermore, the metasurface element 214 of the third variant may further include an oscillator 402 that vibrates the substrate 202 and the multiple microstructures 204, which are integrally formed with each other, in a direction parallel to the YZ plane, as in the second variant.

[0102] In the metasurface element 211 of the first embodiment and the metasurface elements 212, 213, and 214 of the first to third modified examples of the first embodiment, the microstructure 204 is provided only on the plate surface 202a of the substrate 202, but the microstructure 204 may be provided on either the plate surface 202a or 202b of the substrate 202, and may be provided, for example, only on the plate surface 202b. In that case, the vibrator 402 described in the second modified example and the heater 404 described in the third modified example may be provided, for example, on the plate surface 202a.

[0103] [Second embodiment] Next, a second embodiment of the present invention will be described with reference to FIGS. 4A and 4B. In the light source modules and metasurface elements of the second and subsequent embodiments below, the same reference numerals are used to designate components that are common to the light source modules and metasurface elements of the higher-level embodiments, and descriptions thereof will be omitted. The light source modules of the second and subsequent embodiments will be mainly described with respect to the components that are different from the light source modules of the higher-level embodiments.

[0104] Although not shown, the third light source module 1B of the second embodiment includes a metasurface element 216 shown in Fig. 7 as the despeckle element 201, instead of the metasurface element 211 of the first embodiment in the third light source module 1B shown in Fig. 2. Fig. 7 is a side view of the metasurface element 216 of the second embodiment as seen from the Y direction.

[0105] As shown in FIG. 7, the metasurface element 216 includes a substrate 202 and a plurality of microstructures 204. However, while the metasurface element 211 of the first embodiment has the plurality of microstructures 204 provided only on the plate surface 202a of the substrate 202, the metasurface element 216 of the second embodiment has the plurality of microstructures 204 provided on both plate surfaces 202a and 202b of the substrate 202. The plate surfaces 202a and 202b are parallel to each other and parallel to the Z direction. That is, the metasurface element 216 is an element in which the plurality of microstructures 204 are provided on the plate surface (second reference plane) 202b on the +X side of the substrate 202 of the metasurface element 211. The metasurface element 216 has the same configuration as the metasurface element 211, except that the plurality of microstructures 204 are provided on the plate surface 202b as described above.

[0106] The microstructures 204 provided on the plate surface 202b of the substrate 202 have a width d in a direction parallel to the plate surface 202b and a height t1 in the X direction (direction intersecting the reference plane) perpendicular to the plate surface 202b. A plurality of microstructures 204 are arranged on the plate surface 202b. The plurality of microstructures 204 provided on the plate surface 202b are arranged at a desired interval p in the Z direction.

[0107] In metasurface element 216, each of the multiple microstructures 204 provided on plate surface 202b of substrate 202 is aligned in the YZ plane with each of the multiple microstructures 204 provided on plate surface 202a of substrate 202. Here, the YZ plane means "a direction parallel to the first reference plane and the second reference plane" in the claims described below.

[0108] As described above, the metasurface element 216 of the second embodiment includes the substrate 202 and at least one microstructure 204. In the metasurface element 216 of the second embodiment, at least one of the height t1 and the width d of the plurality of microstructures 204 is set to an initially set phase modulation amount φ BThe metasurface element 216 of the second embodiment, like the metasurface element 211 of the first embodiment, is configured with the substrate 202 and the microstructure 204 having dimensions approximately the same as the wavelength band of the blue laser light B, and therefore an ultra-thin and small despeckle element 201 can be realized.

[0109] In the metasurface element 216 of the second embodiment, the substrate (base material) 202 has a plate surface 202b parallel to the plate surface 202a. The metasurface element 216 further includes a microstructure 204 arranged on the plate surface 202b in addition to the plate surface 202a. The microstructure 204 arranged on the plate surface 202b has a width d in a direction along the YZ plane and a height t1 in the X direction intersecting with the plate surface 202b. In the microstructure 204 arranged on the plate surface 202b as well, at least one of the height t1 and the width d is set to a value that is equal to the phase modulation amount φ required for the blue laser light B passing through the microstructure 204. B It is set according to the

[0110] In the metasurface element 216 of the second embodiment, each of the multiple microstructures 204 arranged on the plate surface 202a of the substrate 202 and each of the multiple microstructures 204 arranged on the plate surface 202b are aligned with each other along the YZ plane parallel to the plate surfaces 202a and 202b. According to the metasurface element 216 of the second embodiment, the phase modulation amount φ, which depends on the height t1, is smaller than that of the configuration in which the microstructures 204 are formed only on the plate surface 202a of the substrate 202. B For example, when the height t1 of the microstructures 204 arranged on the plate surface 202a is equal to the height t1 of the microstructures 204 arranged on the plate surface 202b, the metasurface element 216 can achieve a phase modulation amount φ B The phase modulation amount is twice that of (2×φ B ) can be realized.

[0111] As explained in the first embodiment, the multiple microstructures 204 of the metasurface element 216 of the second embodiment are fabricated by methods such as RIE, EIB, nanoimprint lithography, etc., and the higher the height t1, the higher the difficulty of fabrication. In other words, when a structure with a high height t1 is fabricated, the shape of the microstructures 204, which are originally rectangular when viewed in a direction parallel to the YZ plane, becomes tapered, or dimensional errors such as variations in the height t1 are likely to occur. However, according to the metasurface element 216 of the second embodiment, the height t1 of the microstructures 204 formed on each of the plate surfaces 202a and 202b of the substrate 202 is set to a value equal to the phase modulation amount φ required for the metasurface element 216. B is lower than the phase modulation amount φ required for the metasurface element 216. B Half of (φ B / 2). This makes it possible to reduce the difficulty of manufacturing the metasurface element 216 of the second embodiment compared to the difficulty of manufacturing the metasurface element 211 of the first embodiment. In other words, when the height t1 of the microstructure 204 formed on each of the plate surfaces 202a and 202b of the substrate 202 is close to the manufacturing limit of methods such as RIE, EIB, and nanoimprint lithography, the phase modulation amount φ that can be accurately realized by the metasurface element 216 of the second embodiment can be reduced to B The phase modulation amount φ that can be accurately realized by the metasurface element 211 of the first embodiment B can be increased more than

[0112] As another aspect of the metasurface element 216 of the second embodiment, each of the multiple microstructures 204 arranged on the plate surface 202a of the substrate 202 and each of the multiple microstructures 204 arranged on the plate surface 202b of the substrate 202 may be offset from each other along the YZ plane. The amount of offset between the multiple microstructures 204 arranged on the plate surface 202b of the substrate 202 and the multiple microstructures 204 arranged on the plate surface 202a of the substrate 202 is, for example, shorter than the maximum value of the spacing p and shorter than the average value of the spacing p among the multiple microstructures 204. The amount of offset is preferably adjusted appropriately so that the spacing p between the microstructures 204 arranged on the plate surfaces 202a and 202b of the substrate 202 does not disappear when viewed along the X direction, and is preferably set to such an extent that the randomness of the phase modulation pattern realized by the multiple microstructures 204 is not reduced.

[0113] Furthermore, in the second embodiment and the above-mentioned alternative metasurface element 216, multiple microstructures 204 are arranged on each of the plate surfaces 202a, 202b of the substrate 202, but it is sufficient that at least one microstructure 204 is arranged on each of the plate surfaces 202a, 202b of the substrate 202, and one microstructure 204 may also be arranged.

[0114] <First Modification> A metasurface element 217 shown in FIGS. 8A and 8B is a first modified example of the metasurface element 216 according to the second embodiment and the other aspects described above. FIG. 8A is a side view of the metasurface element 217 of the first modified example as viewed from the Y direction. FIG. 8B is a plan view of the metasurface element 217 as viewed from the X direction. As shown in FIGS. 8A and 8B, the metasurface element 217 is partitioned into multiple regions S1, S2, and S3 along the radial direction of the plate surfaces 202a and 202b of the substrate 202. The phase modulation amount of the blue laser light B passing through the region S1 closest to the center of the plate surfaces 202a and 202b is, for example, 0 to 2π. The phase modulation amount of the blue laser light B passing through the region S2 on the plate surfaces 202a and 202b, which is located outside the region S1, is, for example, 0 to π. The phase modulation amount of the blue laser light B passing through the region S3 on the plate surfaces 202a and 202b, which is located outside the region S2, is, for example, 0 to (π / 2).

[0115] According to the metasurface element 217 of the second embodiment and the first modified example of the metasurface element 216 of the above-described alternative aspect, similarly to the first modified example of the first embodiment, the element is divided into a plurality of regions in the radial direction when viewed in the X direction, i.e., from the optical axis AX1 shown in FIG. 2, and the maximum phase modulation amount for the blue laser light B passing through each region is reduced toward the outermost region in the radial direction. Therefore, the divergence angle of the blue laser light DB emitted toward the +X side by the plurality of microstructures 204 in the radially outer regions of the plate surfaces 202a and 202b can be reduced more than that of the radially inner region of the plate surface 202a. This reduces the amount of blue laser light DB leaking outside the metasurface element 217 in the YZ plane, i.e., outside the processing target region of the third light source module 1B, thereby improving the utilization efficiency of the blue laser light DB.

[0116] <Second Modification> A metasurface element 218 shown in FIG. 9 is a second modified example of the metasurface element 216 of the second embodiment and the other aspects described above. FIG. 9 is a side view of the metasurface element 218 of the second modified example as viewed from the Y direction. As shown in FIG. 9, in the metasurface element 217, an oscillator 402 is provided on the side surface 202c of the substrate 202. When the oscillator 402 is activated, the metasurface element 218 vibrates in any direction parallel to the YZ plane, and hardly vibrates in the X direction. The oscillator 402 may be provided at any position on the substrate 202 as long as it does not interfere with the blue laser light B, and may be disposed on the side surface 202d of the substrate 202, for example.

[0117] In the metasurface element 218 of the second embodiment and the second modified example of the metasurface element 216 of the other aspect described above, similarly to the second modified example of the first embodiment, the oscillator 402 is activated to change the position of the microstructure 204 in the YZ plane, and therefore the phase modulation pattern for the incident blue laser light B changes over time. As a result, the spatial distribution of the phase modulation formed by the microstructure 204 changes over time, and speckle noise in the blue laser light DB is superimposed over time. According to the metasurface element 218 of the second modified example, the oscillator 402 is used to change the phase modulation pattern for the blue laser light B over time, and the despeckle effect in the blue laser light DB can be enhanced compared to the metasurface element 216 of the second embodiment.

[0118] In addition, in the metasurface element 218 of the second modified example, as in the first modified example, when viewed from the X direction, it may be divided into multiple regions in the radial direction, and the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer.

[0119] <Third Modification> A metasurface element 219 shown in FIG. 10 is a third modified example of the metasurface element 216 of the second embodiment and the other aspects described above. FIG. 10 is a side view of the metasurface element 219 of the third modified example as viewed from the Y direction. As shown in FIG. 10, in the metasurface element 219, heaters 404 are provided on the side surfaces 202c and 202d of the substrate 202. The multiple microstructures 204 of the metasurface element 219 are formed from a material that transmits blue laser light B and changes volume by contracting or expanding with a temperature change, or a material that changes phase between an amorphous state and a crystalline state. The volume change or phase change of the microstructures 204 is reversible with a temperature change.

[0120] In the metasurface element 219 of the third modified example of the metasurface element 216 of the second embodiment and the above-described other aspect, similarly to the third modified example of the first embodiment, the heater 404 is operated, and the temperature of at least a plurality of microstructures 204 changes within a range in which the material of the microstructures 204 can contract or expand, whereby the size of each of the microstructures 204 arranged on the plate surfaces 202a and 202b of the substrate 202, i.e., the width d, the height t1 of the microstructures 204, and the interval p between the microstructures 204, changes according to the temperature, and the phase modulation amount φ for the blue laser light B is B Alternatively, the heater 404 is operated, and the temperature of the plurality of microstructures 204 arranged on the plate surfaces 202a and 202b of the substrate 202 changes within a range in which a phase change between an amorphous state and a crystalline state is possible, whereby the refractive power of each of the microstructures 204 arranged on the plate surfaces 202a and 202b and the phase modulation amount φ B According to the metasurface element 219 of the third modification, the phase modulation amount φ of the blue laser light B passing through the microstructure 204 is changed by temperature control using the heater 404. B is changed over time, thereby changing over time the phase modulation pattern of the plurality of microstructures 204 for the blue laser light B. According to the metasurface element 219 of the third modified example, it is possible to enhance the randomness of the phase modulation pattern for the blue laser light B and the despeckle effect in the blue laser light DB compared to the metasurface element 216 of the second embodiment.

[0121] In addition, in the metasurface element 219 of the third modified example, as in the first modified example, when viewed from the X direction, it is divided into multiple regions in the radial direction, and the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer.

[0122] Furthermore, the metasurface element 219 of the third modified example may further include an oscillator 402 that vibrates the substrate 202 and the plurality of microstructures 204 arranged on each of the plate surfaces 202a and 202b of the substrate 202, which are integrally formed with each other, in a direction parallel to the YZ plane, as in the second modified example.

[0123] [Third embodiment] Next, a third embodiment of the present invention will be described with reference to FIG. Although not shown, the third light source module 1B of the third embodiment has a composite metasurface element 221 shown in Fig. 11 as the despeckle element 201, instead of the metasurface element 211 of the first embodiment in the third light source module 1B shown in Fig. 2. Fig. 11 is a side view of the composite metasurface element 221 of the third embodiment as seen from the Y direction.

[0124] As shown in FIG. 7, the composite metasurface element (metasurface element) 221 includes a metasurface element (first metasurface section) 211A and a metasurface element (second metasurface section) 211B. Similar to the metasurface element 211 of the first embodiment, each of the metasurface elements 211A and 211B includes a substrate 202 and a plurality of microstructures 204 provided on a surface 202a of the substrate. In the composite metasurface element 221, the surface 202b of the base material 202 of the metasurface element 211A and the surface 202b of the base material 202 of the metasurface element 211B face each other with a gap in the X direction. In the composite metasurface element 221, each of the microstructures 204 provided on the surface 202a of the metasurface element 211A is aligned in the YZ plane with each of the microstructures 204 provided on the surface 202a of the metasurface element 211B.

[0125] As described above, the composite metasurface element 221 of the third embodiment includes metasurface elements 211A and 211B. Each of the metasurface elements 211A and 211B has a substrate (base material) 202 having at least a plate surface 202a, and a plurality of microstructures 204 arranged on the plate surface 202a. Each of the plurality of microstructures 204 has a width d in the YZ direction and a height t1 in the X direction perpendicular to the plate surface 202a. Note that the width d and height t1 are not shown in FIG. 11. At least one of the height t1 and the width d of the plurality of microstructures 204 of each of the metasurface elements 211A and 211B is proportional to the phase modulation amount φ of the blue laser light B passing through the plurality of microstructures 204. B The composite metasurface element 221 of the third embodiment is configured, like the metasurface element 211 of the first embodiment, with a substrate 202 and a microstructure 204 having dimensions comparable to the wavelength band of the blue laser light B, and therefore, it is possible to realize a despeckle element 201 that is ultra-thin and small compared to conventional diffusers and the like.

[0126] In the composite metasurface element 221 of the third embodiment, the metasurface elements 211A and 211B are arranged with a small gap in the X direction so that the plate surfaces 202a of the substrates 202 of the metasurface elements 211A and 211B face each other. In the composite metasurface element 221 of the third embodiment, each of the multiple microstructures 204 arranged on the plate surface 202a of the substrate 202 and each of the multiple microstructures 204 arranged on the plate surface 202b are aligned with each other along the YZ plane parallel to the plate surfaces 202a and 202b. According to the composite metasurface element 221 of the third embodiment, similar to the metasurface element 216 of the second embodiment, the phase modulation amount φ that depends on the height t1 is smaller than that of the single metasurface element 211 in which the microstructures 204 are formed on the plate surface 202a of the substrate 202. B The range of

[0127] The multiple microstructures 204 of the composite metasurface element 221 of the third embodiment are fabricated by methods such as RIE, EIB, nanoimprint lithography, etc., as explained in the first embodiment, and the higher the height t1, the higher the difficulty of fabrication. Even when processing the plate surfaces 202a and 202b of the substrate 202, i.e., processing both sides of the substrate 202, is difficult as in the fabrication of the metasurface element 216 of the second embodiment, the composite metasurface element 221 of the third embodiment has a phase modulation amount φ that depends on the height t1, which is smaller than that of the single metasurface element 211. B This makes it possible to reduce the difficulty of fabricating the metasurface elements 211A and 211B of the composite metasurface element 221 of the third embodiment to the same level as the difficulty of fabricating the metasurface element 211 of the first embodiment.

[0128] In the composite metasurface element 221 of the third embodiment, when the height t1 of the microstructure 204 formed on each of the plate surfaces 202a or 202b of the substrate 202 of each of the metasurface elements 211A and 211B is close to the fabrication limit of methods such as RIE, EIB, and nanoimprint lithography, the phase modulation amount φ that can be accurately realized in the metasurface element 216 of the second embodiment is B The phase modulation amount φ that can be accurately realized by the metasurface element 211 of the first embodiment B can be increased more than

[0129] As another aspect of the composite metasurface element 221 of the third embodiment, each of the plurality of microstructures 204 arranged on the plate surface 202a of the substrate 202 of the metasurface element 211A and each of the plurality of microstructures 204 arranged on the plate surface 202a of the metasurface element 211B may be offset from each other along the YZ plane. As in the second embodiment, the amount of offset of the plurality of microstructures 204 arranged on the metasurface element 211B relative to the plurality of microstructures 204 arranged on the metasurface element 211A is preferably adjusted appropriately so that the spacing between the microstructures 204 arranged on the metasurface elements 211A and 211B does not disappear when viewed along the X direction, and is preferably set so that the randomness of the phase modulation pattern realized by the plurality of microstructures 204 is not reduced.

[0130] Furthermore, in the second embodiment and the above-mentioned alternative composite metasurface element 221, multiple microstructures 204 are arranged on each of the plate surfaces 202a of the substrates 202 of the metasurface elements 211A and 211B, but it is sufficient that at least one microstructure 204 is arranged on each of the plate surfaces 202a of the substrates 202, and one microstructure 204 may also be arranged.

[0131] <First Modification> In the third embodiment and the first modified example of the composite metasurface element 221 of the other aspect described above, although not shown, the plate surface 202a of the substrate 202 of at least one of the metasurface elements 211A and 211B may be partitioned into a plurality of regions along the radial direction. In the first modified example of the composite metasurface element 221, the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer when viewed in the X direction, i.e., from the optical axis AX1 shown in Figure 2.

[0132] In the second embodiment and the first modified example of the composite metasurface element 221 of the other aspect described above, the diffusion angle of the blue laser light DB emitted to the +X side by the multiple microstructures 204 in the radially outer region of the plate surface 202a can be made smaller than that in the radially inner region of the plate surface 202a. According to the first modified example of the composite metasurface element 221, the blue laser light DB leaking outside the composite metasurface element 221 in the YZ plane, i.e., outside the processing target region of the third light source module 1B equipped with the composite metasurface element 221, can be reduced, thereby improving the utilization efficiency of the blue laser light DB.

[0133] <Second Modification> A second modified example of the composite metasurface element 221 of the third embodiment and the other aspects described above is a composite metasurface element 223 shown in Figure 12. Figure 12 is a side view of the composite metasurface element 223 of the second modified example as viewed from the Y direction. In the composite metasurface element 223 of the second modified example, an oscillator 402 is provided on the side surface 202c of the substrate 202 of the metasurface element 213. That is, as shown in Figure 12, in the composite metasurface element 223 of the second modified example, the plate surface 202b of the base material 202 of the metasurface element 211 and the plate surface 202b of the base material 202 of the metasurface element 213 face each other in the X direction with a gap between them.

[0134] In the composite metasurface element 223, each of the multiple microstructures 204 provided on the plate surface 202a of the metasurface element 211 is aligned in the YZ plane with each of the multiple microstructures 204 provided on the plate surface 202a of the metasurface element 213. When the oscillator 402 is activated, the metasurface element 213 vibrates in any direction parallel to the YZ plane, and vibrates very little in the X direction. The oscillator 402 may be provided at any position on the substrate 202 as long as it does not interfere with the blue laser light B, and may be disposed on the side surface 202d of the substrate 202, for example.

[0135] In the composite metasurface element 223 of the second modified example of the metasurface element 216 of the third embodiment and the other aspect described above, as in the second modified example of the second embodiment, the oscillator 402 is activated, changing the position of the microstructure 204 of the metasurface element 213 in the YZ plane, and therefore the phase modulation pattern for the incident blue laser light B changes over time. As a result, the spatial distribution of the phase modulation formed by the microstructure 204 of the metasurface element 213 changes over time, and speckle noise in the blue laser light DB is superimposed over time. According to the composite metasurface element 223 of the second modified example, the oscillator 402 is used to change the phase modulation pattern for the blue laser light B over time, thereby improving the despeckle effect in the blue laser light DB compared to the composite metasurface element 221 of the third embodiment and the other aspect described above.

[0136] In the composite metasurface element 223 of the second modified example, an oscillator 402 is provided on the side surface 202c of the substrate 202 of at least one of the metasurface elements 211A and 211B of the composite metasurface element 221 of the third embodiment. That is, an oscillator 402 may be provided on the side surface 202c of the substrate 202 of the metasurface element 211 in addition to the metasurface element 213 of the composite metasurface element 221 of the third embodiment. Of the metasurface elements 211 and 213 of the composite metasurface element 221 of the third embodiment, an oscillator 402 may be provided on the side surface 202c of the substrate 202 of only the metasurface element 211.

[0137] Furthermore, in at least one of the metasurface elements 211, 213 of the composite metasurface element 223 of the second modified example, as in the first modified example, when viewed from the X direction, it may be divided into multiple regions in the radial direction, and the more radially outer the region, the lower the maximum phase modulation amount for the blue laser light B passing through each region.

[0138] <Third Modification> A third modified example of the composite metasurface element 221 of the third embodiment and the above-described alternative embodiment is a composite metasurface element 224 shown in FIG. 13. FIG. 13 is a side view of the composite metasurface element 224 of the third modified example as viewed from the Y direction. In the composite metasurface element 224, heaters 404 are provided on the side surfaces 202c and 202d of the substrate 202 of the metasurface element 211B, one of the metasurface elements 211A and 211B of the composite metasurface element 221 of the third embodiment. In the composite metasurface element 224 of the third modified example, the multiple microstructures 204 provided on the plate surface 202a of the substrate 202 of the metasurface element 211B of the composite metasurface element 221 of the third embodiment are formed of a material that transmits blue laser light B and changes volume by shrinking or expanding with a change in temperature, or a material that changes phase between an amorphous state and a crystalline state. The volume change or phase change of the microstructure 204 is reversible with respect to a temperature change. That is, as shown in Fig. 13, in the composite metasurface element 224 of the third modified example, the plate surface 202b of the substrate 202 of the metasurface element 211A and the plate surface 202b of the substrate 202 of the metasurface element 214 face each other in the X direction with a gap therebetween.

[0139] In the composite metasurface element 224 of the third embodiment and the third modified example of the composite metasurface element 221 of the other aspect described above, similarly to the third modified example of the second embodiment, the heater 404 is operated, and the temperature of at least a plurality of microstructures 204 of the metasurface element 214 changes within a range in which the material of the microstructures 204 can contract or expand, whereby the size of each microstructure 204 arranged on the plate surface 202a of the substrate 202 of the metasurface element 214, i.e., the width d, height t1 of the microstructure 204, and the interval p between the microstructures 204, changes according to the temperature, and the phase modulation amount φ for the blue laser light B BAlternatively, the heater 404 is operated, and the temperature of the plurality of microstructures 204 arranged on the plate surface 202 a of the substrate 202 of the metasurface element 214 changes within a range in which the phase can change between the amorphous state and the crystalline state, thereby changing the refractive power of each of the microstructures 204 arranged on the plate surface 202 a of the metasurface element 214 and the phase modulation amount φ B According to the composite metasurface element 224 of the third modification, the phase modulation amount φ of the blue laser light B passing through the microstructure 204 of the metasurface element 214 is changed by temperature control using the heater 404. B is changed over time, thereby changing over time the phase modulation pattern of the multiple microstructures 204 of the metasurface element 214 for the blue laser light B. According to the composite metasurface element 224 of the third modified example, the randomness of the phase modulation pattern for the blue laser light B and the despeckle effect in the blue laser light DB can be improved compared to the composite metasurface element 221 of the third embodiment.

[0140] In the composite metasurface element 224 of the third modification, a heater 404 is provided on the side surfaces 202c, 202d of the substrate 202 of at least one of the metasurface elements 211A, 211B of the composite metasurface element 221 of the third embodiment, and the plurality of microstructures 204 of at least one of the elements is formed of a material that transmits blue laser light B and contracts or expands with a temperature change to change its volume, or a material that changes phase to either an amorphous or crystalline state. That is, in addition to the metasurface element 211B of the composite metasurface element 221 of the third embodiment, an oscillator 402 is provided on the side surface 202c of the substrate 202 of the metasurface element 211A, and the plurality of microstructures 204 of the metasurface element 211A may be formed of a material that transmits blue laser light B and contracts or expands with a temperature change to change its volume, or a material that changes phase to either an amorphous or crystalline state. Of the metasurface elements 211A and 211B of the composite metasurface element 221 of the third embodiment, only the metasurface element 211A has an oscillator 402 provided on the side 202c of the substrate 202, and the multiple microstructures 204 of the metasurface element 211A may be formed from a material that transmits blue laser light B and changes volume by contracting or expanding with temperature changes, or a material that changes phase to either an amorphous or crystalline state.

[0141] Furthermore, in at least one of the metasurface elements 211, 214 of the composite metasurface element 224 of the third modified example, as in the first modified example, the element may be divided into multiple regions radially when viewed from the X direction, and the maximum phase modulation amount for the blue laser light B passing through each region may be reduced as the region becomes more radially outer.

[0142] Furthermore, at least one of the metasurface elements 211, 214 of the composite metasurface element 224 of the third modified example may further include an oscillator 402 that vibrates the substrate 202 and the multiple microstructures 204 arranged on the plate surface 202a of the substrate 202, which are integrally formed with each other, of the metasurface element 214, in a direction parallel to the YZ plane, as in the second modified example.

[0143] Furthermore, in the composite metasurface element 221 of the third embodiment and the first modified example, the composite metasurface element 223 of the second modified example of the third embodiment, and the composite metasurface element 224 of the third modified example of the third embodiment, each of the metasurface elements 211A, 211, 211 and each of the metasurface elements 211B, 213, 214 facing each other in the X direction may be adhered to each other by an adhesive not shown.

[0144] In the composite metasurface element 221 of the third embodiment and the first modified example, the composite metasurface element 223 of the second modified example of the third embodiment, and the composite metasurface element 224 of the third modified example of the third embodiment, the thickness of each of the metasurface elements 211A, 211, 211 and the metasurface elements 211B, 213, 214 that face each other in the X direction, i.e., the size in the X direction, can be kept to a dimension on the order of the wavelength, thereby achieving ultra-thinness. Therefore, each of the metasurface elements 211A, 211, 211 and each of the metasurface elements 211B, 213, 214 can be concentrated and arranged at position PS3 that is substantially conjugate to position PS4.

[0145] [Fourth embodiment] Next, a fourth embodiment of the present invention will be described with reference to FIGS.

[0146] (projector) 14 is a schematic configuration diagram of a projector 102 according to the fourth embodiment. Similar to the projector 100 according to the first embodiment, the projector 102 is a projection-type image display device that projects an image onto a screen SCR. As shown in FIG. 14, the projector 102 includes a white light source module 1W for white light, field lenses 90B, 90G, and 90R, dichroic mirrors 110 and 114, reflecting mirrors 112, 116, and 118, relay lenses 132 and 134, light modulation elements 95B, 95G, and 95R, a cross dichroic prism 3, and a projection optical system (projection device) 4.

[0147] The white light source module 1W emits white light (light) DW that is synthesized from yellow light YY that includes red light and green light and blue laser light DB. The configuration of the white light source module 1W will be described later.

[0148] The white light DW emitted from the white light source module 1W is separated into red light, green light, and blue light by dichroic mirrors 110, 114, reflecting mirrors 112, 116, 118, and relay lenses 132, 134, and each of the separated red light, green light, and blue light is guided to each of the light modulation elements 95B, 95G, 95R.

[0149] Dichroic mirror 110 passes blue light BB of white light DW incident from the -X side along optical axis AX1 and reflects green light GG and red light RR, i.e., yellow light. Each of blue light BB, green light GG, and red light RR contained in white light DW is emitted from white light source module 1W in a despeckle-treated state. Reflecting mirror 112 reflects almost all of the incident green light GG and red light RR. Dichroic mirror 114 reflects green light GG of the incident green light GG and red light RR and passes red light RR. Each of reflecting mirrors 116 and 118 reflects almost all of the incident red light RR.

[0150] Field lenses 90B, 90G, and 90R are disposed on the optical paths of blue light BB, green light GG, and red light RR, respectively, facing side surfaces 3b, 3g, and 3r of cross dichroic prism 3, and on the -X, -Z, and +X sides of side surfaces 3b, 3g, and 3r of cross dichroic prism 3. Light modulation elements 95B, 95G, and 95R are disposed on the optical paths of blue light BB, green light GG, and red light RR, respectively, between field lenses 90B, 90G, and 90R and cross dichroic prism 3.

[0151] Field lenses 90B, 90G, and 90R are arranged at a predetermined distance on the optical path of white light DW from superimposing lens 82 of white light source module 1W (described later) and are located ahead of superimposing lens 82 in the direction of travel of white light DW. Field lenses 90B, 90G, and 90R align the travel directions of the outer peripheries of blue light BB, green light GG, and red light RR contained in white light DW emitted from superimposing lens 82 in the YZ plane, and emit the aligned blue light BB, green light GG, and red light RR toward the +X side along the X direction. Field lenses 90B, 90G, and 90R suppress attenuation and reduction in clarity of the incident white light DW.

[0152] Blue light BB transmitted through dichroic mirror 110 passes through field lens 90B and enters the image forming area of ​​light modulation element 95B. Green light GG reflected by dichroic mirror 110 is reflected in turn by reflecting mirror 112 and dichroic mirror 114, passes through field lens 90G, and enters the image forming area of ​​light modulation element 95G. Red light RR reflected by dichroic mirror 110 is reflected by reflecting mirror 112, passes through dichroic mirror 114, is reflected in turn by reflecting mirrors 116 and 118, passes through field lens 90R, and enters the image forming area of ​​light modulation element 95R.

[0153] Each of the light modulation elements 95B, 95G, and 95R is composed of a liquid crystal panel that modulates the incident blue light BB, green light GG, and red light RR in accordance with image information to form an image. The operating mode of the liquid crystal panel may be any of TN mode, VA mode, transverse electric field mode, etc., and is not limited to a specific mode. Each of the light modulation elements 95R, 95G, and 95B includes an incident-side polarizing plate (not shown) arranged on the light incident surface side and an exit-side polarizing plate (not shown) arranged on the light exit surface side. Each of the light modulation elements 95B, 95G, and 95R generates blue image light LB, green image light LG, and red image light LR, respectively.

[0154] Image light LB emitted from light modulation element 95B is incident on side surface 3b of cross dichroic prism 3 from the -X side parallel to the X direction. Image light LG emitted from light modulation element 95G is incident on side surface 3g of cross dichroic prism 3 from the -Z side parallel to the Z direction. Image light LR emitted from light modulation element 95R is incident on side surface 3r of cross dichroic prism 3 from the +X side parallel to the X direction. Cross dichroic prism 3 combines the image light emitted from each of light modulation elements 95B, 95G, and 95R to form a color image.

[0155] As with the projector 100 of the first embodiment, the light LL combined by the cross dichroic prism 3 is emitted to the +Z side along the Z direction and projected onto the screen SCR by the projection optical system 4. An enlarged image is displayed on the screen SCR.

[0156] (light source module) Fig. 15 is a schematic configuration diagram of a white light source module 1W of the fourth embodiment. As shown in Fig. 15, the white light source module 1W includes a light source unit 10, a condenser lens 21, a fluorescence rotating element 130, a pickup optical system 40, despeckle condensing elements 205 and 207, a second lens array 60, a polarization conversion element 70, and superimposing lenses 81 and 82. In the white light source module 1W, the above-mentioned components are arranged in the order shown from the -X side to the +X side along the X direction.

[0157] The blue laser light B condensed by the condensing lens 21 is incident on the fluorescence rotation element 130. The fluorescence rotation element 130 includes a disk 131, a phosphor layer 135, a dichroic film 140, and a motor 32. The disk 131 extends in the YZ plane and has plate surfaces 131a and 131b that are circular when viewed along the X direction. The disk 131 is configured to be rotatable about a rotation axis RX passing through the center of the plate surface 131b by the motor 32 provided on the plate surface 131b on the +X side. The disk 131 is formed of a material that transmits at least the blue laser light B. Examples of materials for the disk 131 include quartz, crystal, sapphire, optical glass, and transparent resin.

[0158] A diffusion element (not shown) may be disposed between the condenser lens 21 and the fluorescence rotating element 130 in the X direction. The diffusion element is formed to be larger than the beam diameter of the blue laser light B in a plane parallel to the YZ plane, and may be configured as a diffusion plate similar to the diffusion element 30 described in the first embodiment.

[0159] The phosphor layer 135 is disposed on the plate surface 131b of the disk 131 in the X direction via the dichroic film 140. The phosphor layer 135 is provided in an area that overlaps with the optical axis AX1 in the radial direction of the plate surface 131a and over the entire circumferential direction of the plate surface 131b. Blue laser light B that has passed through the disk 131 and the dichroic film 140 is incident on the phosphor layer 135.

[0160] The phosphor layer 135 generates yellow light YY using at least a portion of the incident blue laser light B as excitation light. The yellow light YY has a yellow wavelength band (second wavelength band) that is different from the blue wavelength band within the visible wavelength band, and includes green light and red light. The phosphor layer 135 is made of, for example, (Y,Gd)3(Al,Ga)5O, which is a type of YAG-based phosphor. 12 The dichroic film 140 is provided between the disk 131 and the phosphor layer 135 in the X direction, and transmits the blue laser light B and reflects the yellow light YY.

[0161] At least a portion of the remaining blue laser light B (a portion of the light in the first wavelength band) of the blue laser light B that entered phosphor layer 135 from the -X side passes through phosphor layer 135. The other portion of the blue laser light B that entered phosphor layer 135 is backscattered and emitted to the -X side. Yellow light YY generated in phosphor layer 135 and emitted to the -X side is reflected by dichroic film 140, passes through phosphor layer 135, and travels to the +X side along optical axis AX1. Blue laser light B that passed through phosphor layer 135 and yellow light YY generated by the wavelength conversion function of phosphor layer 135 are emitted from phosphor layer 135 to the +X side along optical axis AX1.

[0162] The despeckle condensing elements 205 and 207 are arranged at a predetermined distance in the X direction from the pickup optical system 40 and on the +X side of the second lens 42 of the pickup optical system 40. The despeckle condensing elements 205 and 207 are arranged on the optical axis AX1 at a position PS3 conjugate to a position PS4 of the image forming region of each of the light modulation elements 95B, 95G, and 95R.

[0163] The despeckle focusing elements 205 and 207 have multiple metasurface elements 231 and 232 for splitting the blue laser light DB and yellow light YY emitted from the pickup optical system 40 into multiple partial beams in the YZ plane. The metasurface element 231 acts as a despeckle element for the incident blue laser light B and acts as a condenser lens for the incident yellow light YY, similar to the microlens 51 described in the first embodiment. The metasurface element 232 acts as a condenser lens only for the incident blue laser light B, similar to the microlens 51. Therefore, the blue laser light B and yellow light YY that pass through the despeckle focusing elements 205 and 207 are subjected to despeckle countermeasures and are split into multiple partial beams in the YZ plane. The metasurface elements 231 and 232 will be described later.

[0164] The multiple metasurface elements 231, 232 are arranged in the Y and Z directions within the YZ plane. The despeckle focusing elements 205, 207 emit the blue laser light DB and the yellow light DY, which have been split into multiple partial beams, toward the +X side along the X direction.

[0165] The multiple microlenses 61 of the second lens array 60 are arranged corresponding to the multiple metasurface elements 231, 232 of the despeckle condensing elements 205, 207. The second lens array 60, together with the superimposing lenses 81, 82, forms images of the multiple metasurface elements 231, 232 of the despeckle condensing elements 205, 207 near the image forming regions of each of the light modulation elements 95B, 95G, 95R.

[0166] The polarization conversion element 70 converts each partial light beam split by the despeckle condensing elements 205 and 207 into predetermined linearly polarized light according to the characteristics of each of the light modulation elements 95B, 95G, and 95R. The despeckle condensing elements 205 and 207, the second lens array 60, and the superimposing lenses 81 and 82 constitute an integrator optical system that makes uniform the in-plane light intensity distribution of the blue laser light B and the yellow light YY, or the light LL, in the image formation area of ​​the projector 102.

[0167] The white light LW emitted from the white light source module 1W enters the cross dichroic prism 3 from the side surface 3b in the projector 102 shown in FIG.

[0168] 14 and 15, in the projector 102, by despeckling the blue laser light B at position PS3, the effect of this despeckling is highly apparent in the blue light BB that is incident on the light modulation element 95B at position PS4. Also, since the image lights LB, LG, and LR are formed by the blue light BB that has already been despeckled at position PS4, the incoherent green light GG, and the red light RR, despeckle measures are effectively taken for the light LL that is projected onto the screen SCR described with reference to FIG.

[0169] (Despeckle focusing element) 15, the despeckle focusing element 205 includes a plurality of metasurface elements 251 arranged in the Y and Z directions on the YZ plane. The size and total number of the metasurface elements 251 on the YZ plane correspond to the beam diameter and the number of divisions of the partial light beams when the blue laser light B and yellow light YY incident from the -X side are divided into a plurality of partial light beams on the YZ plane as described above, and are equivalent to the size of the microlenses 61 of the second lens array 60 on the YZ plane and the total number arranged on the YZ plane.

[0170] Figure 16 is a side view showing the state when blue laser light B is incident on the metasurface element 251 of the fourth embodiment. Figure 17 is a side view showing the state when yellow light YY is incident on the metasurface element 251. As shown in Figures 16 and 17, the metasurface element 231 comprises a substrate (base material) 202 having plate surfaces 202a and 202b parallel to the YZ plane, and a plurality of microstructures 206 provided on the plate surface 202b.

[0171] The microstructure 206 has a width d2 in a direction parallel to the plate surface 202b and a height t4 in the X direction (direction intersecting the reference plane) perpendicular to the plate surface 202b. The metasurface element 211 has a plurality of microstructures 204. The widths d2 and heights t4 of the plurality of microstructures 204, and the spacing p2 between the microstructures 204, may be equal to or different from one another.

[0172] The metasurface element 251 randomly modulates the phase of the blue laser light B, which has been expanded and approximately collimated by the pickup optical system 40, for each position within the region of the metasurface element 251 in the YZ plane. As shown in FIG. 16, the isophase surface WF B1 are distributed parallel to the YZ plane. Also, multiple equiphase surfaces WF B1 are distributed at equal intervals in the X direction. In FIG. 16, multiple equal phase surfaces WF B1 One of the equal-phase surfaces WF B1 In the blue laser light DB that has passed through the metasurface element 251, the equiphase surface WFB1 is divided into short parts in the YZ plane and distributed in the X direction as multiple equiphase surfaces WF B2 Such multiple equal phase surfaces WF B2 As a result, blue laser light DB having a random phase distribution is generated. As a result, despeckle focusing element 205 formed by metasurface element 251 randomly modulates the phase of the incident blue laser light B, and emits the phase-modulated blue laser light DB to despeckle focusing element 207.

[0173] On the other hand, the metasurface element 251 focuses the phase of the yellow light YY, which has been expanded and approximately collimated by the pickup optical system 40, to a focal point F on the +X side. As shown in FIG. 17, the equiphase surface WF of the yellow light YY incident on the metasurface element 251 Y1 is the equiphase surface WF of blue laser light B B1 Similarly, they are distributed parallel to the YZ plane. Also, multiple equiphase surfaces WF Y1 are distributed at equal intervals in the X direction. In FIG. 17, multiple equal phase surfaces WF Y1 One of the equal-phase surfaces WF Y1 In the yellow light YY that has passed through the metasurface element 251, the equiphase surface WF Y1 is curved with respect to the YZ plane so as to converge toward a focal point F at a position a predetermined focal distance away from the +X side surface 202b of the substrate +X 202 in the X direction. Y2 In addition, multiple equiphase surfaces WF Y2 are distributed at equal intervals in the radial direction centered on the focal point F. Such multiple equiphase surfaces WF Y2 This generates yellow light YY that is focused at the focal point F. As a result, the despeckle focusing element 205 formed by the metasurface element 251 focuses the phase of the incident yellow light YY toward the focal point F, and while focusing the yellow light YY at the focal point F, it emits the yellow light YY to the microlenses 61 of the second lens array 60 through the despeckle focusing element 207.

[0174] The focal point F of the yellow light YY of the metasurface element 251 is located within the region of the microlens 61 corresponding to the metasurface element 251 in the YZ plane. The blue laser light B and yellow light YY incident on the metasurface element 251 from the -X side are confined within the microstructures 206, each of which has a width d2, height t4, and interval p2 set as described above, and resonate due to this optical confinement. The despeckled blue laser light DB and the focused yellow light YY emitted from the multiple microstructures 206 have a random phase modulation amount φ within the region occupied by the metasurface element 251 in the YZ plane. B and the phase modulation amount φ for imaging yellow light YY within the region. Y occurs.

[0175] The width d2 and height t4 of the microstructure 206 of the metasurface element 251, and the interval p2 between the microstructures 204 are determined according to the peak wavelength of the blue laser light B, and a suitable phase modulation amount φ at which the blue laser light B passing through the microstructure 206 is randomly phase-modulated as described above. B At the same time, a suitable phase modulation amount φ is set according to the peak wavelength of the yellow light YY and such that the yellow light YY passing through the microstructure 206 is focused at the focal point F as described above. Y It is set to achieve this.

[0176] The despeckle focusing element 207 includes a plurality of metasurface elements 261 arranged in the Y and Z directions on the YZ plane. The size and total number of the metasurface elements 261 on the YZ plane correspond to the beam diameter and the number of divisions of the partial light beams when the blue laser light DB incident from the -X side is divided into a plurality of partial light beams on the YZ plane as described above, and are equivalent to the size of the microlenses 61 of the second lens array 60 on the YZ plane and the total number arranged on the YZ plane.

[0177] Although not shown, metasurface element 261, like metasurface element 251, comprises a substrate (base material) 202 having plate surfaces 202a and 202b parallel to the YZ plane, and a plurality of microstructures 206 provided on plate surface 202b.

[0178] However, the metasurface element 261 focuses the phase of the despeckled blue laser light B emitted from the metasurface element 251 to a focal point F on the +X side. On the other hand, the metasurface element 261 does not affect the phase of the yellow light YY emitted from the metasurface element 251 and focused at the focal point F.

[0179] The blue laser light DB and yellow light YY incident on the metasurface element 261 from the -X side are confined in the microstructures 206, each of which has a width d2, height t4, and interval p2 set as described above, and resonate due to this optical confinement. The focused blue laser light emitted from the multiple microstructures 206 is modulated by a phase modulation amount φ that focuses the blue laser light DB within the area occupied by the metasurface element 261 in the YZ plane. B occurs.

[0180] The width d2 and height t4 of the microstructure 206 of the metasurface element 261 and the interval p2 between the microstructures 204 are set to a suitable phase modulation amount φ B At the same time, the yellow light YY passing through the microstructure 206 is set to be not phase-modulated.

[0181] It is preferable that the predetermined values ​​of the width d2, height t4 and spacing p2 of the microstructure 206 of the metasurface elements 251, 261 are set taking into consideration the dimensions that can be produced and processed with high precision and low yield using the material of the microstructure 206 in an apparatus used to manufacture the metasurface elements 251, 261 based on methods such as RIE, FIB and nanoimprint lithography, without excessively exceeding these dimensions.

[0182] In the metasurface elements 251 and 261, the material of the microstructure 206 preferably has a high refractive index for at least the blue laser light B as well as the yellow light YY and has little absorption. By using a material of the microstructure 206 that has a high refractive index for the blue laser light B and the yellow light YY, the phase modulation amount φ that can be obtained for a certain height t4 can be reduced. B , φ YThis increases the degree of freedom in designing the microstructure 206. As the material for the microstructure 206, TiO2, SiN, etc., which have low absorption of light in the visible wavelength range, are preferable.

[0183] As described above, the behavior of the metasurface elements 251, 261, in which the width d2 and height t4 of the microstructures 206 and the spacing p2 between the microstructures 206 are set, when blue laser light B and yellow light YY are incident on each of them is determined using electromagnetic wave analysis such as the FDTD method. In particular, since the metasurface elements 251, 261 realize completely different functions using the blue laser light B and yellow light YY, which are two lights in different wavelength bands, design evaluation to confirm that each function is compatible as desired is important for the white light source module 1W and the projector 102 to operate smoothly.

[0184] Here, we will explain the design guidelines based on the structure of the metasurface element 251 that realizes the light-collecting function. If the central wavelength of the yellow light YY is λ, the predetermined focal length in the X direction of the plate surface 202b of the substrate 202 is f, and the center of the metasurface element 251 in a plane parallel to the YZ plane is taken as the origin, with the coordinate value y in the Y direction and the coordinate value z in the Z direction, the phase distribution ψ(y, z, λ) required for the metasurface element 251 is expressed by the following equation (1).

[0185]

number

[0186] C(λ) in equation (1) is a constant that changes depending on the wavelength λ and is determined by the opening area of ​​the metasurface element 251. Then, based on equation (1), the width d2 and height t4 of the microstructure 206 and the spacing p2 between the multiple microstructures 206 are adjusted. Specifically, any one parameter among the width d2, height t4, and spacing p2 pattern of the microstructures 206 is changed within a predetermined range, and the relationship with the phase of the yellow light YY emitted from the microstructure 206 is calculated using a simulation based on electromagnetic wave analysis such as FDTD.

[0187] FIG. 18 is a graph showing an example of the results of a simulation based on FDTD for the relationship between the width d2 of the microstructure 206 and the phase φ of the light emitted from the microstructure 206. In this simulation, the wavelength λ was set to 550 nm and the focal length f to 250 μm. Although not shown, in the structural model of this simulation, the light receiver was virtually placed on the same side of the metasurface element 251 as the light source in the direction corresponding to the X direction, i.e., parallel to the optical axis of the incident light. In other words, in this simulation, the incident light travels back and forth through the microstructure 206 with height t4 in a direction parallel to the optical axis, and a phase modulation amount φ' is imparted that is approximately twice the phase modulation amount φ that can be achieved at height t4. The vertical axis of the graph in FIG. 18 represents the normalized phase (φ' / 2π) normalized by 2π.

[0188] 18, as the width d2 of the microstructure 206 increases, the phase modulation amount φ' increases nonlinearly and continuously from 0 to a maximum value near 2π. If the width d2 increases further after the phase modulation amount φ' reaches its maximum value, the phase modulation amount φ' suddenly decreases discontinuously to near 0, then increases nonlinearly and continuously from near 0 to the maximum value, repeating such discontinuous decreases and continuous increases. The maximum value of the phase modulation amount φ' decreases as the width d2 increases.

[0189] Next, from the simulation results including the calculation results shown in FIG. 18, the width d2, height t4, and spacing p2 of each of the multiple microstructures 206 that yield the phase distribution ψ(y,z,λ) of equation (1) are determined. FIG. 19 shows an example of the phase distribution ψ(y,z,λ) calculated for the structural model of the metasurface element 251. After calculating the phase distribution ψ(y,z,λ) in this manner, the wavefront shape of the light emitted from the structural model of the metasurface element 251 and the light intensity distribution at a virtual focal point F positioned a focal distance f forward in the optical axis direction from the structural model are calculated using the same FDTD-based simulation. The calculated results are verified, and the width d2, height t4, and spacing p2 between the microstructures 206 are each optimized.

[0190] The metasurface elements 251, 261 of the fourth embodiment described above comprise a substrate 202 and at least one microstructure 206 arranged on the plate surface 202b of the substrate 202. The metasurface elements 251, 261 of the fourth embodiment have the same effects as the metasurface element 211 of the first embodiment with respect to the content common to them.

[0191] In the metasurface element 251 of the fourth embodiment, at least one of the height t4 and width d2 of the microstructure 206 is determined so that the blue laser light (light) B passing through the microstructure 206 is randomly phase-modulated, and the yellow light YY passing through the microstructure 206 is focused by a lens function that narrows the wide radiation angle due to Lambertian emission. The yellow light YY has green and red wavelengths different from the blue wavelength of the blue laser light B, and is an example of "light having a second wavelength different from the first wavelength" in the claims described below. In the metasurface element 261 of the fourth embodiment, at least one of the height t4 and width d2 of the microstructure 206 is determined so that the yellow light (light) YY passing through the microstructure 206 is not phase-modulated, while the blue laser light DB passing through the microstructure 206 is focused. The blue laser light B has a blue wavelength different from the red and green wavelengths of the yellow light YY, and is an example of "light having a second wavelength different from the first wavelength" in the claims described below. The metasurface element 261 of the fourth embodiment emits the blue laser light DB and the yellow light DY, which are despeckled and condensed, toward the microlenses 61 of the second lens array 60.

[0192] According to the metasurface elements 251 and 261 of the fourth embodiment, the microstructure 206 has a common absolute dimension for the blue laser light B and the yellow light YY having different wavelengths, and the phase modulation amount φ B , φ Ycan be obtained. According to each of the metasurface elements 251, 261 of the fourth embodiment, by using the above-mentioned characteristics, it is possible to use a single element to exhibit a despeckle function for one of the blue laser light B and the yellow light YY, which have different wavelengths, and to exhibit a focusing function for the other light. Note that the lens function realized by each of the metasurface elements 251, 261 of the fourth embodiment focuses the yellow light YY or the blue laser light DB by the light confinement effect and resonance phenomenon in the microstructure 206 as described above, and therefore, unlike a refractive lens, almost no chromatic aberration occurs.

[0193] The metasurface elements 251 and 261 of the fourth embodiment use a plurality of microstructures 206 that generate a plurality of resonance modes, such as guided mode resonance, in which Fabry-Perot resonance in the X direction and resonance in a direction parallel to the YZ plane caused by diffraction by the periodic structure of the microstructures 206 are coupled to each other for the blue laser light B or the yellow light YY. Therefore, the phase modulation amount φ is continuously varied in the direction parallel to the YZ plane for at least one of the height t4 and width d2 of the microstructures 206. B , φ Y does not change, but the phase modulation amount φ B , φ Y Therefore, according to each of the metasurface elements 251 and 261 of the fourth embodiment, it is possible to easily design an element that is ultra-thin and small and has different optical functions at different wavelengths.

[0194] According to the projector 102 of the fourth embodiment, the white light source module 1W is provided with ultra-thin and compact despeckle condensing elements 205 and 207, each made up of metasurface elements 251 and 261. This makes it possible to effectively prevent despeckle from occurring in the light LL projected onto the screen SCR while preventing the white light source module 1W from becoming larger. In particular, when the projector 102 is made smaller and lighter, the space available for disposing the despeckle condensing elements in the white light source module 1W is extremely limited. Even in such cases, the despeckle condensing elements 205 and 207, each made up of a plurality of metasurface elements 251 and 261, can be easily disposed at the position PS3 where the despeckle effect of the white light source module 1W is most pronounced, or at other desired positions.

[0195] In the above-described metasurface elements 251, 261 of the fourth embodiment, the multiple microstructures 206 of the metasurface element 261 are aligned with the multiple microstructures 206 of the metasurface element 261 in a direction parallel to the YZ plane. However, the multiple microstructures 206 of the metasurface element 261 may be offset from the multiple microstructures 206 of the metasurface element 261 in a direction parallel to the YZ plane. The amount of offset is preferably adjusted appropriately so that, when viewed along the X direction, the spacing between the microstructures 204 provided on the metasurface elements 251, 261 does not disappear, and the division of the blue laser light B and the yellow light YY into multiple partial beams in the YZ plane is not affected, and the randomness of the phase modulation pattern realized by the multiple microstructures 204 is not reduced.

[0196] In addition, in the metasurface elements 251 and 261 of the fourth embodiment, the microstructures 206 are provided only on the plate surface 202b of the substrate 202, but they may be provided only on the plate surface 202a, for example. The microstructures 206 of the metasurface element 251 may be provided only on one of the plate surfaces 202a and 202b of the substrate 202, and the microstructures 206 of the metasurface element 261 may be provided only on the other of the plate surfaces 202a and 202b of the substrate 202.

[0197] <First Modification and Second Modification> Although not shown, in the metasurface elements 251 and 261 of the fourth embodiment, as in the second variant of the third embodiment, an oscillator 402 may be provided at any position on the substrate 202 of at least one of the metasurface elements 251 and 261.

[0198] Also, although not shown, in the metasurface elements 251 and 261 of the fourth embodiment, as in the third modified example of the third embodiment, the microstructure 204 of at least one of the metasurface elements 251 and 261 may be formed from a material that transmits blue laser light B and yellow light YY and changes volume by shrinking or expanding with temperature changes, or a material that changes phase to either an amorphous or crystalline state.

[0199] In the metasurface elements 251 and 261 according to the modified examples of the fourth embodiment, blue laser light Bφ passing through the microstructure 204 B can be changed over time to change the phase modulation pattern for the blue laser light B. Therefore, according to the metasurface elements 251 and 261 of the modified examples of the fourth embodiment, it is possible to enhance the randomness and despeckle effect of the phase modulation pattern for the blue laser light B and the yellow light YY.

[0200] It is preferable that the +X side end face of despeckle light-collecting element 205 made of metasurface element 251 abuts against the -X side end face of despeckle light-collecting element 207 made of metasurface element 261. It is also possible to arrange despeckle light-collecting elements 205, 207 with a slight gap in the X direction. A slight gap means a gap so short that it can be considered that the +X side end face of despeckle light-collecting element 205 and the -X side end face of despeckle light-collecting element 207 are both arranged at position PS3, which will be described later, in the X direction.

[0201] In the fourth embodiment and each of the modified examples, the thickness of the metasurface elements 251 and 261, i.e., the size in the X direction, can be reduced to a wavelength order, thereby achieving ultra-thinness. Therefore, each of the metasurface elements 251 and 261 can be arranged in a concentrated manner at a position PS3 conjugate to the position PS4. Another modified example is a configuration in which three or more metasurface elements are arranged side by side with their thickness directions parallel to the X direction, and each metasurface element has a different optical function at a different wavelength. Even with this configuration, multiple metasurface elements can be easily arranged in a concentrated manner at a position conjugate to the image formation region of the light modulation element on the optical path. For example, three metasurface elements may be arranged side by side, with the first metasurface element focusing blue light and despeckling yellow light, the second metasurface element despeckling blue and red light and focusing green light, and the third metasurface element despeckling blue and green light and focusing red light.

[0202] [Fifth embodiment] Next, a fifth embodiment of the present invention will be described with reference to FIGS.

[0203] Although not shown, the projector 102 of the fifth embodiment is obtained by replacing the white light source module 1W of the projector 102 of the fourth embodiment with a white light source module 1W1 shown in FIG.

[0204] (light source module) Fig. 20 is a schematic configuration diagram of a white light source module 1W1 of the fifth embodiment. As shown in Fig. 20, the white light source module 1W1 includes a light source unit 10, a condenser lens 21, a fluorescence rotating element 130, a pickup optical system 40, despeckle condensing elements 205 and 207, a despeckle wavelength filter 210, a second lens array 60, a polarization conversion element 70, and superimposing lenses 81 and 82. In the white light source module 1W1, the above-mentioned components are arranged in the order shown from the -X side to the +X side along the X direction.

[0205] The despeckle wavelength filter 210 is disposed adjacent to the despeckle condensing element 207 on the +X side of the despeckle condensing element 207. The blue laser light DB and yellow light DY emitted from the despeckle condensing element 207 to the +X side in the X direction are incident on the despeckle wavelength filter 210.

[0206] The despeckle wavelength filter 210 includes a metasurface element 281. The metasurface element 281 suppresses the intensity of the blue laser light DB emitted from the despeckle focusing element 207 and adjusts the spectral distribution of the white light LW obtained by combining the blue laser light DB and the yellow light DY. That is, the metasurface element 281 acts as a wavelength filter for the incident blue laser light DB and does not act on the incident yellow light DY. The configuration of the metasurface element 281 will be described later.

[0207] The despeckle wavelength filter 210 emits the blue laser light DB with reduced light intensity and the despeckled yellow light DY along the X direction to the +X side, and makes them incident on the second lens array 60.

[0208] (Despeckle wavelength filter) Fig. 21 is a side view showing the state when blue laser light DB is incident on the metasurface element 281 of the fifth embodiment. As shown in Fig. 21, the metasurface element 281 includes a substrate (base material) 202 having plate surfaces 202a and 202b parallel to the YZ plane, and a plurality of microstructures 208 provided on the plate surface 202b.

[0209] The microstructure 208 has a width d3 in a direction parallel to the plate surface 202b and a height t5 in the X direction (direction intersecting the reference plane) perpendicular to the plate surface 202b. The widths d2 and heights t4 of the multiple microstructures 204 and the intervals p3 between the microstructures 204 may be equal to or different from one another.

[0210] Metasurface element 281 reduces the transmitted light intensity of blue laser light DB while randomly modulating the phase of blue laser light DB that has been despeckled by despeckle condensing element 205 and is being condensed by despeckle condensing element 207 for each position within the region of metasurface element 281 in the YZ plane. Blue laser light DB incident on metasurface element 281 resonates in accordance with multiple microstructures 208 and more strongly than microstructures 204 and 206. Due to a strong light confinement effect caused by this resonance, the transmitted light intensity of blue laser light DB is lower than that of metasurface element 211 and metasurface elements 251 and 261.

[0211] As shown in FIG. 21, the equiphase surface WF B3 are distributed parallel to the YZ plane, and multiple equiphase surfaces WF B3 Assuming that the phases are distributed at equal intervals in the X direction, the phase planes WF of the blue laser light DB transmitted through the metasurface element 281 are B4 is the equiphase surface WF B3 Multiple equiphase surfaces WF B4 Such multiple equal phase surfaces WF B4 The light intensity of the blue laser light DB consisting of the blue laser light DB is reduced. As a result, the despeckle wavelength filter 210 consisting of the metasurface element 281 randomly modulates the phase of the incident blue laser light DB, reduces the transmitted light intensity of the blue laser light DB, and emits it to the +X side in the X direction toward the second lens array 60 shown in FIG.

[0212] The width d3 and height t5 of the microstructure 208 of the metasurface element 281, and the interval p3 between the microstructures 204 are determined to be a suitable phase modulation amount φ in accordance with the peak wavelength of the blue laser light B, so that the blue laser light B passing through the microstructure 208 is randomly phase-modulated as described above, the optical confinement effect of the blue laser light DB is increased, and the transmitted light intensity is reduced. BIn addition, the width d3 and height t5 of the microstructure 208 of the metasurface element 281 and the spacing p3 between the microstructures 204 are set according to the peak wavelength of the yellow light YY and so as not to affect the yellow light YY passing through the microstructure 208.

[0213] 22 is a schematic diagram of the spectral distribution of the blue laser DB and yellow light DY incident on the metasurface element 281. FIG. 23 is a schematic diagram of the spectral distribution of the blue laser DB and yellow light DY emitted from the metasurface element 281. As shown in FIGS. 22 and 23, the blue wavelength λ B The peak of the spectral distribution of the blue laser light DB having a wavelength λ is lowered by a much stronger resonance phenomenon in the microstructure 208 for the blue laser light DB than for the yellow light YY. G and red wavelength λ R Yellow wavelength λ Y The spectral distribution of the yellow light DY having the band is slightly reduced overall due to the resonance phenomenon in the microstructure 208 for the yellow light DY, but remains approximately the same as when it was incident.

[0214] It is preferable that the predetermined values ​​of the width d3, height t5 and spacing p3 of the microstructure 208 of the metasurface element 281 are set taking into consideration the dimensions that can be produced and processed with high precision and low yield using the material of the microstructure 208 in an apparatus used to manufacture the metasurface element 281 based on methods such as RIE, FIB and nanoimprint lithography, without excessively exceeding these dimensions.

[0215] In the metasurface element 281, it is preferable that the material of the microstructure 208 has a high refractive index at least for the blue laser light DB and the yellow light DY and has little absorption. By using a material of the microstructure 208 that has a high refractive index for the blue laser light DB and the yellow light DY, the phase modulation amount φ that can be obtained for a certain height t5 is B , φ YThis increases the degree of freedom in designing the microstructure 208. As the material for the microstructure 208, TiO2, SiN, etc., which have low absorption of light in the visible wavelength range, are preferable.

[0216] In the metasurface element 281, as in the fourth embodiment, completely different functions are realized using two lights of different wavelength bands, blue laser light DB and yellow light DY. Therefore, the behavior when blue laser light B and yellow light YY are incident on each of the metasurface elements 281 in which the width d3 and height t5 of the microstructures 208 and the spacing p3 between the microstructures 208 are set as described above is analyzed using electromagnetic wave analysis such as the FDTD method.

[0217] The metasurface element 281 of the fifth embodiment described above comprises a substrate 202 and at least one microstructure 208 arranged on the plate surface 202b of the substrate 202. The metasurface element 281 of the fifth embodiment has the same action and effect as the metasurface element 211 of the first embodiment with respect to the content common to the metasurface element 211.

[0218] Furthermore, in the metasurface element 281 of the fifth embodiment, the height t5 and width d3 of the microstructure 208 are determined so that the yellow light (light) DY passing through the microstructure 208 is not phase-modulated, and the light intensity of the blue laser light DB passing through the microstructure 208 is reduced when it is emitted compared to when it is incident. The blue laser light DB has green and red wavelengths different from the blue wavelength of the blue laser light DB compared to the yellow light DY, and is an example of "light having a second wavelength different from the first wavelength" in the claims described below. The metasurface element 281 of the fifth embodiment emits the blue laser light DB, which has been despeckled and focused and has reduced light intensity, and the focused yellow light DY toward the microlenses 61 of the second lens array 60.

[0219] According to the metasurface element 281 of the fifth embodiment, the microstructure 206 has a common absolute dimension for the blue laser light DB and the yellow light DY having different wavelengths, and the phase modulation amount φ B , φ Y can be obtained. Furthermore, according to the metasurface element 281 of the fifth embodiment, it is possible to obtain an amount of attenuation of the light intensity due to the resonance phenomenon of the blue laser light DB that corresponds to at least one of the height t5 and width d3 of the microstructure 206. According to each of the metasurface elements 281 of the fifth embodiment, by using the above-mentioned characteristics, a single element can exhibit a despeckle function for one of the blue laser light DB and the yellow light DY, which have mutually different wavelengths, and can reduce the light intensity of the other light, the blue laser light DB and the yellow light DY, at the time of emission compared to the time of incidence, thereby exhibiting some despeckle function for the other light.

[0220] In the metasurface element 281 of the fifth embodiment, for example, the blue wavelength λ B This single element can function as a wavelength filter that reduces the transmitted light intensity (light intensity) of light in a specific wavelength band, such as blue laser light DB, while barely reducing the transmitted light intensity of light in other wavelength bands, such as yellow light DY. Therefore, the light intensity of blue laser light DB, which has a higher light intensity than yellow light DY resulting from yellow light YY generated by the principle of fluorescence, can be suppressed, thereby achieving a balance between blue laser light DB and yellow light DY, as well as a color balance of white light LW. The metasurface element 281 of the fifth embodiment allows for easy design of ultra-thin, compact elements with different optical functions at different wavelengths.

[0221] According to the projector 102 of the fifth embodiment, the white light source module 1W1 is provided with an ultra-thin and compact despeckle wavelength filter 210 made up of a metasurface element 281, which makes it possible to effectively take measures to despeckle the light LL projected onto the screen SCR while preventing the white light source module 1W1 from becoming larger. In particular, when the projector 102 is made smaller and lighter, the space available for placing the despeckle condensing elements 205 and 206 in the white light source module 1W1 is extremely limited. Even in such cases, a despeckle element, condensing element, and wavelength filter made up of a plurality of metasurface elements 251, 261, and 281 can be easily placed at position PS3 where the despeckle effect of the white light source module 1W1 is most pronounced, or at other desired positions.

[0222] Furthermore, in the metasurface element 281 of the fifth embodiment, the microstructures 208 are provided only on the plate surface 202b of the substrate 202, but they may also be provided, for example, only on the plate surface 202a.

[0223] <First Modification and Second Modification> Although not shown, in the metasurface element 281 of the fifth embodiment, an oscillator 402 may be provided at any position on the substrate 202, similar to the second modified example of the third embodiment.

[0224] Also, although not shown, in the metasurface element 281 of the fifth embodiment, as in the third modified example of the third embodiment, the microstructure 208 of the metasurface element 281 may be formed from a material that transmits blue laser light B and yellow light YY and changes volume by shrinking or expanding with temperature changes, or a material that changes phase to either an amorphous or crystalline state.

[0225] In the metasurface element 281 according to the modification of the fifth embodiment described above, the phase modulation amount φ of the blue laser light DB passing through the microstructure 208 Bcan be changed over time, thereby changing the phase modulation pattern for the blue light DB over time. Therefore, according to the metasurface element 281 of the modified example of the fifth embodiment, it is possible to enhance the randomness of the phase modulation pattern for the blue light DB and the despeckle effect.

[0226] Furthermore, since the thickness, i.e., the size in the X direction, of the metasurface elements 251, 261, and 281 of the fifth embodiment and each modified example can be made ultra-thin by keeping it within the wavelength order, each of the metasurface elements 251, 261, and 281 can be arranged in a concentrated manner at position PS3, which is essentially conjugate to position PS4. The metasurface elements 251, 261, and 281 of the fifth embodiment and each modified example correspond to a configuration example in which three or more metasurface elements described in the fourth embodiment are arranged side by side.

[0227] Furthermore, the metasurface element 281 of the modified example of the fifth embodiment may be arranged on the −X side of and adjacent to the despeckle element 201 of, for example, any one or two of the third light source modules 1B, 1G, and 1R of the first embodiment, where light emitted from the light source unit 10 is emitted with a higher light intensity than the other light source modules. For example, by arranging the despeckle wavelength filter 210 made of the metasurface element 281 on the −X side of and adjacent to the despeckle element 201 of the third light source module 1B for blue, the light intensity of the blue laser light DB emitted from the third light source module 1B can be reduced below the green laser light and red laser light emitted from each of the second light source modules 1G and 1R.

[0228] [Sixth embodiment] Next, a sixth embodiment of the present invention will be described with reference to FIG.

[0229] Although not shown, the projector 100 of the sixth embodiment is obtained by replacing the third light source module 1B of the projector 100 of the first embodiment with a third light source module 1B1, which will be described next.

[0230] Although not shown, the third light source module 1B1 of the sixth embodiment includes a light source unit 10, a condenser lens 21, a diffusion element 30, a pickup optical system 40, a despeckle element 209, a reflecting mirror, a first lens array 50, a second lens array 60, a polarization conversion element 70, superimposing lenses 81 and 82, a field lens 90B, and a light modulation element 95B. However, in the third light source module 1B1 of the sixth embodiment, the blue laser light B emitted from the pickup optical system 40 is collimated before entering the first lens array 50. The despeckle element 209 and the first lens array 50 are arranged spaced apart from each other on the optical paths of the blue laser light B and DB. An optical axis AX1 from the light source unit 10 to the despeckle element 209 is aligned along the Z direction. That is, the optical paths of the blue laser light B and DB are refracted from the Z direction to the X direction between the despeckle element 209 and the first lens array 50.

[0231] The despeckle element 201 of the first embodiment is composed of a transmission type metasurface element 211, whereas the despeckle element 209 of the sixth embodiment is composed of a reflection type metasurface element 291. The metasurface element 291 will be described next.

[0232] (Despeckle element) Fig. 24 is a side view of a metasurface element 291 of the sixth embodiment. As shown in Fig. 24, the metasurface element 291 includes a substrate (base material) 202 having plate surfaces 202a and 202b parallel to an XY plane including the X and Y directions, a plurality of microstructures 204 provided on the plate surface 202a, and a reflective film 220 provided on the plate surface 202b. The metasurface element 291 has the same configuration as the metasurface element 211 and is designed in the same way as the metasurface element 211, except that the plate surfaces 202a and 202b are parallel to the XY plane and the reflective film 220 is provided on the plate surface 202b.

[0233] The reflective film 220 is configured to be able to reflect at least the blue laser light B, and is configured, for example, of a metal reflective film made of aluminum (Al) or the like, or a dielectric multilayer film designed according to the peak wavelength of the blue laser light B.

[0234] The metasurface element 291 of the sixth embodiment described above comprises a substrate 202 and at least one microstructure 204 arranged on the plate surface 202b of the substrate 202. The metasurface element 291 of the sixth embodiment has the same effects as the metasurface element 211 of the first embodiment with respect to the contents common to the metasurface element 211.

[0235] Moreover, in the metasurface element 291 of the sixth embodiment, a reflective film 220 is provided on the plate surface 202b opposite to the plate surface 202a of the substrate 202 (the surface opposite to the reference plane). As a result, blue laser light B incident on the metasurface element 291 from the +Z side along the Z direction passes through the microstructure 204 and the substrate 202 in order to be despeckled, and is then reflected by the reflective film 220, and passes through the substrate 202 and the microstructure 204 in order to be further despeckled. Therefore, according to the metasurface element 291 of the sixth embodiment, the phase modulation amount φ which depends on the height t1 is smaller than that of the metasurface element 211 in which the reflective film 220 is not formed on the plate surface 202b of the substrate 202. B That is, the range of the phase modulation amount φ realized by the plurality of microstructures 204 of the metasurface element 291 can be expanded. B The phase modulation amount is twice that of (2×φ B ) can be realized.

[0236] According to the metasurface element 291 of the sixth embodiment, the height t1 of the microstructure 204 formed on the plate surface 202a of the substrate 202 is set to the phase modulation amount φ required for the metasurface element 291. B Specifically, the phase modulation amount φ required for the metasurface element 291 is B Half of (φ B / 2), which makes it possible to reduce the difficulty of fabricating the metasurface element 291 of the sixth embodiment to be lower than the difficulty of fabricating the metasurface element 211 of the first embodiment.

[0237] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as set forth in the claims. Furthermore, the components of multiple embodiments can be combined as appropriate.

[0238] For example, the metasurface element of the present invention, including the metasurfaces of the above-mentioned embodiments and their modified examples, can be appropriately positioned in a position where the despeckle effect is effectively achieved in the image forming region of the light modulation element that forms image light in the light source module, or in a suitable position according to the function realized by the metasurface element. For example, the metasurface element of the present invention, which has only the function of despeckling blue laser light B, may be positioned in the region near the light source unit 10 of the above-mentioned third light source module 1B or white light source module 1W, at position PS1 further forward than the front microlens 14 in the direction of propagation of the blue laser light B in the light source unit 10, or at position PS2 approximately equivalent to the second lens array 60 on the optical path of the blue laser light B.

[0239] Furthermore, the metasurface element of the present invention, including the metasurfaces of the above-mentioned embodiments and their variations, is not limited to projectors and can be applied to any image processing device as long as it has an image forming area where an image on a screen that is focused on the observer's retina is formed.

[0240] The projector according to an aspect of the present invention may have the following configuration. A projector according to one embodiment of the present invention comprises a light source, a metasurface element that modulates the phase of light emitted from the light source, and a light modulation element that modulates the phase-modulated light emitted from the metasurface element to generate image light.

[0241] In a projector according to one embodiment of the present invention, the metasurface element may be positioned conjugate to the image forming area of ​​the light modulation element.

[0242] In one embodiment of a projector of the present invention, the metasurface element comprises a substrate having a first reference surface, and a microstructure arranged on the first reference surface and having a width in a direction along the first reference surface and a height in a direction intersecting the reference surface, and at least one of the height and width may be set according to the amount of phase modulation of light passing through the microstructure.

[0243] In the projector according to one embodiment of the invention, the substrate may have a second reference surface parallel to the first reference surface, and may include a reflective film disposed on the second reference surface.

[0244] In one embodiment of the projector of the present invention, the substrate has a second reference surface parallel to the first reference surface, and is provided with a microstructure arranged on the second reference surface and having a width in a direction along the second reference surface and a height in a direction intersecting the reference surface, and at least one of the height and width may be set according to the amount of phase modulation of light passing through the microstructure.

[0245] In a projector according to one embodiment of the present invention, the microstructures arranged on the first reference surface and the microstructures arranged on the second reference surface may be aligned with each other in a direction parallel to the first reference surface and the second reference surface.

[0246] In one embodiment of the projector of the present invention, the metasurface element comprises a first metasurface section and a second metasurface section, each of which has a substrate having a first reference surface and a microstructure arranged on the first reference surface and having a width in a direction along the first reference surface and a height in a direction intersecting the reference surface, and at least one of the height and width may be set according to the amount of phase modulation of light passing through the microstructure.

[0247] In the projector according to one aspect of the present invention, at least one of the height and the width may be determined so that the amount of phase modulation of light passing through the microstructure is within the range of 0 to 2π.

[0248] In one embodiment of the projector of the present invention, at least one of the height and width may be determined so that light passing through the microstructure is randomly phase modulated and light having a second wavelength different from the first wavelength possessed by the light passing through the microstructure is concentrated.

[0249] In one embodiment of the projector of the present invention, at least one of the height and width may be determined so that light passing through the microstructure is randomly phase modulated and the light intensity at the time of emission of light having a second wavelength different from the first wavelength possessed by the light passing through the microstructure is reduced compared to the time of incidence.

[0250] In one embodiment of the projector of the present invention, the reference surface is divided into multiple regions along the radial direction, and the maximum phase modulation amount of light passing through a microstructure arranged on the reference surface of a first region that is the radially outer of two regions that are adjacent to each other in the radial direction may be smaller than the maximum phase modulation amount of light passing through a microstructure arranged on the reference surface of a second region that is the radially inner of the two regions.

[0251] In one embodiment of the projector of the present invention, at least one of the height and width of the microstructures arranged on the reference surface in the radially innermost region of the reference surface may be determined so that the phase modulation amount of light passing through the microstructures is within the range of 0 to 2π.

[0252] In the projector according to one aspect of the invention, the microstructure may be made of a material that contracts or expands due to a change in temperature.

[0253] In the projector according to one aspect of the present invention, the microstructure may be made of a material that changes phase between an amorphous state and a crystalline state in response to a change in temperature.

[0254] The projector according to an aspect of the present invention may have the following configuration. A projector according to one aspect of the present invention includes a projection optical system that enlarges image light and projects the image light at a predetermined position. [Explanation of symbols]

[0255] 12...LD light source (light source), 211, 212, 213, 214, 216, 217, 218, 219, 251, 261, 281, 291...metasurface element, 211A...metasurface element (first metasurface section), 211B...metasurface element (second metasurface section), 221, 223, 224...composite metasurface element (metasurface element), 1R...first light source module, 1G...second light source module, 1B, 1B1...third light source module, 1W, 1W1...white light source module, 95B, 95G, 95R...light modulation element, 100, 102...projector.

Claims

1. A light source and A metasurface element that modulates the phase of light emitted from the light source; The light emitted from the metasurface element and having the phase modulated is modulated to generate image light. a light modulation element; Equipped with The metasurface element is a substrate having a first reference surface and a second reference surface parallel to the first reference surface; The first reference plane is disposed on the first reference plane, and the width in the direction along the first reference plane and the width of the first reference plane are a first microstructure having a height in a direction crossing the plane; a reflective film disposed on the second reference surface and perpendicular to the incident direction of the light; and Located at a position conjugate with the image forming area of ​​the light modulation element, At least one of the height and the width of the first microstructure is is set according to the phase modulation amount of the light passing through one microstructure, projector.

2. A light source; A metasurface element that modulates the phase of light emitted from the light source; The light emitted from the metasurface element and having the phase modulated is modulated to generate image light. a light modulation element; Equipped with The metasurface element is a substrate having a first reference surface and a second reference surface parallel to the first reference surface; The first reference plane is disposed on the first reference plane, and the width in the direction along the first reference plane and the width of the first reference plane are a first microstructure having a height in a direction crossing the plane; The second reference plane is disposed on the second reference plane, and the width in the direction along the second reference plane and the second reference plane are a second microstructure having a height in a direction crossing the plane; and Located at a position conjugate with the image forming area of ​​the light modulation element, At least one of the height and the width of the first microstructure is is set according to the phase modulation amount of the light passing through one microstructure, At least one of the height and the width of the second microstructure is 2. The phase modulation amount of the light passing through the microstructure is set according to the phase modulation amount of the light passing through the microstructure. projector.

3. A light source; A metasurface element that modulates the phase of light emitted from the light source; The light emitted from the metasurface element and having the phase modulated is modulated to generate image light. a light modulation element; Equipped with The metasurface element is a first metasurface section and a second metasurface section; Located at a position conjugate with the image forming area of ​​the light modulation element, The first metasurface portion is a first substrate having a first reference surface; The first reference plane is disposed on the first reference plane, and the width in the direction along the first reference plane and the width of the first reference plane are a first microstructure having a height in a direction crossing the plane; and The second metasurface portion is a second substrate having a second reference surface parallel to the first reference surface; The second reference plane is disposed on the second reference plane, and the width in the direction along the second reference plane and the second reference plane are a second microstructure having a height in a direction crossing the plane; and At least one of the height and the width of the first microstructure is is set according to the phase modulation amount of the light passing through one microstructure, At least one of the height and the width of the second microstructure is 2. The phase modulation amount of the light passing through the microstructure is set according to the phase modulation amount of the light passing through the microstructure. projector.

4. The metasurface element includes a plurality of the first microstructures and a plurality of the second microstructures. It has a structure and Each of the plurality of first microstructures arranged on the first reference surface is each of the plurality of second microstructures arranged on a surface, the first reference surface and the second overlap on a linear axis perpendicular to the reference plane, 4. The projector according to claim 2 or 3.

5. The metasurface element has a plurality of the first microstructures, the heights of the plurality of first microscopic structures are uniform at a predetermined value; The projector according to claim 1 .

6. The height of the first microstructure is equal to the height of the second microstructure. The projector according to any one of claims 2 to 4.

7. At least one of the height and the width of the first microstructure is The light passing through the first microstructure is randomly phase modulated, and the first microstructure and a second wavelength different from the first wavelength of the light is collected through the second wavelength collector. It is considered The projector according to claim 1 .

8. At least one of the height and the width of the first microstructure is The light passing through the first microstructure is randomly phase modulated, and the first microstructure The light intensity at the time of emission of light having a second wavelength different from the first wavelength of the light passing through the It is determined that the radiation intensity is reduced compared to the incident radiation intensity. The projector according to claim 1 .

9. The metasurface element is The first reference plane is disposed on the first reference plane, and the width in the direction along the first reference plane and the width of the first reference plane are a third microstructure having a height in a direction crossing the plane; Equipped with The first reference surface is a complex surface including two regions adjacent to each other in the radial direction of the first reference surface. It is divided into several areas, The first microstructure is disposed in a first region that is radially outer of the two regions. And, The third microstructure is disposed in a second region that is radially inner of the two regions. And, The maximum phase modulation amount of the light passing through the first microstructure is is smaller than the maximum phase modulation amount of the light, The projector according to claim 1 .

10. At least one of the height and width of the first microstructure is The amount of phase modulation of the light passing through one microstructure is determined to be within the range of 0 to π. 、 The projector according to claim 9.

11. The first microstructure is made of an optical resin that shrinks or expands with temperature changes. Ru, The projector according to claim 1 .

12. The first microstructure undergoes a phase change to an amorphous state or a crystalline state due to a temperature change. It is made up of materials that The projector according to claim 1 .

13. The height of the first microstructure is 500 nm or less. The projector according to claim 5 .

Images