Microlens array and light source apparatus

Abstract

Provided is a microlens array that is, even when light having a small diameter enters, capable of achieving wide-angle and uniform diffusion by suppressing a change in a diffusion profile. A microlens array (10) comprises: a base material (11) having a first surface (12); and a plurality of aspherical lenses (13) disposed on the first surface (12). The aspherical lenses (13) are arranged in a one-dimensional direction. In at least one row of the aspherical lenses (13), the average pitch of the aspherical lenses (13) is 30 μm or less, and the average inclination is 0.300 or more.

Description

Micro lens array and light source device

[0001] The present disclosure relates to a micro lens array and a light source device.

[0002] A micro lens array is known as an optical element that diffuses incident light and emits diffused light. Also, a light source device having the micro lens array is known.

[0003] From the viewpoint of use in illumination and sensing, the micro lens array is required to have the characteristic of being able to irradiate diffused light widely and uniformly. For example, Patent Document 1 discloses a micro lens array that can equalize the light amount of an emitted light beam even when the irradiation range is wide.

[0004] Japanese Patent No. 6424418

[0005] However, in the micro lens array described in Patent Document 1, when the diameter of the incident light becomes small, the diffusion profile of the micro lens array changes, and it may be difficult to realize uniform diffusion while maintaining wide-angle diffusibility. From the viewpoint of device miniaturization, it is desirable to suppress changes in the diffusion profile and maintain wide-angle and uniform diffusion even when light of a small diameter is incident.

[0006] An aspect of the present disclosure aims to provide a micro lens array that can suppress changes in the diffusion profile and achieve wide-angle and uniform diffusion even when light of a small diameter is incident.

[0007] The micro lens array according to an aspect of the present disclosure includes a base material having a first surface, and a plurality of aspherical lenses disposed on the first surface. The aspherical lenses are arranged in a one-dimensional direction, and in at least one row of the aspherical lenses, the average pitch of the aspherical lenses is 30 μm or less, and the average inclination is 0.300 or more.

[0008] According to an aspect of the present disclosure, wide-angle and uniform diffusion can be realized even when light of a small diameter is incident.

[0009] This is a schematic cross-sectional view of a microlens array according to one embodiment. This is a top view image of a microlens array according to one embodiment. This is the diffusion profile of a microlens array with an average pitch of 20 μm in the X direction. This is the diffusion profile of a microlens array with an average pitch of 70 μm in the X direction. This is the difference in relative intensity between the diffusion profile of a 3 mm optical diameter and the diffusion profile of a 0.3 mm optical diameter of a microlens array with an average pitch of 20 μm in the X direction. This is the difference in relative intensity between the diffusion profile of a 3 mm optical diameter and the diffusion profile of a 0.3 mm optical diameter of a microlens array with an average pitch of 70 μm in the X direction. This is the relationship between the average pitch of the microlens array according to one embodiment and the maximum value of the difference in relative intensity between the diffusion profile of a 3 mm optical diameter and the diffusion profile of a 0.3 mm optical diameter. This is the relationship between the FOV and the average slope of the microlens array according to one embodiment. This is a schematic diagram of a light source device to which the microlens array according to one embodiment is applied. This is the diffusion profile in the X direction of the embodiment. These are the relative intensity differences between the diffusion profile with a light diameter of 3 mm and the diffusion profile with a light diameter of 0.2 mm in the example, and the relative intensity differences between the diffusion profile with a light diameter of 3 mm and the diffusion profile with a light diameter of 0.4 mm.

[0010] The embodiments for carrying out the invention will be described in detail below with reference to the drawings. However, the embodiments shown below are illustrative examples of microlens arrays for realizing the technical concept of one embodiment of the present invention, and are not limited to those described below. Note that the size, positional relationships, etc. of the components shown in each drawing may be exaggerated for clarity of explanation. In each drawing, the same reference numerals are used for the same components, and redundant explanations are omitted as appropriate.

[0011] In the drawings shown below, a Cartesian coordinate system comprising the X, Y, and Z axes may be used to represent directions. The X direction along the X axis indicates a predetermined direction on the first surface of the microlens array according to the embodiment. The Y direction along the Y axis indicates a direction perpendicular to the X direction on the same surface of the first surface. The Z direction along the Z axis indicates a direction perpendicular to the first surface.

[0012] In the X direction, the direction of the arrow is denoted as the +X direction, and the opposite direction of the +X direction is denoted as the -X direction. In the Y direction, the direction of the arrow is denoted as the +Y direction, and the opposite direction of the +Y direction is denoted as the -Y direction. In the Z direction, the direction of the arrow is denoted as the +Z direction, and the opposite direction of the +Z direction is denoted as the -Z direction. In this embodiment, light traveling in the +Z direction is assumed to be incident on the microlens array and emitted from the microlens array. In this specification, a top view means viewing the microlens array according to the embodiment from the +Z direction side. However, these directional expressions do not limit the directions of one embodiment of the present invention.

[0013] In this specification, "small diameter of incident light" means that the diameter of the incident light is 1 mm or less.

[0014] In this specification, "wide-angle diffusion," or "wide-angle diffusion," means that the FOV (Field of View) is 40° or greater. "FOV" refers to the field of view, and in this specification, it means the angular width at which the relative intensity of the desired one-dimensional diffusion profile is 0.5 or greater. "Relative intensity" refers to the intensity of the desired one-dimensional diffusion profile normalized with the average intensity of the diffused light in the diffusion angle range of -10° to +10° set to 1.

[0015] In this specification, "uniform diffusion" means that the relative intensity of the diffusion profile is in the range of 0.85 to 1.15 in the range of the largest angular width between any two diffusion angles where the relative intensity of the diffusion profile is 0.85.

[0016] In this specification, "aspherical" means that the absolute value of the conic coefficient of the lens is 0.05 or greater.

[0017] <Configuration of a Microlens Array According to One Embodiment> The overall configuration of a microlens array 10 according to one embodiment will be described with reference to Figures 1A and 1B. Figure 1A is a schematic cross-sectional view of the microlens array 10, and Figure 1B is a top view image.

[0018] The microlens array 10 comprises a substrate 11 having a first surface 12, and a plurality of aspherical lenses 13 arranged on the first surface 12. For example, the plurality of aspherical lenses 13 form rows in the X direction, and these rows are aligned in the Y direction. As a result, the plurality of aspherical lenses 13 are arranged in a square grid, as shown in Figure 1B. Figure 1A schematically shows a cross-section of one row of aspherical lenses 13 in the X direction. The aspherical lenses 13 are arranged in a one-dimensional direction on the first surface 12, and in at least one row of aspherical lenses 13, the average pitch of the aspherical lenses 13 is 30 μm or less, and the average inclination is 0.300 or more.

[0019] In this specification, average pitch means the average value of the distance between the vertices 14 of adjacent aspherical lenses 13 arranged in a target range. Specifically, for example, the average pitch of one array of aspherical lenses arranged in the X direction corresponds to the average value of the X-direction component of the distance between the vertices 14 of adjacent aspherical lenses 13. Furthermore, the average pitch of a range in which two or more rows of aspherical lenses are arranged corresponds to the average value of the X-direction component of the distance between the vertices 14 of adjacent aspherical lenses 13 in the X direction and the Y-direction component of the distance between the vertices 14 of adjacent aspherical lenses 13 in the Y direction.

[0020] The average slope refers to the average value of the first derivatives of each shape of the aspherical lenses 13 arranged within the target range. In this case, the first derivatives are obtained at intervals of 0.5 μm, and the average value is obtained.

[0021] The average pitch and average inclination can be measured based on the cross-sectional profile of each aspherical lens 13 obtained from the measurement results, which are obtained by measuring the three-dimensional shape of the aspherical lens 13 within the target range. Here, the cross-sectional profile of each aspherical lens 13 is obtained in a cross-section that passes through the vertex 14 of the aspherical lens 13 along the arrangement direction of the aspherical lens 13 and is perpendicular to the first surface 12 of the substrate 11. The three-dimensional shape of the aspherical lens 13 can be measured using a laser microscope (for example, a VK-X3000 manufactured by Keyence Corporation).

[0022] A microlens array 10 according to one embodiment, having the above configuration, can achieve wide-angle and uniform diffusion even when light of a small diameter is incident on it.

[0023] Below, we will explain in detail (1) the average pitch in the arrangement of the aspherical lenses 13 and (2) the average inclination in the arrangement of the aspherical lenses 13.

[0024] <Average pitch in the arrangement of aspherical lenses> We will examine the effect of the average pitch of multiple aspherical lenses 13 arranged on the first surface 12 of the substrate 11 on the diffusion profile when the incident light diameter to the microlens array 10 is changed. As will be described later, by making the average pitch of the aspherical lenses 13 30 μm or less in at least one row of aspherical lenses 13 arranged in the one-dimensional direction on the first surface 12, it is possible to impart uniform diffusion to the microlens array 10 while suppressing changes in the diffusion profile when the incident light diameter decreases. Suppressing changes in the diffusion profile when the incident light diameter decreases ultimately contributes to achieving wide-angle and uniform diffusion when the incident light diameter decreases.

[0025] Figure 2 shows the simulation results of the diffusion profile in the X direction when light with diameters of 3 mm and 0.3 mm is incident on a microlens array 10 in which 62,500 aspherical lenses 13 are arranged at an average pitch of 20 μm in both the X and Y directions (250 rows in the X direction and 250 rows in the Y direction). The incident light wavelength was set to 660 nm, and the aspherical lenses 13 were concave lenses.

[0026] As shown in Figure 2, if the average pitch is 20 μm, regardless of whether the incident light has a diameter of 3 mm or 0.3 mm, the relative intensity falls within the range of 0.85 to 1.15 in the widest of the two angular widths of diffusion angles where the relative intensity is 0.85. This shows that uniform diffusion can be obtained even when light of a small diameter is incident.

[0027] Figure 3 shows the simulation results of the diffusion profile in the X direction when light with optical diameters of 3 mm and 0.3 mm is incident on a microlens array 10, which in the example of Figure 2 had an average pitch of 70 μm in the X and Y directions, and all other conditions were the same.

[0028] As shown in Figure 3, when the average pitch is 70 μm, uniform diffusion is obtained for incident light with a diameter of 3 mm. However, when light with a diameter of 0.3 mm is incident, the relative intensity exceeds 1.15 at a diffusion angle of ±19°. In other words, when the average pitch is 70 μm, the diffusion profile changes when light of a small diameter is incident, making it difficult to obtain uniform diffusion.

[0029] Further investigation will be conducted into the effect of average pitch on the diffusion profile when light of a small diameter is incident. Figure 4 shows the difference in relative intensity between the diffusion profile for a light diameter of 3 mm and the diffusion profile for a light diameter of 0.3 mm in Figure 2, for each diffusion angle. In this case, if the maximum absolute value of the difference in relative intensity is 0.15 or less, it was evaluated that the change in the diffusion profile when the diameter of the incident light decreases was suppressed.

[0030] As shown in Figure 4, if the average pitch is 20 μm, the difference in relative intensity across the entire diffusion profile is within the range of ±0.15, indicating that there is no significant change in the diffusion profile depending on the diameter of the incident light.

[0031] Figure 5 shows the difference in relative intensity between the diffusion profile with a light diameter of 3 mm and the diffusion profile with a light diameter of 0.3 mm in Figure 3, for each diffusion angle.

[0032] As shown in Figure 5, when the average pitch is 70 μm, there are intervals where the difference in relative intensity is -0.15 or less, that is, intervals where the absolute value of the difference in relative intensity exceeds 0.15, indicating that the diffusion profile cannot be maintained when the diameter of the incident light decreases.

[0033] The comparison of Figures 4 and 5 suggests that reducing the average pitch in the array of aspherical lenses 13 can suppress changes in the diffusion profile when the incident light diameter decreases in the microlens array 10. This is presumed to be due to the following mechanism.

[0034] The diffusion characteristics of the microlens array 10 are formed by the overlapping of light diffused by the aspherical lenses 13. When the average pitch is large, as the diameter of the incident light decreases, the number of lenses contributing to the diffusion characteristics decreases, and variations in the shape of individual lenses have a significant impact on the diffusion characteristics, leading to changes in the diffusion profile. On the other hand, when the average pitch is small, a sufficient number of lenses contribute to the diffusion characteristics, so the influence of variations in the shape of individual lenses is suppressed, and changes in the diffusion profile can be suppressed.

[0035] Furthermore, to examine the details, simulations were conducted to investigate the changes in the diffusion profile when the average pitch in the X and Y directions was set to values ​​different from those in the examples shown in Figures 4 and 5. Figure 6 plots the maximum absolute value of the relative intensity difference between the diffusion profile with a light diameter of 3 mm and the diffusion profile in the X direction with a light diameter of 0.3 mm against the average pitch in the X and Y directions.

[0036] As shown in Figure 6, if the average pitch is 30 μm or less, the difference in relative intensity is 0.15 or less across the entire diffusion profile, indicating that no significant change in the diffusion profile occurs depending on the diameter of the incident light. From this, it can be considered that by setting the average pitch of the aspherical lenses 13 to 30 μm or less in at least one row of aspherical lenses 13 arranged in the one-dimensional direction on the first surface 12, changes in the diffusion profile when the diameter of the incident light decreases can be suppressed.

[0037] From the viewpoint of suppressing changes in the diffusion profile when the diameter of the incident light becomes smaller, it is preferable that in at least one row of aspherical lenses 13 arranged in a one-dimensional direction on the first surface 12, the average pitch of the aspherical lenses 13 is 25 μm or less.

[0038] The arrangement direction of the aspherical lenses 13 is not particularly limited, but from the viewpoint of obtaining a square diffusion pattern, it is preferable that they be arranged in two perpendicular directions, such as the X and Y directions. On the other hand, if a circular diffusion pattern or the like is to be obtained, it is preferable that the arrangement direction of the aspherical lenses is not perpendicular, i.e., staggered.

[0039] Furthermore, when the aspherical lenses 13 are arranged in the X and Y directions, the average pitches of the aspherical lenses 13 in the X and Y directions do not necessarily have to be the same. From the viewpoint of obtaining diffusion patterns such as squares or perfect circles, it is preferable that the average pitches in the X and Y directions are equal, while from the viewpoint of obtaining diffusion patterns such as rectangles or ellipses, it is preferable that the average pitches in the X and Y directions are different.

[0040] From the viewpoint of further suppressing changes in the diffusion profile when the diameter of the incident light becomes smaller and diffusing light in two dimensions, the average pitch measured for all aspherical lenses 13 arranged on the first surface 12 is preferably 30 μm or less, more preferably 25 μm or less, and even more preferably 20 μm or less.

[0041] From the viewpoint of suppressing the generation of diffraction spots, in at least one row of aspherical lenses 13 arranged in a one-dimensional direction on the first surface 12, the average pitch of the aspherical lenses 13 is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more.

[0042] From the viewpoint of diffusing light in two dimensions while suppressing the generation of diffraction spots, the average pitch measured for all aspherical lenses 13 arranged on the first surface 12 is preferably 5 μm or more, more preferably 7 μm or more, and even more preferably 9 μm or more on the first surface 12.

[0043] <Average inclination in the array of aspherical lenses> Next, we will examine the influence of the average inclination of the plurality of aspherical lenses 13 arranged on the first surface 12 of the substrate 11 on the diffusion angle of the microlens array 10. As will be described later, on the first surface 12, in at least one row of the aspherical lenses 13 arranged in the one-dimensional direction, by setting the average inclination of the aspherical lenses 13 to 0.300 or more, wide-angle diffusibility can be imparted to the microlens array 10.

[0044] Regarding the influence of the average inclination in the array of aspherical lenses on the diffusion angle, we examined it based on the simulation of the diffusion profile of the microlens array 10 in which the aspherical lenses 13 were arranged under the conditions shown in Table 1. In each example, the number of aspherical lenses 13 was 250 rows in the X direction, 250 rows in the Y direction, for a total of 62,500 lenses, the conic coefficient (k) was -1, the incident light diameter was 0.3 mm, the wavelength of the incident light was 660 nm, and the aspherical lenses 13 were concave lenses, all unified. Table 1 shows the average inclination in the X direction and the FOV in the X direction for each example.

[0045]

[0046] Fig. 7 plots the relationship between the average inclination and the FOV for each example in Table 1. According to Fig. 7, it can be read that as the average inclination increases, the FOV also tends to increase. Specifically, it can be seen that by setting the average inclination to 0.300 or more, a wide-angle diffusion with an FOV of 40° or more can be realized.

[0047] From this, it can be seen that on the first surface 12, in at least one row of the aspherical lenses 13 arranged in the one-dimensional direction, by setting the average inclination of the aspherical lenses 13 to 0.300 or more, wide-angle diffusibility can be imparted to the microlens array 10.

[0048] From the perspective of obtaining wide-angle diffusibility, on the first surface 12, in at least one row of the aspherical lenses 13 arranged in the one-dimensional direction, the average inclination of the aspherical lenses 13 is preferably 0.330 or more, and more preferably 0.350 or more.

[0049] From the viewpoint of obtaining even wider-angle diffusion, the average inclination of the aspherical lens 13 is preferably 0.300 or more, more preferably 0.330 or more, and even more preferably 0.350 or more on the first surface 12.

[0050] Furthermore, in the first surface 12, in at least one row of aspherical lenses 13 arranged in a one-dimensional direction, the upper limit of the average inclination of the aspherical lenses 13 is not particularly limited, but from the viewpoint of suppressing light loss due to total internal reflection, it is preferably 6.500 or less, and more preferably 5.000 or less.

[0051] As described above, by setting the average pitch and average tilt of the microlens array 10 according to one embodiment within the above range, even when light of a small diameter is incident, changes in the diffusion profile can be suppressed and wide-angle and uniform diffusion can be achieved. Hereinafter, preferred embodiments of the microlens array 10 according to one embodiment will be described from viewpoints other than average pitch and average tilt.

[0052] In the microlens array 10, in at least one row of aspherical lenses 13 arranged in one dimension on the first surface 12, the pitch variation is preferably 0.20 or less, and more preferably 0.15 or less, from the viewpoint of obtaining good cutoff, i.e., a steep rise in the diffusion profile. On the other hand, from the viewpoint of suppressing speckle noise, i.e., local concentration of diffuse light caused by diffracted light, the pitch variation is preferably 0.03 or more, and more preferably 0.05 or more. In this specification, pitch variation means the value obtained by dividing the standard deviation of the pitch of the aspherical lenses 13 in the target range by the average value of the pitch.

[0053] Furthermore, from the viewpoint of obtaining good cutoff performance, the pitch variation of the microlens array 10, when measured for all aspherical lenses 13 arranged on the first surface 12, is preferably 0.20 or less, and more preferably 0.15 or less. On the other hand, from the viewpoint of suppressing speckle noise, i.e., local concentration of diffused light caused by diffracted light, it is preferably 0.03 or more, and more preferably 0.05 or more.

[0054] In the microlens array 10, in at least one row of aspherical lenses 13 arranged in a one-dimensional direction on the first surface 12, the variation in the radius of curvature of the aspherical lenses 13 is preferably 0.25 or less, and more preferably 0.20 or less, from the viewpoint of obtaining good cutoff performance. On the other hand, from the viewpoint of suppressing speckle noise, it is preferably 0.05 or more, and more preferably 0.10 or more. In this specification, the variation in radius of curvature means the value obtained by dividing the standard deviation of the radius of curvature of the aspherical lenses 13 in the target range by the average value of the radius of curvature.

[0055] From the viewpoint of obtaining good cutoff performance, the variation in the radius of curvature of the microlens array 10, when measured for all aspherical lenses 13 arranged on the first surface 12, is preferably 0.25 or less, and more preferably 0.20 or less. On the other hand, from the viewpoint of suppressing speckle noise, it is preferably 0.05 or more, and more preferably 0.10 or more.

[0056] In the microlens array 10, in at least one row of aspherical lenses 13 arranged in a one-dimensional direction on the first surface 12, the depth variation of the aspherical lenses 13 is preferably 0.50 μm or more, and more preferably 0.80 μm or more, from the viewpoint of suppressing speckle noise. On the other hand, from the viewpoint of obtaining better diffusion characteristics, it is preferably 4 μm or less, and more preferably 2.5 μm or less. In this specification, depth variation means the standard deviation of the depth of the aspherical lenses 13 in the range to be considered.

[0057] When measuring the depth variation of the microlens array 10 with respect to all aspherical lenses 13 arranged on the first surface 12, it is preferably 0.50 μm or more, and more preferably 0.80 μm or more. On the other hand, from the viewpoint of obtaining better diffusion characteristics, it is preferably 4 μm or less, and more preferably 2.5 μm or less.

[0058] Pitch variation, radius of curvature variation, and depth variation can be measured within the target range by measuring the three-dimensional shape of the aspherical lens 13 and based on the profile of the cross-sectional shape of each aspherical lens 13 obtained from the measurement results. Here, the profile of the cross-sectional shape of each aspherical lens 13 is obtained in a cross section that passes through the vertex 14 of the aspherical lens 13 and is perpendicular to the first surface 12 of the base material 11. The radius of curvature of the aspherical lens 13 can be obtained by fitting the profile of the cross-sectional shape of the aspherical lens 13 with the following formula (1).

[0059]

[0060] In equation (1), Z represents the depth of the aspherical lens, r is the distance in the one-dimensional direction from which the cross-sectional profile was obtained, R is the radius of curvature of the aspherical lens, and k is the conic coefficient of the aspherical lens. Fitting refers to identifying the combination of R and k that minimizes the sum of the squares of the difference between the depth Z value obtained by equation (1) for each distance of the aspherical lens and the depth value obtained from the measured cross-sectional profile for each distance of the aspherical lens. As a result of fitting, the obtained R is taken as the radius of curvature of the aspherical lens 13.

[0061] As described above, variations may be introduced in the pitch, radius of curvature, and lens depth of the aspherical lens 13 in the microlens array 10. On the other hand, in the microlens array 10 according to one embodiment, if the average pitch and average inclination are within the preferred range described above, wide-angle and uniform diffusion can be achieved even when light of a small diameter is incident, even if the variations in the pitch and radius of curvature of the aspherical lens are not within the preferred range.

[0062] From the viewpoint of broadly diffusing incident light over a short distance and miniaturizing the device, the microlens array 10 preferably has an FOV of 40° or more, and more preferably 50° or more, when incident light with a wavelength of 660 nm.

[0063] From the viewpoint of improving light utilization efficiency, the microlens array 10 preferably has a total light transmittance of 88% or more, and more preferably 90% or more, when light with a wavelength of 660 nm is incident on it.

[0064] The aspherical lens 13 may be a concave lens or a convex lens, but from the viewpoint of productivity, it is preferable that it be a concave lens. Furthermore, from the viewpoint of suppressing stray light, it is preferable that it be either a concave lens only or a convex lens only.

[0065] The base material 11 can be composed of glass material or resin material, etc. The material used for the base material 11 can be appropriately selected depending on the application of the microlens array 10, but from the viewpoint of heat resistance and light resistance, glass material is preferred.

[0066] From the viewpoint of obtaining wide-angle diffusion, the refractive index of the substrate 11 with respect to light at a wavelength of 590 nm is preferably 1.450 or higher, and more preferably 1.500 or higher.

[0067] The wavelength used, that is, the incident light to the microlens array 10, is preferably transparent to the substrate 11, and is preferably in the wavelength range of 300 to 1000 nm. Here, "transparent" means that when light of the desired wavelength is incident at an incident angle of 0 degrees, the transmittance is 80% or more.

[0068] <Examples of Microlens Array Applications> Figure 8 is a schematic diagram of a light source device 20 to which a microlens array 10 according to one embodiment is applied. In the light source device 20, the microlens array 10 is arranged with the first surface 12 on which the aspherical lens 13 is arranged facing the light source 21. The light source device 20 is used for sensing or illumination applications. For sensing applications, for example, in LiDAR (Light Detection and Ranging), the light source device 20 can be used as a light source device that projects diffuse light for measurement into the measurement range. For illumination applications, for example, in projection devices such as projectors, the light source device 20 can be used as an illumination device that illuminates a spatial modulator such as a liquid crystal panel with diffuse light. The light source device 20 can realize uniform and wide-angle diffuse light Ls even when the light diameter of the light source 21 is small. Therefore, by using the light source device 20 in sensing or illumination applications, it is possible to contribute to the miniaturization of devices.

[0069] <Method for Manufacturing a Microlens Array> One embodiment of the method for manufacturing a microlens array 10 will be described. The method for manufacturing the aspherical lenses 13 in the microlens array 10 is not particularly limited, but for example, they are formed by wet etching a pre-treated substrate. The pre-treatment is preferably a method in which pulsed laser light is irradiated at a certain position on the substrate 11 to modify a part of the interior of the substrate and to give a density distribution in the thickness direction at the position irradiated with pulsed laser light.

[0070] The shape of the aspherical lens 13 is determined by a combination of factors, including the wavelength, frequency, power, pulse width, and focal position of the laser light used during pretreatment. Preferred conditions for a manufacturing method according to one embodiment are described below.

[0071] In the manufacturing method according to one embodiment, the wavelength of the laser light is not particularly limited, but examples include 1026 nm, 1064 nm, and 532 nm, with 1064 nm being preferred. The frequency of the laser light is preferably 10 to 50 kHz.

[0072] From the viewpoint of providing sufficient modification to the substrate to form a lens, the laser light power is preferably 0.60 W or more. On the other hand, from the viewpoint of obtaining a flat diffusion profile, it is preferably 1.00 W or less, and more preferably 0.90 W or less.

[0073] The pulse width of the laser light is preferably 20 ps or less, and more preferably 15 ps or less, because rapid cooling is required after irradiation. The lower limit of the pulse width is not particularly limited, but it may be, for example, 1 ps or more.

[0074] The focal position of the laser beam is preferably -0.250 to +0.100 mm, and more preferably -0.150 to +0.00 mm. Here, the focal position of the laser beam is considered with the first surface 12 of the substrate 11 as 0 mm, and the direction of propagation of the laser beam (the direction from the first surface 12 of the substrate 11 into the interior of the substrate 11) as the positive direction.

[0075] Furthermore, in the manufacturing method according to one embodiment, it is preferable to apply room temperature air to the processing point in parallel with the irradiation of laser light. This suppresses the thermal influence between adjacent processing points and stabilizes the modification of the substrate 11.

[0076] Furthermore, in the wet etching after pretreatment, it is preferable to etch in such a way that no flat surfaces remain between adjacent aspherical lenses 13. This ensures that adjacent aspherical lenses 13 are continuous without flat surfaces, thereby suppressing the generation of zero-order light caused by flat surfaces.

[0077] <Examples> The above studies suggest that, in at least one row of aspherical lenses 13 arranged in a one-dimensional direction within the first surface 12 of the microlens array 10, if the average pitch of the aspherical lenses 13 is 30 μm or less and the average tilt is 0.300 or more, wide-angle and uniform diffusion can be achieved even when light of a small diameter is incident. The above effects will be verified below by examples, but this disclosure is not limited to these examples.

[0078] As an example, a microlens array sample was prepared with a reference pitch of 21 μm in the X direction and a reference pitch of 21 μm in the Y direction, and a total of 54,600 aspherical lenses arranged in 210 rows in the X direction and 260 rows in the Y direction. Here, the reference pitch refers to the target pitch value during fabrication. A glass substrate (D263, manufactured by Schott) with a thickness of 0.8 mm was used as the substrate.

[0079] In the example, the aspherical lens was fabricated by performing a pretreatment in which pulsed laser light was irradiated onto the substrate to modify a portion of the substrate's interior, followed by wet etching with hydrofluoric acid. The etching time was 60 minutes.

[0080] The laser irradiation conditions during pretreatment were as follows: wavelength 1064 nm, frequency 20 kHz, pulse width 10 ps, ​​power 0.7 W, and focal length 163 mm. The laser beam was irradiated onto the processing point while applying room temperature air.

[0081] Table 2 shows the average pitch, average slope, pitch variation, radius of curvature variation, depth variation, the maximum absolute value of the difference in diffusion profiles when the incident light diameter is changed, and the diffusion angle of the fabricated samples. For the average pitch, average slope, pitch variation, radius of curvature variation, and depth variation, a desired row of the aspherical lens array arranged in the X direction of the fabricated sample was selected, and the obtained values ​​are recorded in the "One-Dimensional Direction" column. For all arranged aspherical lenses, the obtained values ​​are recorded in the "In-Plane" column. The average pitch, average slope, pitch variation, radius of curvature variation, and depth variation were measured based on the cross-sectional profile of the aspherical lens obtained from the 3D shape of the aspherical lens measured using a laser microscope (Keyence VK-X3000).

[0082]

[0083] Furthermore, Figure 9 shows the diffusion profiles in the X direction when light with diameters of 0.2 mm, 0.4 mm, and 3 mm is incident on the sample of the example. Also, Figure 10 shows the difference in relative intensity between the diffusion profiles of 3 mm and 0.2 mm, and the difference in relative intensity between the diffusion profiles of 3 mm and 0.4 mm, for each diffusion angle in the sample of the example.

[0084] Figure 9 shows that in the embodiment where the average pitch and average slope in a desired row of aspherical lenses are within a specific range, a wide-angle and uniform diffusion of FOV of 40° or more can be achieved when light with an optical diameter of 0.2 mm, 0.4 mm, or 3 mm is incident.

[0085] Figure 10 shows that the microlens array in the embodiment in which the average pitch in a desired row of aspherical lenses is within a specific range can suppress changes in the diffusion profile even when light with small diameters of 0.2 mm and 0.4 mm is incident on it.

[0086] From the above, it can be seen that the microlens array of the embodiment achieves wide-angle and uniform diffusion even when light of a small diameter is incident on it, by setting the average pitch and average slope of a desired row of aspherical lenses to a specific range.

[0087] Although preferred embodiments have been described in detail above, the invention is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims.

[0088] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all illustrative to specifically illustrate the technology of this disclosure, and this disclosure is not limited to the illustrative figures. Furthermore, the connection relationships between the components are illustrative to specifically illustrate the technology of this disclosure, and are not limited to the connection relationships that realize the functions of this disclosure.

[0089] The microlens array and light source device according to this disclosure can suppress changes in the diffusion profile and achieve wide-angle and uniform diffusion even when light of a small diameter is incident on the microlens array, and can therefore be used in projection devices such as projectors, sensing devices such as LiDAR, etc. However, it is not limited to these, and the optical elements and light source devices according to the embodiments can be applied to a variety of fields that use optical methods.

[0090] This application claims priority based on Japanese Patent Application No. 2024-232812, filed on 27 December 2024, and incorporates all of its disclosures herein.

[0091] 10 Microlens array 11 Substrate 12 First surface 13 Aspherical lens 14 Vertex 20 Light source device 21 Light source Ls Diffuse light

Claims

1. A microlens array comprising a substrate having a first surface and a plurality of aspherical lenses arranged on the first surface, wherein the aspherical lenses are arranged in a one-dimensional direction, and in at least one row of the aspherical lenses, the average pitch of the aspherical lenses is 30 μm or less and the average tilt is 0.300 or more.

2. The microlens array according to claim 1, wherein the average pitch is 25 μm or less.

3. The microlens array according to claim 1, wherein the average gradient is 0.330 or greater.

4. The microlens array according to claim 1, wherein in at least one row of the aspherical lenses arranged in the one-dimensional direction of the first surface, the average pitch of the aspherical lenses is 5 μm or more.

5. The microlens array according to claim 1, wherein the field of view (FOV) is 40° or more when light with a wavelength of 660 nm is incident on it.

6. The microlens array according to claim 1, wherein the total light transmittance is 88% or more when light with a wavelength of 660 nm is incident on it.

7. The microlens array according to claim 1, wherein the aspherical lenses are continuous between adjacent aspherical lenses without any flat surfaces.

8. The microlens array according to claim 1, wherein in at least one row of the aspherical lenses arranged in the one-dimensional direction of the first surface, the variation in the radius of curvature of the aspherical lenses is 0.10 or more.

9. The microlens array according to claim 1, wherein in at least one row of the aspherical lenses arranged in the one-dimensional direction of the first surface, the variation in the lens depth of the aspherical lenses is 0.50 μm or more.

10. The microlens array according to claim 1, wherein the average pitch measured for all the aspherical lenses arranged on the first surface is 30 μm or less.

11. The microlens array according to claim 1, wherein the aspherical lens is a concave lens.

12. A light source device comprising a light source and a microlens array according to claim 1 disposed on the output side of the light source, wherein the microlens array diffuses and emits light from the light source.

Images