Optical element and light source device

Abstract

The present invention increases the light extraction efficiency of diffused light and reduces light having locally high luminous intensity. An optical element (100) comprises a base material (1) including a first surface (1a) and a second surface (1b) positioned at a side opposite of the first surface. The base material (1) comprises, on at least a portion of the first surface (1a) and the second surface (1b): an optical region (10) in which at least one optical element (11) is disposed; and a peripheral region (12) in which the optical element (11) is not disposed, the peripheral region (12) being provided surrounding the optical region on the surface of the base material on which the optical region is provided. The optical element (11) is a lens element, and if one cross-sectional region of the at least one optical element, the cross-sectional region including the optical axis of the optical element closest to the peripheral region, and extending from the vertex of the optical element through which the optical axis passes to the end closest to the optical element in the peripheral region, is defined as a boundary region (110), the slope of the surface in the boundary region (110) has an average absolute value of 1.00 or less and a variation σ of 0.10 or greater.

Description

Optical element and light source device

[0001] The present disclosure relates to an optical element and a light source device.

[0002] 2. Description of the Related Art Optical elements such as lens arrays that diffuse incident light and emit diffused light are known, and light source devices that include such optical elements are also known.

[0003] For example, Patent Document 1 discloses an optical element having an optical region in which optical elements are arranged on a portion of at least one surface of a flat substrate, and a peripheral region on the surface of the substrate where the optical region is arranged, surrounding the optical region, in which no optical elements are arranged.

[0004] International Publication No. 2022 / 202514

[0005] However, in the optical element described in Patent Document 1, light incident on the boundary region between the optical region and the peripheral region is totally reflected by the optical element, and an amount of light returning to the direction of incidence increases, which may reduce the light extraction efficiency of diffused light emitted from the optical element. Also, in the optical element described in Patent Document 1, light incident on the boundary region between the optical region and the peripheral region may be locally concentrated, which may cause light with locally high luminous intensity to be emitted from the optical element.

[0006] An object of one aspect of the present disclosure is to increase the light extraction efficiency of diffused light and reduce light with locally high luminous intensity.

[0007] An optical element according to one aspect of the present disclosure has a substrate including a first surface and a second surface located opposite the first surface, the substrate including an optical region in which at least one optical element is arranged in a portion of at least one of the first surface and the second surface, and a peripheral region in which the optical element is not arranged, the peripheral region being arranged around the optical region on the surface of the substrate where the optical region is arranged, the optical element being a lens element, and in a cross section including the optical axis of the at least one optical element closest to the peripheral region, the cross-sectional region extending from the vertex of the optical element through which the optical axis passes to the end of the peripheral region closest to the optical element being defined as a boundary region, the average absolute value of the slope of the surface in the boundary region being 1.00 or less and the variation σ being 0.10 or more.

[0008] According to one aspect of the present disclosure, it is possible to increase the light extraction efficiency of diffused light and reduce light with locally high luminous intensity.

[0009] 1. A schematic top view showing the overall configuration of an optical element according to a first embodiment. A schematic cross-sectional view of the optical element taken along line II-II in FIG. 1. A schematic view showing the relationship between the inclination of the surface in the boundary region of the optical element according to the first embodiment and the diffusion angle. A view showing an example of the area ratio between the substrate and the optical region in the optical element according to the first embodiment. A view showing another example of the area ratio between the substrate and the optical region in the optical element according to the first embodiment. A top view photograph showing an optical element according to Example 1. A view showing the cross-sectional shape of the optical element taken along line VII-VII in FIG. 6. An enlarged view of region VIII in FIG. 7. A view showing the first derivative of FIG. 8. A view showing the probability density of the diffusion angle of light incident on region VII in FIG. 7. A top view photograph showing an optical element according to Example 2. A view showing the cross-sectional shape of the optical element taken along line XII-XII in FIG. 11. An enlarged view of region XIII in FIG. 12. A view showing the first derivative of FIG. 13. A view showing the probability density of the diffusion angle of light incident on region XIII in FIG. 12. A perspective view showing the behavior of light incident on the boundary region of an optical element according to Example 3. A side view showing the behavior of light incident on the boundary region of an optical element according to Example 3. 1 is a diagram showing light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 3 at a first-surface incident angle of 10 degrees. FIG. 2 is a diagram showing light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 3 at a first-surface incident angle of 20 degrees. FIG. 3 is a diagram showing light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 3 at a first-surface incident angle of 30 degrees. FIG. 4 is a perspective view showing the behavior of light incident on a boundary region of an optical element according to Example 1. FIG. 5 is a side view showing the behavior of light incident on a boundary region of an optical element according to Example 1. FIG. 6 is a diagram showing diffused light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 1 at a first-surface incident angle of 10 degrees. FIG. 7 is a diagram showing diffused light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 1 at a first-surface incident angle of 20 degrees. FIG. 8 is a diagram showing diffused light irradiated onto an irradiation surface when light is incident on a boundary region of an optical element according to Example 1 at a first-surface incident angle of 30 degrees. FIG. 9 is a schematic perspective view of a light source device according to a second embodiment. 10A and 10B are diagrams illustrating a first example of diffused light emitted from a light source device according to a second embodiment.10A and 10B are diagrams showing a second example of diffused light emitted from the light source device according to the second embodiment; FIG. 10B are diagrams showing a third example of diffused light emitted from the light source device according to the second embodiment; FIG. 10C are diagrams showing a first example of the intensity profile of diffused light emitted from the light source device according to the second embodiment; and FIG. 10D are diagrams showing a second example of the intensity profile of diffused light emitted from the light source device according to the second embodiment.

[0010] Hereinafter, embodiments for carrying out the present disclosure will be described in detail with reference to the drawings. However, the embodiments shown below are merely examples of optical elements for realizing the technical ideas of the present disclosure, and are not limited to the following. Note that the size, positional relationship, etc. of components shown in each drawing may be exaggerated for clarity. In each drawing, the same components are denoted by the same reference numerals, and duplicate explanations will be omitted as appropriate.

[0011] In the drawings shown below, a Cartesian coordinate system having an X-axis, a Y-axis, and a Z-axis may be used to represent directions. The X-direction along the X-axis indicates a predetermined direction within the plane of the first surface of the optical element according to the embodiment. The Y-direction along the Y-axis indicates a direction perpendicular to the X-direction within the plane of the first surface. The Z-direction along the Z-axis indicates a direction perpendicular to the first surface.

[0012] The direction in which the arrow points in the X direction is denoted as the +X direction, and the direction opposite to the +X direction is denoted as the -X direction. The direction in which the arrow points in the Y direction is denoted as the +Y direction, and the direction opposite to the +Y direction is denoted as the -Y direction. The direction in which the arrow points in the Z direction is denoted as the +Z direction, and the direction opposite to the +Z direction is denoted as the -Z direction. In the embodiment, light traveling in the +Z direction is incident on the optical element and emitted from the optical element. In this specification, a top view refers to viewing the optical element according to the embodiment in the direction in which the light travels, i.e., the +Z direction. However, these directional expressions do not limit the directions in the embodiments of the present disclosure.

[0013] In this specification and claims, "substantially parallel" means that the absolute value of the angular deviation from the parallel state is between 0 and 10 degrees, and "substantially perpendicular" means that the absolute value of the angular deviation from the perpendicular state is between 0 and 10 degrees.

[0014] [First Embodiment] <Configuration of Optical Element According to First Embodiment> The overall configuration of an optical element according to a first embodiment will be described with reference to Figures 1 and 2. Figure 1 is a schematic top view showing an example of the overall configuration of an optical element 100 according to the first embodiment. Figure 2 is a schematic cross-sectional view of the optical element 100 taken along line II-II in Figure 1.

[0015] As shown in FIG. 2, the optical element 100 has a substrate 1 including a first surface 1a and a second surface 1b located opposite the first surface 1a. As shown in FIGS. 1 and 2, the substrate 1 includes an optical region 10 in which optical elements 11-1 to 11-4 are arranged in a portion of the first surface 1a. The substrate 1 also includes a peripheral region 12, which is provided around the optical region 10 on the surface of the substrate 1 where the optical region 10 is provided and in which no optical elements 11 are arranged. The optical elements 11 are lens elements. In the example shown in FIG. 2, a first anti-reflection film 13a is provided on each surface of the optical region 10 and the peripheral region 12 on the first surface 1a of the substrate 1. Furthermore, a second anti-reflection film 13b is provided on the surface of the second surface 1b of the substrate 1.

[0016] In FIG. 2, in a cross section including the optical axis 11C-1 of the optical element 11-1 closest to the peripheral region 12 among the optical elements 11-1 to 11-4, the cross-sectional region from the vertex 11T-1 of the optical element 11-1 through which the optical axis 11C-1 passes to the end 12E of the peripheral region 12 closest to the optical element 11-1 is defined as the boundary region 110. In this embodiment, the average absolute value of the surface inclination a in the boundary region 110 is 1.00 or less, and the variation σ is 0.10 or more. σ represents the standard deviation. The optical axis 11C-1 refers to an axis that passes through the center of the optical element 11-1 and is aligned with the direction of light propagation. In the example shown in FIG. 2, the direction of light propagation is along the Z-axis. The vertex 11T-1 and the end 12E are not included in the boundary region 110.

[0017] In the example shown in Fig. 2, the first surface 1a corresponds to the incident surface onto which light is incident, and the second surface 1b corresponds to the exit surface from which light incident from the incident surface is emitted after passing through the inside of the substrate 1. The optical element 100 shown in Fig. 2 diffuses the light incident from the first surface 1a in the optical region 10, and emits diffused light with low directionality from the second surface 1b.

[0018] 1 and 2, optical element 11 is a generic notation when optical elements 11-1 to 11-4 are not distinguished from each other. In the example shown in Figures 1 and 2, the reference numeral for optical element 11 and the reference numerals for optical elements 11-1 to 11-4 are written together to indicate that optical element 11 is a generic notation for optical elements 11-1 to 11-4.

[0019] Here, for example, in the optical element described in Patent Document 1, the boundary region between the optical region and the peripheral region is configured as a plane substantially perpendicular to the second surface on the side from which light is emitted from the optical element. In the optical element described in Patent Document 1, the boundary region is a plane with an infinite inclination, since the boundary region is a plane substantially perpendicular to the second surface. In an optical element including a boundary region with an infinite inclination plane, light incident on the boundary region may be totally reflected by the second surface on the side from which light is emitted after passing through the substrate of the optical element, resulting in an increase in the amount of light returning in the direction of incidence. The increase in returned light may reduce the light extraction efficiency of diffused light emitted from the optical element. Furthermore, in an optical element including a boundary region with an infinite inclination plane, light incident on the boundary region between the optical region and the peripheral region may be locally concentrated, resulting in light with locally high luminous intensity being emitted from the optical element. Light with locally high luminous intensity may be undesirable from the perspective of eye safety, which reduces harm to human eyes.

[0020] In the optical element 100 according to this embodiment, the surface inclination a in the boundary region 110 has an average absolute value of 1.00 or less and a variation σ of 0.10 or more. For example, the surface in the boundary region 110 is a smoothly curved surface that satisfies the conditions of an average absolute value of 1.00 or less and a variation σ of 0.10 or more. By satisfying this condition, the surface inclination a in the boundary region 110 is no longer uniform, and light incident on the boundary region 110 is refracted at various refraction angles. Since the light incident on the boundary region 110 is refracted at various refraction angles, light that passes through the interior of the substrate 1 is incident on the second surface 1b at various angles, thereby reducing the light that is totally reflected at the second surface 1b and reducing the amount of light that returns in the direction of incidence. By reducing the returned light, the light extraction efficiency of the diffused light emitted from the optical element 100 is increased. Furthermore, in the optical element 100, light incident on the boundary region 110 is refracted at various refraction angles, thereby reducing localized concentration of light incident on the boundary region 110 and emitted from the optical element 100, and reducing light with locally high luminous intensity emitted from the optical element 100. As described above, in this embodiment, the light extraction efficiency of diffused light is increased and light with locally high luminous intensity can be reduced. Furthermore, by reducing light with locally high luminous intensity, an optical element 100 with high safety from the perspective of eye safety can be provided. In particular, when light incident on the optical element is light that is prone to high luminous intensity, such as laser light, reducing light with locally high luminous intensity can achieve a significant effect from the perspective of eye safety.

[0021] The average absolute value of the surface inclination a in the boundary region 110 is preferably 0.90 or less, more preferably 0.80 or less, and even more preferably 0.70 or less. From the viewpoint of increasing the diffusion angle γ, the average absolute value of the inclination a is preferably 0.2 or more, and even more preferably 0.3 or more. The variation σ is preferably 0.20 or more, more preferably 0.30 or more, and even more preferably 0.40 or more.

[0022] In the optical element 100, a peripheral region 12 is provided around the optical region 10. This allows a bonding material to be applied to the peripheral region 12 when bonding the optical element 100 to another member, thereby reducing infiltration of a portion of the optical region 10 with the bonding material. By reducing the region that is infiltrated with the bonding material and does not provide the desired optical properties, the optical region 10 can be used effectively.

[0023] Furthermore, by providing the peripheral region 12 around the optical region 10, when a plurality of optical elements 100 are formed on one substrate and the substrate is cut to obtain a large number of the optical elements 100, it is possible to prevent chipping or other defects from occurring in the optical region 10. Preventing chipping or other defects improves the quality of each of the optical elements 100 obtained in large numbers, and also prevents a decrease in the mechanical strength of the optical region 10 due to defects in the optical region 10.

[0024] In the optical element 100 shown in FIGS. 1 and 2 , the optical region 10 is recessed relative to the peripheral region 12 in the substrate 1. The optical element 11 shown in FIGS. 1 and 2 has a concave surface recessed relative to the peripheral region 12. Because the optical region 10 is recessed relative to the peripheral region 12, when the optical element 100 comes into contact with other members, the peripheral region 12 comes into contact with the other members preferentially. This reduces contact of the optical element 11 arranged in the optical region 10 with other members, and reduces damage to the optical element 11 due to contact or friction with other members. However, the optical element 11 is not limited to a concave surface and may be a convex surface. Furthermore, the apex of the convex surface is not limited to being located lower than the peripheral region 12 in the direction along the optical axis 11C-1 and may be located higher.

[0025] 1 and 2 , the optical region 10 includes a plurality of optical elements 11, which are arranged two-dimensionally without exposing any flat surfaces. By not exposing any flat surfaces, the optical element 100 can reduce high-intensity light that passes through the flat surfaces and travels straight. This makes it possible to provide an optical element 100 that is highly safe from the viewpoint of eye safety.

[0026] In the example shown in Figures 1 and 2, the distance Ds connecting the vertices 11T-1 and 11T-2 of adjacent optical elements 11-1 and 11-2 among the multiple optical elements 11 is 10 μm or more and 200 μm or less. By setting the distance Ds to 10 μm or more, it is easier to process the adjacent optical elements 11-1 and 11-2 compared to when the distance Ds is less than 10 μm, which makes it easier to manufacture the optical element 100. Furthermore, by setting the distance Ds to 200 μm or less, the amount of processing required for each of the optical elements 11-1 and 11-2 to connect the end of the optical element 11-1 and the end of the optical element 11-2 can be reduced compared to when the distance Ds is greater than 200 μm. By reducing the amount of processing required for each of the optical elements 11-1 and 11-2, the manufacturing efficiency of the optical element 100 can be improved. Furthermore, by reducing the amount of processing required for each of the optical elements 11-1 and 11-2, the thickness of the optical element 100, i.e., the length of the optical element 100 in the Z direction, can be prevented from becoming thin, and the mechanical strength of the optical element 100 can be increased.

[0027] In the example shown in FIG. 2 , the depth Dp between the vertex 11T-1 of the optical element 11-1 and the end 12E of the peripheral region 12 in the direction along the optical axis 11C-1 is 3 μm or more and 100 μm or less. By setting the depth Dp to 3 μm or more, the optical element 11-1 can be more easily processed compared to when the depth Dp is less than 3 μm, thereby facilitating the manufacture of the optical element 100. Furthermore, by setting the depth Dp to 100 μm or less, the amount of processing of the optical element 11-1 can be reduced compared to when the depth Dp is greater than 100 μm. By reducing the amount of processing of the optical element 11-1, the manufacturing efficiency of the optical element 100 can be improved. Furthermore, by reducing the amount of processing of the optical element 11-1, the thickness of the optical element 100 can be prevented from becoming thin, thereby increasing the mechanical strength of the optical element 100. Note that while the above example describes the optical element 11-1, similar effects can be obtained with other optical elements 11.

[0028] The substrate 1 can be made of a material including a glass material, a resin material, or the like. The glass material or resin material used for the substrate 1 can be selected appropriately depending on the application of the optical element 100. The optical elements 11 can be formed on the substrate 1 by etching, molding, or the like, and disposed in the optical region 10.

[0029] The substrate 1 may include an optical region 10 on at least one of the first surface 1a and the second surface 1b. The optical region 10 is not limited to the four optical elements 11-1 to 11-4, but may include at least one optical element 11. A cross section including the optical axis 11C of the optical element 11-1 closest to the peripheral region 12 may be any cross section of the optical element 100, as long as it includes the optical axis 11C of the optical element 11-1 closest to the peripheral region 12. The incident surface is not limited to the first surface 1a, but may be the second surface 1b. The exit surface is not limited to the second surface 1b, but may be the first surface 1a.

[0030] The first antireflection film 13a reduces light reflected from the first surface 1a of the substrate 1. The second antireflection film 13b reduces light reflected from the second surface 1b of the substrate 1. Each of the first antireflection film 13a and the second antireflection film 13b can be configured to include a dielectric film material such as magnesium fluoride. However, the optical element 100 does not necessarily have to include the first antireflection film 13a and the second antireflection film 13b.

[0031] <Relationship Between the Inclination a of the Surface in the Boundary Region 110 and the Diffusion Angle γ> Figure 3 is a schematic diagram showing an example of the relationship between the inclination a of the surface in the boundary region 110 of the optical element 100 and the diffusion angle γ. Figure 3 is an enlarged view of the optical element 11-1 in Figure 2. In Figure 3, the light L indicated by the thick line represents a light ray incident on the boundary region 110 of the optical element 11-1. In the example shown in Figure 3, the light L incident on the boundary region 110 from a direction perpendicular to a plane parallel to the second surface 1b is refracted at the surface of the boundary region 110, passes through the inside of the base material 1, and then is emitted from the second surface 1b of the optical element 100.

[0032] In the example shown in FIG. 3 , the inclination a represents the inclination of the surface at position Po1 in the boundary region 110 where light L is incident. The inclination angle a' represents the angle of the inclination of the surface at position Po1 in the boundary region 110 with respect to a plane parallel to the second surface 1b. The normal angle θ represents the angle of the normal (-1 / a) to the surface at position Po1 in the boundary region 110 with respect to a plane parallel to the second surface 1b. The refraction angle β represents the angle of light L with respect to the normal (-1 / a) to the surface at position Po1 in the boundary region 110. The second surface incident angle ε represents the angle of light L that enters the interior of the substrate 1 through position Po1, passes through the interior of the substrate 1, and then enters position Po2 on the second surface 1b with respect to the normal to the second surface 1b. The diffusion angle γ represents the angle of light L that exits position Po2 on the second surface 1b with respect to the normal to the second surface 1b.

[0033] The normal angle θ is expressed by the following equation (1).

[0034]

[0035] The refraction angle β is expressed by the following formula (2): where n is the refractive index of the substrate 1, and π is the ratio of the circumference of a circle to its circumference.

[0036]

[0037] The second surface incident angle ε is expressed by the following formula (3).

[0038]

[0039] The diffusion angle γ is expressed by the following equation (4).

[0040]

[0041] Table 1 shows the correspondence between the tilt a, tilt angle a', normal angle θ, refraction angle β, second surface incident angle ε, and diffusion angle γ obtained using the above equations (1) to (4) when the refractive index n of the substrate 1 is 1.52.

[0042]

[0043] When the refractive index n of the substrate 1 is 1.52, the critical angle is 41.14 degrees. Therefore, if the second surface incident angle ε is less than 41.14 degrees, light L that passes through the interior of the substrate 1 and is incident on the second surface 1b is refracted at the second surface 1b and emitted from the second surface 1b. On the other hand, if the second surface incident angle ε is 41.14 degrees or more, light L is totally reflected by the second surface 1b.

[0044] In an optical element 100 in which multiple optical elements 11 are arranged, light incident on an optical element 11 arranged on the first surface 1a may be refracted by the optical element 11 and then incident on an adjacent optical element 11. Considering the case where light incident on an optical element 11 enters an adjacent optical element 11, when the light enters the optical element 11 from a direction perpendicular to a plane parallel to the second surface 1b, it is preferable that the second surface incident angle ε is 27.4 degrees or less and the slope a is 2.0 degrees or less. A slope a of 2.0 degrees or less corresponds to a slope angle a' of 63.4 degrees or less. Furthermore, when considering the case where light enters an adjacent optical element 11, when the light enters the optical element 11 from a direction intersecting a plane parallel to the second surface 1b, it is preferable that the refraction angle β is 36.0 degrees or less. By satisfying the above conditions, the optical element 100 can reduce the amount of returning light caused by total reflection at the second surface 1b and increase the light extraction efficiency of the diffused light emitted from the optical element 100.

[0045] Furthermore, the diffusion angle γ is uniquely determined by the inclination a of the surface in the boundary region 110, regardless of the direction of light incident on the boundary region 110. If the inclination a of the surface in the boundary region 110 is substantially constant regardless of position, the light emitted from the optical element 100 will be locally concentrated, and light with locally high luminous intensity will be more likely to be included in the diffused light. In contrast, in the optical element 100, by changing the inclination a of the surface in the boundary region 110 depending on the position, it is possible to reduce the local concentration of the light emitted from the optical element 100 and reduce light with locally high luminous intensity.

[0046] The optical element 100 preferably has an FWHM of 20 degrees or greater when parallel light having an emission peak wavelength of 300 nm or greater and 1000 nm or less is incident thereon. By satisfying this condition, the diffused light emitted from the optical element 100 can be spread and irradiated onto the irradiation surface. Note that the FWHM (full width at half maximum) refers to the maximum angular region enclosed by an intensity of 0.5 when the average intensity in the diffusion angle range of -10° to +10° is normalized as 1 in the one-dimensional direction in which the distance of a two-dimensional image projected onto a plane parallel to the surface of the element is maximized, and the relative intensity is plotted as a function of the diffusion angle.

[0047] By setting the FWHM to 20 degrees or more when parallel light having an emission peak wavelength of 300 nm or more and 1000 nm or less is incident, the following effects can be obtained when incorporating the optical element 100 into a device: (1) When incorporating the optical element 100 into a projector, the device can be made smaller. (2) When incorporating the optical element 100 into a sensing device, information from a wider field of view can be captured at once. (3) When incorporating the optical element 100 into a lighting device, the illumination range at a short distance can be expanded.

[0048] When parallel light having an emission peak wavelength of 300 nm or more and 1000 nm or less is incident on the optical element 100, the total light transmittance of the diffused light is preferably 93% or more. By satisfying this condition, the diffused light emitted from the optical element 100 can be made brighter.

[0049] When parallel light having an emission peak wavelength of 300 nm or more and 1000 nm or less is incident, the total light transmittance of the diffused light emitted from the optical element 100 is set to 93% or more, thereby reducing the attenuation of light that passes through the optical element 100. This makes it possible to reduce the power consumption of the device when the optical element 100 is incorporated into devices such as projectors and sensing devices. Furthermore, when the optical element 100 is incorporated into a lighting device, it is possible to provide brighter illumination with the same power consumption.

[0050] Next, the area ratio between the substrate 1 and the optical region 10 in the optical element 100 will be described with reference to Fig. 4 and Fig. 5. Fig. 4 is a diagram showing an example of the area ratio between the substrate 1 and the optical region 10 in the optical element 100. Fig. 5 is a diagram showing another example of the area ratio between the substrate 1 and the optical region 10 in the optical element 100.

[0051] In the optical element 100 shown in FIG. 4, the substrate 1 has a substantially rectangular outer edge shape in top view. The optical region 10 also has a substantially rectangular outer edge shape in top view. The width of the substrate 1 in the X direction is b, the width of the optical region 10 in the X direction is b × (1-P), the width of the substrate 1 in the Y direction is c, and the width of the optical region 10 in the Y direction is c(1-Q). Note that P satisfies 0<P<1, and Q satisfies 0<Q<1. In this case, the area ratio of the optical region 10 to the area of ​​the substrate 1 can be expressed as 1-P-Q + P × Q.

[0052] Table 2 shows the correspondence between P, Q, and the area ratio of the optical region 10 to the area of ​​the substrate 1.

[0053]

[0054] In the optical element 100 shown in Fig. 5, the substrate 1 has a substantially circular outer edge shape in top view. The optical zone 10 also has a substantially circular outer edge shape in top view. The radius of the substrate 1 is d, and the radius of the optical zone 10 is d x (1 - R). Note that R satisfies 0 < R < 1. In this case, the ratio of the area of ​​the optical zone 10 to the area of ​​the substrate 1 is 1 - 2 x R + R ２ It can be written as follows.

[0055] Table 3 shows the correspondence between R and the area ratio of the optical region 10 to the area of ​​the substrate 1.

[0056]

[0057] In the optical element 100 shown in each of FIGS. 4 and 5 , the area ratio of the optical region 10 to the area of ​​the substrate 1 is preferably 0.0625 or more and 0.9025 or less. For example, if the area of ​​the optical region 10 is too large relative to the area of ​​the substrate 1, when bonding the optical element 100 to another member, the area on the substrate 1 to which the bonding material is applied becomes narrow, and good bonding strength may not be obtained. In the optical element 100, by setting the area ratio of the optical region 10 to the area of ​​the substrate 1 to 0.9025 or less, good bonding strength may be obtained when bonding the optical element 100 to another member. On the other hand, if the area of ​​the optical region 10 is too small relative to the area of ​​the substrate 1, it becomes difficult for light to enter the optical region 10, and the desired optical characteristics may not be obtained in the diffused light emitted from the optical element 100. In the optical element 100, by setting the area ratio of the optical region 10 to the area of ​​the substrate 1 to 0.0625 or more, the desired optical characteristics may be obtained in the diffused light emitted from the optical element 100.

[0058] Examples and Comparative Examples Examples and Comparative Examples will be described below, but the present disclosure is not limited to these examples. Examples 1 and 2 shown below are Examples, and Example 3 is a Comparative Example.

[0059] Example 1 In Example 1, the optical element 100 shown in the following Figures 6 to 10 was manufactured, and the optical element 100 was evaluated based on the results of measurements using a confocal microscope. The substrate 1 used had a refractive index of 1.52. In the optical element 100 shown in Figures 6 to 10, of the multiple optical elements 11, each of which is a lens element, the center-to-center distance between adjacent optical elements 11 is, for example, 40.0±1.0 μm. Furthermore, in the optical element 100 shown in Figures 6 to 10, the depth Dp of the optical elements 11 is 10.0±2.0 μm.

[0060] Fig. 6 is a top view photograph showing the optical element 100 according to Example 1. Fig. 7 is a diagram showing a cross-sectional shape of the optical element 100 taken along line VII-VII in Fig. 6. Fig. 8 is an enlarged view of region VIII in Fig. 7. Fig. 9 is a diagram showing the first derivative of Fig. 8. Fig. 10 is a diagram showing the probability density of the diffusion angle in region VIII in Fig. 7.

[0061] FIG. 6 shows a photograph of the optical region 10 of the optical element 100 according to Example 1 taken from above with a confocal microscope. FIG. 7 shows the results of measuring the cross-sectional shape of the optical element 100 taken along line VII-VII in FIG. 6 with a confocal microscope. FIG. 8 shows the cross-sectional shape of region VIII in FIG. 7, i.e., the boundary region 110 in FIG. 6. The first-order differential dZ / dX in FIG. 9 shows the calculation results of the slope a for each position in the cross-sectional shape of the boundary region 110 in FIG. 8. FIG. 10 shows the calculation results of the probability density of the divergence angle γ when light incident on the boundary region 110 shown in FIGS. 7 to 9 is emitted from the optical element 100.

[0062] As shown in FIGS. 7 to 9 , the boundary region 110 shown in FIG. 6 has a smoothly curved, concave, aspherical shape. In the boundary region 110 shown in FIG. 6 , the first derivative dZ / dX gradually changes depending on the position X, as shown in FIG. 9 . That is, the surface inclination a gradually changes in the boundary region 110 shown in FIG. 6 . In the boundary region 110 shown in FIG. 6 , the surface inclination a is not constant, so the refraction angle β of light incident on the boundary region 110 is not constant. The inconsistency in the refraction angle β causes the diffusion angle γ to vary, as shown in FIG. 10 . As a result, the optical element according to Example 1 can reduce localized concentration of light emitted from the optical element 100 and reduce light with locally high luminous intensity.

[0063] Table 4 shows the average value, maximum value, minimum value, and standard deviation of the tilt a and the diffusion angle γ in the optical element 100 according to Example 1.

[0064]

[0065] As shown in Table 4, in the optical element 100 according to Example 1, the average absolute value of the slope a in the boundary region 110 was 0.54, and the variation σ of the slope a was 0.36. Therefore, Example 1 satisfies the above-mentioned condition that "the average absolute value of the slope a in the boundary region 110 is 1.00 or less, and the variation σ of the slope a is 0.10 or more."

[0066] Example 2 In Example 2, the optical element 100 shown in the following Figures 11 to 15 was fabricated, and the optical element 100 was evaluated based on the results of measurements using a confocal microscope. The substrate 1 used had a refractive index of 1.52. In the optical element 100 shown in Figures 11 to 15, of the multiple optical elements 11, each of which is a lens element, the center-to-center distance between adjacent optical elements 11 is, for example, 22.5 ± 2.5 μm. Furthermore, in the optical element 100 shown in Figures 11 to 15, the depth Dp of the optical elements 11 is 5.0 ± 2.0 μm.

[0067] Fig. 11 is a top view photograph showing the optical element 100 according to Example 2. Fig. 12 is a diagram showing the cross-sectional shape of the optical element 100 taken along line XII-XII in Fig. 11. Fig. 13 is an enlarged view of region XIII in Fig. 12. Fig. 14 is a diagram showing the first derivative of Fig. 13. Fig. 15 is a diagram showing the probability density of the diffusion angle in region XIII in Fig. 12.

[0068] The substrate 1 of the optical element 100 according to Example 2 had a refractive index of 1.52. FIG. 11 shows a photograph of the optical region 10 of the optical element 100 according to Example 2 taken from above using a confocal microscope. FIG. 12 shows the results of measuring the cross-sectional shape of the optical element 100 taken along line XII-XII in FIG. 11 using a confocal microscope. FIG. 13 shows the cross-sectional shape of region XIII in FIG. 12, i.e., the boundary region 110 in FIG. 11. The first-order differential dZ / dX in FIG. 14 shows the calculation results of the slope a at each position in the cross-sectional shape of the boundary region 110 in FIG. 13. FIG. 15 shows the calculation results of the probability density of the divergence angle γ when light incident on the boundary region 110 shown in FIGS. 11 to 14 is emitted from the optical element 100.

[0069] As shown in FIGS. 12 to 14 , the boundary region 110 shown in FIG. 11 has a substantially linear inclined surface. However, as shown in FIG. 14 , the first derivative dZ / dX of the boundary region 110 shown in FIG. 11 changes periodically depending on the position X microscopically. Also, as shown in FIG. 11 , the boundary region 110 includes a shape that exhibits periodicity microscopically. In the boundary region 110 shown in FIG. 11 , the inclination a of the surface is not constant microscopically, so the refraction angle β of light incident on the boundary region 110 is not constant. The inconsistency in the refraction angle β results in variations in the diffusion angle γ, as shown in FIG. 15 . As a result, the optical element 100 according to Example 2 can reduce localized concentration of light emitted from the optical element 100 and reduce light with locally high luminous intensity.

[0070] 11 and 14 , in the optical element 100 according to the second example, the boundary region 110 includes a shape in which the surface height Z changes periodically depending on the position X. Because the boundary region 110 includes a shape in which the surface height Z changes periodically depending on the position X, the probability density of the diffusion angle γ approaches a normal distribution, as shown in FIG. 15 . Because the probability density of the diffusion angle γ approaches a normal distribution, in the optical element 100 according to the second example, the shape in which the height Z changes periodically depending on the position X acts as a light diffusion surface. This makes it possible to enhance the diffusion effect of light incident on the boundary region 110 in the optical element 100 according to the second example.

[0071] Table 5 shows the average value, maximum value, minimum value, and standard deviation of the tilt a and the diffusion angle γ in the optical element 100 according to Example 2.

[0072]

[0073] As shown in Table 5, in the optical element 100 according to Example 2, the average absolute value of the slope a in the boundary region 110 was 0.68, and the variation σ of the slope a was 0.62. Therefore, Example 2 satisfies the above-mentioned condition that "the average absolute value of the slope a in the boundary region 110 is 1.00 or less, and the variation σ of the slope a is 0.10 or more."

[0074] Example 3 In Example 3, the optical element 100X was evaluated by ray tracing simulation. Zemax OpticStudio 18.4.1 was used for the ray tracing simulation. The refractive index of the substrate 1X in the optical element 100X was set to 1.52. Other specifications of the optical element 100X were mainly those of the optical element described in Patent Document 1.

[0075] An optical element 100X according to a third example will be described with reference to FIGS. 16 to 20. FIG. 16 is a perspective view showing the behavior of light Li incident on a boundary region 110X of an optical element 100X according to Example 3. FIG. 17 is a side view showing the behavior of light Li incident on a boundary region 110X of an optical element 100X according to Example 3. FIG. 18 is a diagram showing light Lt irradiated onto an irradiation surface S when light Li is incident on the boundary region 110X of an optical element 100X according to Example 3 at a first-surface incident angle α of 10 degrees. FIG. 19 is a diagram showing light Lt irradiated onto an irradiation surface S when light Li is incident on the boundary region 110X of an optical element 100X according to Example 3 at a first-surface incident angle α of 20 degrees. FIG. 20 is a diagram showing light Lt irradiated onto an irradiation surface S when light Li is incident on the boundary region 110X of an optical element 100X according to Example 3 at a first-surface incident angle α of 30 degrees.

[0076] As shown in FIG. 17 , an optical element 100X according to the third example has a substrate 1X including a first surface 1aX and a second surface 1bX located opposite the first surface 1aX. The substrate 1X includes an optical region 10X in which optical elements 11X are arranged in a portion of the first surface 1aX. The substrate 1X also includes a peripheral region 12X, which is provided around the optical region 10X on the surface of the substrate 1X where the optical region 10X is provided, and in which no optical elements 11X are arranged. The optical elements 11X included in the optical region 10X are lens elements. The optical region 10X includes a boundary region 110X defined similarly to the boundary region 110 described above. In the optical element 100X, the boundary region 110X is a plane substantially perpendicular to the second surface 1bX. In that the boundary region 110X is a plane substantially perpendicular to the second surface 1bX, the boundary region 110X in the optical element 100X is a plane with an infinite slope a.

[0077] As shown in FIG. 17, light Li incident on the boundary region 110X at the first surface incident angle α is refracted at the boundary region 110X and transmitted through the interior of the substrate 1X of the optical element 100X, with much of it being totally reflected at the second surface 1bX. The return light Lr reflected at the second surface 1bX is returned to the side of the optical element 100X from which the light Li entered. In an optical element 100X including a boundary region 110X that is a plane with an infinite slope a, the light Li incident on the boundary region 110X is likely to be totally reflected at the second surface 1bX. As a result, the return light Lr increases, and as shown in FIGS. 18 to 20, less light Lt reaches the irradiation surface S. The light extraction efficiency from the optical element 100X is 67.2% in the example shown in FIG. 18, 44.7% in the example shown in FIG. 19, and 0.19% in the example shown in FIG. 20. The light Lt shown in FIGS. 18 and 19 is light with a locally high luminous intensity that is generated by the local concentration of light incident on the boundary region between the optical region and the peripheral region.

[0078] As described above, in the optical element 100X, the amount of returned light due to total reflection increases, and the light extraction efficiency of the diffused light emitted from the optical element 100X decreases. In the optical element 100X, the light incident on the boundary region between the optical region and the peripheral region is locally concentrated, and light with locally high luminous intensity is emitted from the optical element.

[0079] (Evaluation Results of the Optical Element 100 According to Example 1 by Simulation) The optical element 100 according to Example 1 was evaluated by ray tracing simulation. Zemax OpticStudio 18.4.1 was used for the ray tracing simulation.

[0080] 21 to 25, the evaluation results of the optical element 100 according to Example 1 by simulation will be described. FIG. 21 is a perspective view showing the behavior of light Li incident on the boundary region 110 of the optical element 100 according to Example 1. FIG. 22 is a side view showing the behavior of light Li incident on the boundary region 110 of the optical element 100 according to Example 1. FIG. 23 is a diagram showing diffused light Ls irradiated onto the irradiation surface S when light Li is incident on the boundary region 110 of the optical element 100 according to Example 1 at a first-surface incident angle α of 10 degrees. FIG. 24 is a diagram showing diffused light Ls irradiated onto the irradiation surface S when light Li is incident on the boundary region 110 of the optical element 100 according to Example 1 at a first-surface incident angle α of 20 degrees. FIG. 25 is a diagram showing diffused light Ls irradiated onto the irradiation surface S when light Li is incident on the boundary region 110 of the optical element 100 according to Example 1 at a first-surface incident angle α of 30 degrees.

[0081] As shown in FIG. 22, light Li incident on the boundary region 110 at the first surface incident angle α is refracted at the boundary region 110, passes through the interior of the substrate 1 of the optical element 100, and then is emitted through the second surface 1b without being totally reflected at the second surface 1b. By reducing total reflection at the second surface 1b, the amount of returned light is reduced, and as shown in FIGS. 23 to 25, the amount of diffused light Ls reaching the irradiation surface S increases. The light extraction efficiency from the optical element 100 is 96.1% in the example shown in FIG. 23, 96.3% in the example shown in FIG. 24, and 96.6% in the example shown in FIG. 20. Furthermore, the diffused light Ls shown in FIGS. 23 to 25 is emitted from the optical element 100 and then spreads out to irradiate the irradiation surface S. The diffused light Ls does not include light with locally high luminous intensity.

[0082] As described above, the optical element 100 according to Example 1 can increase the light extraction efficiency of diffused light emitted from the optical element 100 and reduce light with locally high luminous intensity. Although the examples shown in Figures 21 to 25 show the optical element 100 according to Example 1, similar results can be obtained with the optical element 100 according to Example 2.

[0083] Second Embodiment A light source device 200 according to a second embodiment will be described. Note that the same names and symbols as those in the already described embodiments indicate the same or similar members or configurations, and detailed descriptions thereof will be omitted as appropriate.

[0084] Fig. 26 is a schematic perspective view showing an example of a light source device 200 according to the second embodiment. As shown in Fig. 26, the light source device 200 has a light source 150 and an optical element 100 arranged on the emission side of the light source 150. The optical element 100 diffuses light L0 from the light source 150. The light source device 200 emits diffused light Ls by the optical element 100. In the example shown in Fig. 26, the light source device 200 emits diffused light Ls whose outer edge has a substantially rectangular shape with a longitudinal direction when viewed in the +Z direction.

[0085] In this embodiment, the light source device 200 includes the optical element 100, which increases the light extraction efficiency of the diffused light Ls emitted from the light source device 200 and reduces light with locally high luminous intensity.

[0086] In the light source device 200 shown in FIG. 26 , the optical element 100 is disposed with the first surface 1a, on which the optical region 10 is disposed, facing the light source 150. The light source device 200 is used for sensing or lighting applications. In sensing applications, for example, in LiDAR (Light Detection and Ranging), the light source device 200 can be used as a light projecting device that projects diffused light for measurement into a measurement range. In lighting applications, for example, in a projection device such as a projector, the light source device 200 can be used as an illumination device that illuminates a spatial modulator such as a liquid crystal panel with diffused light. The light source device 200 can increase the light extraction efficiency of the diffused light Ls emitted from the light source device 200 and reduce light with locally high luminous intensity. Therefore, using the light source device 200 for sensing applications can improve the accuracy of sensing devices such as LiDAR. Furthermore, by using the light source device 200 for lighting purposes, the quality of the image projected by a projection device such as a projector can be improved.

[0087] A semiconductor laser can be used as the light source 150. However, the light source 150 is not limited to a semiconductor laser, and a laser light source other than a semiconductor laser, such as a solid-state laser, or a light source other than a laser light source, such as a light-emitting diode, can also be used. The emission peak wavelength of the light emitted from the light source 150 can be selected appropriately depending on the application of the light source device 200.

[0088] The outer edge shape of the diffused light Ls when viewed in the +Z direction follows the outer edge shape of the optical elements 11 arranged in the optical region 10 of the optical element 100 when viewed in the +Z direction. The light source device 200 can emit diffused light Ls with various outer edge shapes depending on the outer edge shape of the optical elements 11 when viewed in the +Z direction. FIG. 27 is a diagram showing a first example of diffused light Ls emitted from the light source device 200. FIG. 28 is a diagram showing a second example of diffused light Ls emitted from the light source device 200. FIG. 29 is a diagram showing a third example of diffused light Ls emitted from the light source device 200.

[0089] The first example shown in Fig. 27 shows diffused light Ls whose outer edge shape when viewed in the +Z direction is approximately square. The second example shown in Fig. 28 shows diffused light Ls whose outer edge shape when viewed in the +Z direction is approximately rectangular with the X direction as the longitudinal axis. The third example shown in Fig. 29 shows diffused light Ls whose outer edge shape when viewed in the +Z direction is approximately regular hexagonal. In addition to these, the light source device 200 can emit diffused light Ls whose outer edge shape is approximately circular, approximately elliptical, approximately polygonal, etc., depending on the outer edge shape of the optical element 11 when viewed in the +Z direction.

[0090] 30 and 31 are diagrams showing the intensity profile of diffused light Ls emitted from the light source device 200. The intensity profile of diffused light Ls refers to a collection of intensity values ​​obtained from points equally spaced along a line segment path that is approximately perpendicular to the direction of travel of the diffused light Ls. In FIGS. 30 and 31, the horizontal axis represents angle, and the vertical axis represents intensity. FIG. 30 shows the intensity profile of flat-top diffused light Ls. FIG. 31 shows the intensity profile of 1 / cosθ diffused light Ls. The intensity profile of diffused light Ls can be determined appropriately depending on the shape or arrangement of the optical element 11, etc.

[0091] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0092] All ordinal numbers, quantitative numbers, and other figures used in the description of the embodiments are provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated figures. Furthermore, the connection relationships between components are provided as examples to specifically explain the technology of the present disclosure, and do not limit the connection relationships that realize the functions of the present disclosure.

[0093] The optical element and light source device according to the present disclosure can increase the light extraction efficiency of diffused light emitted from the optical element and reduce light with locally high luminous intensity, and can therefore be used in projection devices such as projectors, sensing devices such as LiDAR, etc. However, the optical element and light source device according to the embodiment are not limited to these, and can be applied to a variety of fields that use optical techniques.

[0094] This application claims priority based on Japanese Patent Application No. 2024-17281, filed February 7, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0095] 1 Substrate 1a First surface 1b Second surface 10 Optical region 11, 11-1 to 11-4 Optical elements 11C-1, 11C-2 Optical axis 11T-1, 11T-2 Vertex 110 Boundary region 12 Peripheral region 12E End 13a First anti-reflection film 13b Second anti-reflection film 100 Optical element 150 Light source 200 Light source device a Inclination a' Inclination angle b Width of substrate in X direction c Width of substrate in Y direction d Radius Dp Depth Ds Distance Li Incident light Lr Return light Ls Diffused light Lt Light Po1, Po2 Position S Irradiated surface α First surface incident angle β Refraction angle ε Second surface incident angle θ Normal angle

Claims

1. An optical element having a substrate including a first surface and a second surface located opposite the first surface, wherein the substrate includes: an optical region in which at least one optical element is arranged in a portion of at least one of the first and second surfaces; and a peripheral region on the surface of the substrate where the optical region is arranged, the peripheral region being arranged around the optical region and in which no optical element is arranged, wherein the optical element is a lens element, and wherein, in a cross section including the optical axis of at least one of the optical elements closest to the peripheral region, the cross-sectional region extending from the vertex of the optical element through which the optical axis passes to the end of the peripheral region closest to the optical element is defined as a boundary region, the average absolute value of the slope of the surface in the boundary region being 1.00 or less and the variation σ being 0.10 or more.

2. The optical element according to claim 1, wherein in the substrate, the optical region is recessed relative to the peripheral region.

3. The optical element according to claim 1 or 2, wherein the optical region includes a plurality of the optical elements, and the plurality of optical elements are arranged two-dimensionally without exposing any flat surface.

4. The optical element according to claim 1 or 2, wherein the ratio of the area of the optical region to the area of the substrate is 0.0625 or more and 0.9025 or less.

5. The optical element according to claim 3, wherein the distance between the vertices of adjacent optical elements among the plurality of optical elements is 10 μm or more and 200 μm or less.

6. An optical element according to claim 1 or 2, wherein the depth between the vertex of the optical element and the edge of the peripheral region in the direction along the optical axis is 3 μm or more and 100 μm or less.

7. An optical element according to claim 1 or 2, wherein the FWHM is 20 degrees or more when parallel light having an emission peak wavelength of 300 nm or more and 1000 nm or less is incident thereon.

8. An optical element according to claim 1 or 2, wherein when parallel light having an emission peak wavelength of 300 nm or more and 1000 nm or less is incident, the total light transmittance of the diffused light emitted from the optical element is 93% or more.

9. A light source device comprising: a light source; and an optical element according to claim 1 or 2, which is arranged on the light emission side of the light source; wherein the optical element diffuses light from the light source; and the optical element emits diffused light.

10. A light source device according to claim 9, wherein the optical element is arranged with the surface on which the optical region is arranged facing the light source side, and is used for sensing or lighting purposes.

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