Optical systems, display devices, projection devices, and lighting devices

Abstract

The optical system of the present invention has a coherent light source and a fixed diffuser plate and a relatively movable diffuser plate that intersect the direction of travel of the light emitted from the coherent light source. The fixed diffuser plate emits incident light in a rectangular shape, and the light diffusion surface of the relatively movable diffuser plate moves relative to the incident light.

Description

Technical Field

[0001] This invention relates to optical systems, display devices, projection devices, and lighting devices.

[0002] This application claims priority based on Japanese Patent Application No. 2020-136940, filed on August 14, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] A diffuser plate disperses incident light in multiple directions. Diffuser plates are used in a variety of applications, such as displays, projectors, and lighting.

[0004] For example, Patent Document 1 discloses a projector that uses laser light emitted from a laser source to display a rectangular image by passing the laser light through a diffuser plate and a light tube. Furthermore, Patent Document 2 discloses a light source device having a plurality of adjacent diffusion zones with different diffusion characteristics, each of which is rotatable about a rotation axis.

[0005] Existing technical documents

[0006] Patent Document 1: Japanese Patent No. 4235769

[0007] Patent Document 2: Japanese Patent No. 6160117

[0008] Technical issues

[0009] In the projector disclosed in Patent Document 1, light diffused in a circular shape by a diffuser plate is incident on a rectangular light tube. Therefore, the projector disclosed in Patent Document 1 causes a loss of light input. Furthermore, in the light source device disclosed in Patent Document 2, the shape of the diffused light is circular due to the rotation of a light diffusion element having a plurality of diffusion regions. Therefore, the light diffusion element disclosed in Patent Document 2 causes a loss of light input.

[0010] The present invention was made in view of the above circumstances, and its object is to provide an optical system, display device, projection device and lighting device that utilize light efficiently. Summary of the Invention

[0011] To address the aforementioned issues, the present invention provides the following means.

[0012] The optical system of the first embodiment of the present invention has a coherent light source and a fixed diffuser plate and a relatively movable diffuser plate that intersect the direction of travel of the light emitted from the coherent light source. The fixed diffuser plate emits incident light in a rectangular shape, and the light diffusion surface of the relatively movable diffuser plate moves relative to the incident light.

[0013] In the optical system of the above embodiment, the fixed diffuser and the relatively movable diffuser can be configured in the order of the fixed diffuser and the relatively movable diffuser in relation to the direction of light travel.

[0014] In the optical system of the above embodiment, the fixed diffuser and the relatively movable diffuser can be configured in the order of the relatively movable diffuser and the fixed diffuser with respect to the direction of light travel.

[0015] In the optical system of the above embodiments, the relatively movable diffuser plate can be a rotating diffuser plate whose rotating surface intersects the direction of light travel and is rotatable.

[0016] In the optical system of the above embodiment, the relatively movable diffuser plate can be randomly configured with convex or concave lenses with random radii of curvature on the diffuser surface.

[0017] In the optical system of the above embodiment, the diffusion angle of the fixed diffuser plate is θ. a The diffusion angle of the relatively moving diffuser plate is θ. b When θ can be satisfied b / θ a ≤0.76.

[0018] In the optical system of the above embodiment, the fixed diffuser plate can be a microlens array in which a plurality of microlenses are configured as a matrix when viewed from above.

[0019] The optical system of the above embodiment also has an integrating lens, which may be located behind the fixed diffuser and the relatively movable diffuser in relation to the direction of light travel.

[0020] The optical system of the above embodiment also includes an integrating lens, which may be located behind the fixed diffuser and the relatively movable diffuser in the direction of light travel. The microlens array has a basic unit region surrounded by a plurality of row dashed lines and a plurality of column dashed lines. The plurality of row dashed lines pass through the average position of the center of each microlens in the column direction and extend in the row direction, with the microlenses arranged in the row direction among the plurality of microlenses. The plurality of column dashed lines pass through the average position of the center of each microlens in the row direction and extend in the column direction, with the microlenses arranged in the column direction among the plurality of microlenses. The ratio of the long side to the short side of the integrating lens is approximately equal to the ratio of the long side to the short side of the basic unit region.

[0021] The display device of the second embodiment of the present invention has the optical system related to the above embodiments.

[0022] The projection device of the third embodiment of the present invention has the optical system related to the above embodiments.

[0023] The lighting device of the fourth embodiment of the present invention has the optical system associated with the above embodiments.

[0024] The optical system described in the above embodiments can improve the efficiency of light utilization. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the optical system related to the first embodiment.

[0026] Figure 2 This is a plan view of the fixed diffuser plate related to the first embodiment.

[0027] Figure 3 This is a cross-sectional view of the fixed diffuser plate related to the first embodiment.

[0028] Figure 4 This is a cross-sectional view illustrating an example of a method for manufacturing a fixed diffuser plate.

[0029] Figure 5 This is a cross-sectional view illustrating an example of a method for manufacturing a fixed diffuser plate.

[0030] Figure 6 This is a schematic diagram illustrating the definition of the diffusion angle for a fixed diffuser plate and a rotating diffuser plate.

[0031] Figure 7 This is a schematic diagram of the optical system associated with the first variant.

[0032] Figure 8 A schematic diagram of a display device related to the first applicable example.

[0033] Figure 9 This is a schematic diagram of the evaluation apparatus for the embodiments and comparative examples.

[0034] Figure 10 This is a schematic diagram illustrating the evaluation method for diffused light.

[0035] Figure 11 A graph summarizing the results of the embodiments and comparative examples.

[0036] Symbol Explanation

[0037] 10, 10B, 10G, 10R: Coherent light sources

[0038] 20: Fixed diffuser plate

[0039] 21: Microlenses

[0040] 30: Rotating diffuser plate

[0041] 40: Integrating Lens

[0042] 100, 101: Optical System

[0043] DP: Display device

[0044] Vc: dashed line

[0045] Vr: Dashed line

[0046] θ、θ a θ b Diffusion angle Detailed Implementation

[0047] The technical solutions in the embodiments of the present invention will now be clearly and completely described with appropriate reference to the accompanying drawings. In the description of the present invention, it should be understood that, in order to facilitate understanding of the features, some feature portions are shown enlarged in the accompanying drawings used in the following description, and the size proportions of the constituent elements may differ from the actual dimensions. The materials, dimensions, etc., illustrated in the following description are only some embodiments of the present invention, not all embodiments, and the present invention is not limited thereto. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of the present invention.

[0048] Figure 1 This is a schematic diagram of the optical system 100 related to the first embodiment. The optical system 100 includes coherent light sources 10B, 10G, and 10R, as well as a fixed diffuser plate 20, a rotating diffuser plate (relatively moving diffuser plate) 30, and an integrating lens 40. In addition, Figure 1 The optical system 100 shown has a dichroic mirror DM.

[0049] First, define the directions. Take the flat surface of the fixed diffuser plate 20 as the xy plane, any direction within the xy plane as the x-direction, and the direction orthogonal to the x-direction as the y-direction. The x-direction is an example of a row direction. The y-direction is an example of a column direction. And the direction orthogonal to the xy plane of the fixed diffuser plate 20 is defined as the z-direction.

[0050] Coherent light sources 10B, 10G, and 10R emit coherent light. Examples of coherent light sources 10B, 10G, and 10R are lasers. Figure 1 The coherent light source 10B shown is a blue laser, the coherent light source 10G is a green laser, and the coherent light source 10R is a red laser. The coherent light sources can be preset to various colors, or yellow, green, and red can be produced by irradiating a phosphor with a blue laser. Figure 1 By using a dichroic mirror (DM), various colors emitted from coherent light sources 10B, 10G, and 10R are converged to achieve white.

[0051] Coherent light produces speckle noise. Speckle noise is a random, fine interference pattern that exists as noise, generated by the interference between the diffusion within the illuminated object (e.g., a screen) and the coherent laser beam. Speckle noise can cause a significant deterioration in image quality, for example. When speckle noise occurs, individual colors become brighter and cannot be rendered as white.

[0052] Light from coherent light sources 10B, 10G, and 10R is incident on a fixed diffuser 20 and a rotating diffuser 30. Spot noise is reduced by propagating coherent light through the fixed diffuser 20 and the rotating diffuser 30. Figure 1 The optical system 100 shown can be configured in the order of fixed diffuser 20 and rotating diffuser 30 for the direction of light propagation.

[0053] The fixed diffuser plate 20 is a rectangular diffuser plate that diffuses incident light in a rectangular shape. Diffusing incident light in a rectangular shape means that the ratio of the 10% angular amplitude in the x-direction to the 10% angular amplitude in the xy-direction of the diffused light is less than 1 (10% angular amplitude in the x-direction / 10% angular amplitude in the xy-direction of the diffused light < 1.0). The 10% angular amplitude of the diffused light refers to the angular range where the intensity distribution, after fitting a Gaussian function, is at least 10% of the maximum intensity in the fitted curve.

[0054] The fixed diffuser plate 20 is, for example, a microlens array. Figure 2 This is a plan view of the fixed diffuser plate 20 related to the first embodiment. Figure 3 This is a cross-sectional view of the fixed diffuser plate 20 related to the first embodiment. Figure 3 It is along Figure 2 The dashed line Vc in the middle represents the section cut off by the fixed diffuser plate 20.

[0055] When the fixed diffuser plate 20 is viewed from above in the z-direction, a plurality of microlenses 21 are arranged in a matrix. Each microlens 21 is, for example, approximately rectangular. The plurality of microlenses 21 are arranged according to a basic pattern.

[0056] The basic pattern is a pattern of basic unit regions aligned in the x and y directions, surrounded by row dashed lines Vc and column dashed lines Vr. The row dashed lines Vc are a plurality of dashed lines extending in the x direction, passing through the average position in the column direction (y direction) of the centers of the individual microlenses 21 arranged in the row direction (x direction). The column dashed lines Vr are a plurality of dashed lines extending in the y direction, passing through the average position in the row direction (x direction) of the centers of the individual microlenses 21 arranged in the column direction (y direction).

[0057] Specifically, the average position of the center of each microlens 21 arranged in the row direction (x direction) in the column direction (y direction) and the average position of the center of each microlens 21 arranged in the column direction (y direction) in the row direction (x direction) are obtained by observing the microlenses 21 with an optical microscope, determining the column direction (y direction) position of the 10 microlenses 21 arranged in the row direction (x direction) and the row direction (x direction) position of the 10 microlenses 21 arranged in the column direction (y direction), and calculating the average position for each.

[0058] The smallest unit enclosed by two row dashed lines Vc and two column dashed lines Vr is the basic unit region. When the ratio of the length Gx in the x-direction to the length Gy in the y-direction of the basic unit region is substantially consistent with the ratio of the length in the x-direction to the length in the y-direction of the integrating lens 40 described later, the light utilization efficiency of the optical system 100 is significantly improved. "Substantially consistent" means that, based on either value, the deviation is within a 10% numerical range.

[0059] The microlenses 21 in the fixed diffuser plate 20 are closely spaced. That is, there are no non-lens regions between the microlenses 21. Therefore, the space between the microlenses 21 is an edge. When the height and direction of the edge are irregular, the diffraction of the fixed diffuser plate 20 will be suppressed. Adjacent edge lines are preferably not parallel to each other.

[0060] Microlens 21 can be, for example, a concave lens recessed relative to the reference surface Rp of the fixed diffuser plate 20. Alternatively, microlens 21 can be a convex mirror protruding relative to the reference surface Rp. The reference surface Rp is parallel to the xy plane and contacts the most protruding portion of the first surface 20a. The reference surface Rp can be, for example, the substrate surface before it is machined into the recess of the microlens 21 of the fixed diffuser plate 20. Figure 3 Although it is stated that the microlens 21 is only on the first surface 20a of the fixed diffuser plate 20, the microlens 21 may also be on both the first surface 20a and the second surface 20b. The radius of curvature of each microlens 21 may be random.

[0061] The fixed diffuser 20 is made of a material that can transmit light in the incident wavelength range. Examples of materials for the fixed diffuser 20 include optical glass, crystal, sapphire, resin plates, and resin films. Examples of optical glass include quartz glass, borosilicate glass, and clear glass. Examples of resins include polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polycarbonate (PC), and cyclic olefin copolymers (COC). Inorganic materials such as optical glass, crystal, and sapphire have good lightfastness. Quartz and sapphire have good heat dissipation properties.

[0062] The fixed diffuser plate 20 is manufactured through a resist coating process, an exposure and development process, and an etching process. Figure 4 and Figure 5 This is a schematic diagram illustrating an example of a method for manufacturing a fixed diffuser plate 20.

[0063] First, the resist coating process is as follows: Figure 4 As shown in (a), resist R1 is coated onto substrate S. Substrate S is made of the same material as the fixed diffuser plate 20 as described above, since it is processed into the fixed diffuser plate 20. In the etching process described later, a fluorinated etching gas (CF4, SF6, CHF3, etc.) can be used as the etching gas. Al2O3 and alkali metals may react with the fluorinated etching gas to become non-volatile substances. For example, when etching a glass substrate (such as Corning Eagle XG) containing 27% Al2O3 but without alkali metals with a fluorinated etching gas, Al2O3 residues that are difficult to etch remain and form small protrusions on the surface, leading to a decrease in the transmittance of the glass substrate. The alkali content of substrate S is preferably 20% by mass or less, particularly preferably 10% by mass or less. Substrate S is preferably, for example, quartz glass or TEMPAX glass. A well-known resist R1 can be used.

[0064] Next, as Figure 4 As shown in (b), in the exposure process, light L1 is irradiated onto the resist R1 through a grayscale mask Gm, exposing the resist R1. Exposure is performed repeatedly, for example, by moving the grayscale mask while repeatedly exposing. Depending on the positioning accuracy of the stepping, seams with widths of several micrometers may appear between the basic units formed in a single exposure. To avoid this problem, it is preferable to expose adjacent basic units overlapping. When there is a significant overlap between adjacent basic units, multiple exposures can be adjusted to achieve the desired exposure level.

[0065] The grayscale mask Gm is as follows Figure 5 The basic pattern shown is designed as a reference. The basic pattern is equivalent to the pattern formed by the aforementioned row dashed lines Vc and column dashed lines Vr. The grayscale mask Gm is manufactured based on the basic pattern by adjusting the parameters of the spacing Gx and Gy of the row dashed lines RL and column dashed lines CL, the position of the vertex c of each microlens, and the radius of curvature of each microlens. By changing these parameters, the diffraction pattern output from the fixed diffuser plate 20 is suppressed.

[0066] Next, as Figure 4 As shown in (c), the exposed resist pattern is developed during the development process. A portion of the resist R1 is removed by development, resulting in resist R2 with a resist pattern on its surface. The desired resist pattern, identical to that of the microlens array, is then formed on the surface of resist R2.

[0067] Next, as Figure 4As shown in (d), the substrate S is dry-etched using resist R2 in the etching process. Dry etching is performed, for example, using an active gas G. Gas G is, for example, the fluorine-containing etching gas described above. Through dry etching, the microlens array pattern formed on the surface of the resist R2 is transferred to the substrate S. The substrate S becomes a fixed diffusion plate 20 on its first surface where the microlens array is formed.

[0068] The rotating diffuser 30 has a rotating surface that intersects the direction of light travel and is rotatable. By rotating, the light-diffusing surface of the rotating diffuser 30 moves relative to the incident light. The rotating diffuser 30 is an example of a relatively movable diffuser. The rotating diffuser 30 only needs to move its light-diffusing surface relative to the incident light; for example, a vibrating diffuser can be used instead of the rotating diffuser 30.

[0069] The rotating diffuser 30 can be, for example, a frosted diffuser or a microlens diffuser. When the rotating diffuser 30 is not rotating, it can be a rectangular diffuser that diffuses incident light in a rectangular shape, or a circular diffuser that diffuses incident light in a circular shape. Whether the rotating diffuser 30 is used alone, or either a rectangular or circular diffuser is used, the diffused light becomes circular by moving the diffuser surface relative to the incident light.

[0070] The rotating diffuser 30 can, for example, be configured with convex or concave lenses of random radii of curvature on the diffusion surface. Through random radii of curvature and configuration, efficient propagation of coherent light is achieved, reducing the generation of speckle noise.

[0071] The fixed diffuser plate 20 and the rotating diffuser plate 30 may have an anti-reflective film on at least one side. The anti-reflective film is, for example, a laminated film composed of a low-refractive-index layer and a high-refractive-index layer. The low-refractive-index layer is, for example, SiO2, MgF2, or CaF2. The high-refractive-index layer is, for example, Nb2O5, TiO2, Ta2O5, Al2O3, HfO2, or ZrO2. SiO2, Nb2O5, and Ta2O5 have good light resistance and are difficult to degrade even when exposed to high-density light emitted by high-output lasers or the like. Furthermore, the anti-reflective film can be a moth-eye structure with fine bumps and depressions arranged at intervals of hundreds of nanometers.

[0072] The diffusion angle θ of the fixed diffuser plate 20 a and the diffusion angle θ of the rotating diffuser plate 30 b Preferably, it satisfies θ b / θ a ≤0.76.

[0073] In addition, θ b / θ a The lower limit value is preferably a value greater than 0. Furthermore, it is more preferably a value that satisfies θ. b / θ a≤0.2.

[0074] Figure 6 This is a schematic diagram illustrating the definition of the diffusion angle of the fixed diffuser 20 and the rotating diffuser 30. The diffusion angle θ of the diffuser is obtained based on the following relationship between the average radius of curvature R of the lens, the refractive index n of the diffuser, and the average spacing p between adjacent lenses.

[0075] Diffusion angle θ = 2sin -1 {(p(n-1) / 2R)}

[0076] The diffusion angle θ of a diffuser plate can also be defined as the propagation angle of the light rays emitted from the diffuser plate when parallel light is incident.

[0077] Diffusion angle θ a and diffusion angle θ b When the above relationship is satisfied, the light passing through the two diffusers becomes rectangular. As mentioned above, when using the rotating diffuser 30 alone, the transmitted light propagates in a circular shape in principle. However, when two diffusers are used and the above relationship is satisfied, the transmitted light becomes rectangular. The light passing through the diffusers illuminates the integrating lens or image display device. Since these components are quadrilateral, and the diffused light is rectangular, the light utilization efficiency is increased.

[0078] The integrating lens 40 is a lens that improves the uniformity of illumination on the irradiated surface. By allowing light to pass through the integrating lens 40, the accuracy of the projected image is improved. The integrating lens 40 is located behind the fixed diffuser 20 and the rotating diffuser 30, relative to the direction of light travel.

[0079] When the ratio of the length in the x-direction to the length in the y-direction of the integrating lens 40 is basically the same as the ratio of the length in the x-direction Gx to the length in the y-direction Gy of the basic unit region, the light utilization efficiency of the optical system 100 is significantly improved.

[0080] When using the optical system associated with this embodiment, the light utilization efficiency is higher compared to using a circular diffuser to make the diffused light circular when the fixed diffuser 20 is fixed. Furthermore, the diffusion angle θ of the fixed diffuser 20 is... a The diffusion angle θ with the rotating diffuser plate 30 b The two diffusers satisfy a certain relationship, so that the light rays passing through the two diffusers are approximately rectangular, thereby further improving the light utilization efficiency.

[0081] The above is a detailed description of the first embodiment, but it is not limited to this embodiment. The essence of various modifications and variations is included within the scope of the claims of this invention.

[0082] Figure 7This is a schematic diagram of the optical system 101 related to the first modification. The optical system 101 related to the first modification differs from the optical system 100 described above, and is arranged in the order of fixed diffuser plate 20 and rotating diffuser plate 30. In the optical system 101 related to the first modification, the component symbols that are the same as those in the optical system 100 are omitted from the description.

[0083] Figure 7 The optical system 101 shown is arranged in the order of rotating diffuser 30, fixed diffuser 20, and integrating lens 40 for the direction of light propagation. Even if the arrangement order of the rotating diffuser 30 and the fixed diffuser 20 is reversed, the light passing through the two diffusers is the same. Therefore, the optical system 101 associated with the first modification can also achieve the same effect as the optical system 100 described above.

[0084] The optical systems 100 and 101 described above can be used in display devices, projection devices, lighting devices, etc.

[0085] Figure 8 This is a schematic diagram of a display device DP related to the first applicable example. The display device DP is, for example, a laser television or a DLP projector. The display device DP includes a coherent light source 10B, a fixed diffuser plate 20, a plurality of mirrors M, a phosphor wheel PW, a rotating diffuser plate 30, an integrating lens 40, a plurality of lenses L, a digital microdevice DLD, and a prism TIR.

[0086] Blue light is emitted from the coherent light source 10B. After passing through the fixed diffuser 20 and the phosphor wheel PW, the light enters the rotating diffuser 30. The phosphor wheel PW is irradiated by the blue laser, producing yellow (green, red) light, which then reaches the rotating diffuser 30. The light passing through the rotating diffuser 30 converges at the integrating lens 40 and multiple lenses L. The converged light then passes through the prism TIR and is directed to the digital microdevice DLD. The digital microdevice DLD controls the ON / OFF of the light and outputs the light externally through the prism TIR.

[0087] Example

[0088] In the following Examples 1-15 and Comparative Examples 1-20, designs were made Figure 9 The optical system shown was evaluated through simulation. The optical system comprises a coherent light source 10, a fixed diffuser 20, a rotating diffuser 30, and a screen Sc. The coherent light source 10 outputs light with an intensity of 1 W and a focal spot diameter of 0.6 mm. The distance between the fixed diffuser 20 and the rotating diffuser 30 is 0.5 mm. The distance between the rotating diffuser 30 and the screen Sc is 200 mm. The simulation was performed using Zemax's OpticStudio.

[0089] The total screen area is 40mm × 40mm, and the evaluation area is an 18.5mm × 18.5mm region at the center of the total area. Then, the light utilization efficiency of the evaluation area relative to the total area, as well as the diffusion characteristics in the x and xy directions, are calculated. The xy directions are those tilted at 45° relative to the x and y directions, respectively. Figure 10 This is a schematic diagram illustrating the diffused light in the embodiments and comparative examples. The diffusion characteristics in the x and xy directions are evaluated using 10% angular amplitudes of the diffused light in the x and xy directions. As described above, a 10% angular amplitude refers to the angular range where the intensity distribution is fitted with a Gaussian function, and the intensity is greater than 10% of the maximum intensity in the fitted curve.

[0090] [Examples 1-4, Comparative Examples 1-6]

[0091] In Examples 1-4, the fixed diffuser 20 is a rectangular diffuser that diffuses the incident light in a rectangular shape, and the rotating diffuser 30 is a circular diffuser that diffuses the incident light in a circular shape. In Comparative Examples 1-6, the fixed diffuser 20 is a circular diffuser, and the rotating diffuser 30 is a circular diffuser. In Examples 1-4 and Comparative Examples 1-6, the detection intensity of the total area is 1425 mW. In Examples 1-4, the diffusion angle θ of the fixed diffuser 20 is... a The diffusion angle θ of the fixed diffuser plate 20 was set to 5° in Comparative Examples 1 to 6. a Set it to 7°. Then, change the diffusion angle θ of the rotating diffuser plate 30. b Each case was evaluated. The results are summarized in Table 1 below.

[0092] [Table 1]

[0093]

[0094] Examples 1-4 demonstrate higher light utilization efficiency compared to Comparative Examples 1-6. Furthermore, when the diffusion angle θ... b / Diffusion angle θ a When the value is less than 0.8, the shape of the diffused light is approximately rectangular.

[0095] [Examples 5-8, Comparative Examples 7-13]

[0096] In Examples 5-8, the fixed diffuser plate 20 is a rectangular diffuser plate, and the rotating diffuser plate 30 is a circular diffuser plate. In Comparative Examples 7-13, the fixed diffuser plate 20 is a circular diffuser plate, and the rotating diffuser plate 30 is a circular diffuser plate. In Examples 5-8 and Comparative Examples 7-13, the detection intensity of the total area is around 300 mW. In Examples 5-8, the diffusion angle θ of the fixed diffuser plate 20 is... a The diffusion angle θ of the fixed diffuser plate 20 was set to 10° in Comparative Examples 7-13. aSet it to 14°. Then change the diffusion angle θ of the rotating diffuser plate 30. b Each case was evaluated. The results are summarized in Table 2 below.

[0097] [Table 2]

[0098]

[0099] Examples 5-8 demonstrate higher light utilization efficiency compared to Comparative Examples 7-13. Furthermore, when the diffusion angle θ... b / Diffusion angle θ a When the value is less than 0.8, the shape of the diffused light is approximately rectangular.

[0100] [Examples 9-15, Comparative Examples 14-20]

[0101] In Examples 9-15, the fixed diffuser plate 20 is a rectangular diffuser plate, and the rotating diffuser plate 30 is a circular diffuser plate. In Comparative Examples 14-20, the fixed diffuser plate 20 is a circular diffuser plate, and the rotating diffuser plate 30 is a circular diffuser plate. In Examples 9-15 and Comparative Examples 14-20, the detection intensity of the total area is around 100 mW. In Examples 9-15, the diffusion angle θ of the fixed diffuser plate 20 is... a The diffusion angle θ of the fixed diffuser plate 20 was set to 16° in Comparative Examples 14-20. a Set it to 22°. Then change the diffusion angle θ of the rotating diffuser plate 30. b Each case was evaluated. The results are summarized in Table 3 below.

[0102] [Table 3]

[0103]

[0104] Examples 9-15 exhibit higher light utilization efficiency compared to Comparative Examples 14-20. Furthermore, when the diffusion angle θ... b / Diffusion angle θ a When the value is less than 0.8, the shape of the diffused light is approximately rectangular.

[0105] Furthermore, the results of the above embodiments and comparative examples are summarized in Figure 11 .like Figure 11 As shown, if the diffusion angle θ b / Diffusion angle θ a The value is below 0.76, indicating a higher light utilization efficiency compared to the maximum light utilization efficiency in the comparative example.

[0106] As will be apparent from the disclosure described herein, the embodiments herein can be modified in various ways. Such modifications should not be considered a departure from the spirit and scope of this disclosure, and it will be apparent to those skilled in the art that all such modifications are intended to be included within the scope of the claims.

Claims

1. An optical system comprising a coherent light source, a fixed diffuser plate intersecting the direction of travel of light rays emitted from the coherent light source, a relatively movable diffuser plate, and an integrating lens, characterized in that, The fixed diffuser emits incident light in a rectangular shape. The light-diffusing surface of the relatively movable diffuser moves relative to the incident light. The fixed diffuser is a microlens array in which a plurality of microlenses are arranged in a matrix when viewed from above. The integrating lens is located behind the fixed diffuser and the relatively movable diffuser in the direction of light travel. The microlens array has a basic unit area surrounded by a plurality of row dashed lines and a plurality of column dashed lines. The plurality of row dashed lines pass through the average position of the center of each microlens in the column direction and extend in the row direction. The microlenses are arranged in the row direction among the plurality of microlenses. The plurality of column dashed lines pass through the average position of the center of each microlens in the row direction and extend in the column direction. The microlenses are arranged in the column direction among the plurality of microlenses. The ratio of the long side to the short side of the integrating lens is approximately equal to the ratio of the long side to the short side of the basic unit area.

2. The optical system as described in claim 1, characterized in that, The fixed diffuser plate and the relatively movable diffuser plate are arranged in the order of the fixed diffuser plate and the relatively movable diffuser plate in relation to the direction of light travel.

3. The optical system as described in claim 1, characterized in that, The fixed diffuser plate and the relatively movable diffuser plate are arranged in the order of the relatively movable diffuser plate and the fixed diffuser plate, with respect to the direction of light travel.

4. The optical system as described in any one of claims 1 to 3, characterized in that, The relatively movable diffuser plate is a rotating diffuser plate whose rotating surface intersects the direction of light travel and is rotatable.

5. The optical system as described in any one of claims 1 to 4, characterized in that, The relatively movable diffuser plate has convex or concave lenses with random radii of curvature on the diffuser surface.

6. The optical system as described in any one of claims 1 to 5, characterized in that, When the diffusion angle of the fixed diffuser plate is θa and the diffusion angle of the relatively moving diffuser plate is θb, the condition θb / θa≦0.76 is satisfied.

7. A display device, characterized in that, An optical system having any one of claims 1 to 6.

8. A projection device, characterized in that, An optical system having any one of claims 1 to 6.

9. A lighting device, characterized in that, An optical system having any one of claims 1 to 6.

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