WO2024117157A1

WO2024117157A1 - Diffusion plate, light-emitting device, and sensor module

Info

Publication number: WO2024117157A1
Application number: PCT/JP2023/042670
Authority: WO
Inventors: 将山▲崎▼
Original assignee: 京セラ株式会社
Priority date: 2022-11-30
Filing date: 2023-11-29
Publication date: 2024-06-06

Abstract

This diffusion plate has a microlens array in which a plurality of convex lenses are regularly arranged, and has variation in the distribution of a carbon concentration among the plurality of convex lenses. The plurality of convex lenses may each have a high-concentration portion in which the carbon concentration is locally high in a range that includes a point of intersection of the optical axis of the convex lens with a reference line in the convex lens that intersects with the optical axis and is perpendicular to the optical axis. Among the plurality of convex lenses, the distribution of the carbon concentration along the reference line may have variation. The width on the reference line of the high-concentration portion may vary in accordance with the variation in the distribution of the carbon concentration.

Description

Diffusion plate, light-emitting device and sensor module

This disclosure relates to a diffuser, a light-emitting device, and a sensor module.

JP 2003-4907 A discloses a technique for reducing the occurrence of interference fringes in outgoing light by irregularly setting the spacing between the vertices of each lens in a microlens array that diffuses incoming light.

One aspect of the present disclosure is
A microlens array in which a plurality of convex lenses are regularly arranged is provided,
The carbon concentration distribution of the diffusion plate varies among the plurality of convex lenses.
Another aspect of the present disclosure is
The above-mentioned diffusion plate,
A light emitting element that emits light to be incident on the diffusion plate;
A light emitting device comprising:
Another aspect of the present disclosure is
The light-emitting device as described above;
a light receiving device for detecting incident light;
The sensor module includes:

1 is a schematic cross-sectional view of a sensor module including a light-emitting device using a diffusion plate according to an embodiment of the present invention. FIG. 4 is a contour map of the bottom side of the diffuser plate. FIG. FIG. 4 is a diagram illustrating a carbon concentration distribution of a convex lens. FIG. 13 is a diagram showing another example of the carbon concentration distribution of the convex lens. FIG. 13 is a diagram showing another example of the carbon concentration distribution of the convex lens.

Hereinafter, an embodiment will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a sensor module 100 including a light-emitting device 1 using a diffusion plate 10 of the present embodiment.

The sensor module 100 includes a light-emitting device 1 and a light-receiving device 2. The light-emitting device 1 and the light-receiving device 2 may be positioned side by side on a module substrate 3. The sensor module 100 is, for example, a photoelectric sensor that detects incident light emitted by the light-emitting device 1 and reflected by an object or the like and returns using the light-receiving device 2 to perform object detection, but is not limited to this.

The light-emitting device 1 includes a light-emitting element 15, a diffusion plate 10, and a housing 16. The light-emitting element 15 may be a surface-emitting laser, for example a vertical-cavity surface-emitting laser (VCSEL). The housing 16 may have a shape with a recess that is open on one side, for example a box shape, and is a package in which the light-emitting element 15 is located. The housing 16 also has signal lines and connection terminals for supplying power related to light emission to the light-emitting element 15 from the outside.

The diffusion plate 10 covers the open surface of the housing 16. The diffusion plate 10 diffuses the light emitted by the light-emitting element 15 and emits it to the outside. The diffusion plate 10 will be described later.

In addition to the light receiving element 22, the light receiving device 2 may include a substrate 21, an optical member 23, a support portion 24, and the like.
The light receiving element 22 may be, for example, a photodiode. The light receiving element 22 is capable of receiving incident light from above, and may be connected to a connection terminal on the substrate 21. The substrate 21 may have a signal line that outputs a signal according to the amount of received light to the outside, and one end of the signal line may be connected to the connection terminal.

The optical member 23 may include a lens, a filter, and the like. The optical member 23 focuses the light incident from above onto the entrance of the light receiving element 22. The optical member 23 may also include a bandpass filter that selectively passes light in the emission wavelength band of the light emitting element 15 and blocks light of other wavelengths. The other wavelengths of light that are blocked may include non-visible light such as infrared light. The support portion 24 supports the optical member 23. The support portion 24 may also function as a light blocking member that prevents light from entering the light receiving element 22 without passing through the optical member 23.

Next, the diffusion plate 10 will be described.
Fig. 2A is a contour map of the surface of the diffusion plate 10 of this embodiment as viewed from the bottom side, and Fig. 2B is a cross-sectional view of the diffusion plate 10 taken along the section line AA.
2A, the diffusion plate 10 has a microlens array 110 in which a plurality of convex lenses 11 are regularly arranged. Each of the convex lenses 11 protrudes downward (in the -Z direction) and diffuses light from a light-emitting element 15 located further below the microlens array 110 (in the -Z direction), emitting the light approximately evenly over a wider range. That is, the convex portions of the convex lenses 11 protrude toward the inner surface of the housing 16.

The microlens array 110 may be located on, but is not limited to, a glass substrate 120, which is a transparent flat plate, and has an uneven shape due to a transparent resin. The glass substrate 120 may be borosilicate glass. The thickness of the glass substrate 120 is, but is not limited to, about 100 to 1000 μm. The transparent resin may be, for example, an acrylic resin, an epoxy resin, a silicone resin, or the like. Alternatively, the diffusion plate 10 may be formed integrally with the microlens array 110 and the flat plate portion that corresponds to the glass substrate 120, by a transparent resin. The transparent resin layer may also contain carbon and a metal oxide. The metal oxide has a higher refractive index than the transparent resin, and is not limited to, but may be, for example, zirconium oxide, titanium oxide, cerium oxide, niobium oxide, or the like. The amount of these metal oxides may be, for example, 50% or less of the resin component by volume. As a result, the refractive index of the microlens array 110 may be, but is not limited to, about 1.5 to 2.0.

Here, the convex lenses 11 are arranged on the lattice points of a square lattice, but the arrangement is not limited to this.

As shown in FIG. 2B, the convex lens 11 may be a wide-angle lens type with a large concave/convex surface B compared to its width in a cross-sectional view passing through the apex/center. This makes it easier for the incident light from the light-emitting element 15 to enter the convex lens 11 at a large angle of incidence, and accordingly the direction of the light changes significantly at the lens surface. The light incident from each convex surface of the convex lens 11 does not need to converge to a single point. The upper surface on the +Z side of the glass substrate is flat, and light that enters the back surface of the diffuser plate 10 at a large angle of incidence is emitted to the outside from the surface of the diffuser plate 10 at an even larger exit angle. Light path L is shown as an example.

Here, if the multiple convex lenses 11 are uniform, the refraction pattern of the incident light, i.e., the output intensity distribution of the output light, becomes periodic, and interference fringes and the like are likely to occur in the output light. On the other hand, if the shapes of the convex lenses 11 are made different from each other, it takes time to manufacture them and is likely to affect the optical characteristics. For example, it becomes difficult to maintain the output intensity of the incident light with respect to the angle of incidence uniform. The convex lenses 11 of this embodiment have a variation in the internal carbon concentration distribution instead of the shape, thereby causing the distribution of the refractive index of each convex lens 11 to vary. In particular, the convex lenses 11 each include a high-concentration portion in which the carbon concentration is partially high inside, and the distribution of the high-concentration portion varies, resulting in a large difference in the optical path difference according to the carbon concentration distribution on the optical path, which is the path of the incident light. The high-concentration portion may cover the area through which the light incident from each portion of the surface of the convex lens 11 passes in common. In one embodiment, the high-concentration portion may be located at least near the center of the base (+Z side) of each convex lens 11, i.e., including the optical axis. As a result, the carbon concentration distribution on the optical path through which the light incident from the same relative position on the multiple convex lenses 11 passes is different. Therefore, the optical path length of each incident light is also different. As a result, the phase of the light exiting from the diffusion plate 10 is shifted, and the occurrence of interference fringes is reduced.
The term "varies" here does not mean that the carbon concentration distribution is different from one another in all of the convex lenses 11. However, the carbon concentration distribution may be different between the convex lenses 11 involved in the generation of interference fringes.

In addition, as described above, each convex lens 11 contains a metal oxide with a high refractive index, which further amplifies the difference in optical path length according to the difference in carbon concentration distribution. This allows the diffusion plate 10 to properly disperse the incident light with further reduced occurrence of interference fringes and the like.

FIG. 3 is a diagram showing a schematic diagram of the carbon concentration distribution of the convex lens 11. As shown in FIG.
The carbon concentration at the apex of the convex lens 11, i.e., at the cross section passing through the center in a plan view, does not need to be clearly divided into high and low regions. Overall, it is sufficient that the carbon concentration is relatively high in the dot region near the center of each convex lens 11, and the carbon concentration is relatively low near the connection part with other convex lenses 11 at the periphery of each convex lens 11. In one embodiment, a reference line S that intersects with the optical axis of each convex lens 11 and is perpendicular to them, and is on the root side (+Z side) of the height in the Z direction at the periphery of each convex lens 11, i.e., the point of height Zm where the value of the Z component is minimal, may be considered. That is, the reference line S may pass only through the convex lens 11. Along this reference line S, the width W2 of the high concentration part H2 in which the carbon concentration is higher than the reference carbon concentration by a predetermined percentage or more in a certain convex lens 11 may be wider than the width W1 of the high concentration part H1 in the other convex lens 11. Hereinafter, the high concentration parts are collectively referred to as high concentration parts H. The reference carbon concentration may be, for example, 75% or the like, which is the average carbon concentration in the multiple convex lenses 11 of the microlens array 110. The predetermined percentage may be, for example, 5%. The average carbon concentration may be an absolute value previously determined as a general product standard, or the average value along the reference line S of the product or the product may be used. Such a high-concentration portion H also spreads in the height direction (Z direction), and in particular, the point with the smallest Z coordinate, which is the upper end of the high-concentration portion H, is located on the tip side of the periphery of the convex lens 11, so that the length of the thick line portion of the optical path L2 passing through the high-concentration portion H is longer than that of the optical path L1. Therefore, the optical path length of the optical path L2 is longer than that of the optical path L1. In addition, the inclination of the optical paths L1 and L2 also changes slightly according to the increase in the refractive index.

Such variations in the high concentration portion H may occur not only in the spatial size of the high concentration portion H, i.e., in the width and height, but also in the carbon concentration itself. That is, the distribution of the carbon concentration in the high concentration portion H may vary for each convex lens 11. In one embodiment, the high concentration portion H may extend up and down across the position of height Zm where adjacent convex lenses 11 are connected at their peripheries. That is, the upper end, which is one end in the height direction of the high concentration portion H, may be located closer to the tip of the convex lens 11 than the periphery, and the lower end, which is the other end opposite to the one end, may be located closer to the base of the convex lens 11 than the periphery. In addition, the high concentration portion H may tend to be thicker on the base (+Z side) side of each convex lens 11, that is, the planar size may tend to increase the further from the tip.

4A and 4B are diagrams showing other examples of the carbon concentration distribution of the convex lens 11. In FIG.
As shown in Fig. 4A, the carbon concentration represented by the density of hatches may tend to increase further away from the convex surface of the convex lens 11, particularly the tip. In Fig. 4A, the carbon concentration is highest just below the apex of each convex lens 11, but the region with the highest carbon concentration may spread in the arrangement direction of the convex lenses 11. The concentration trend referred to here does not need to take into account the presence of fine local minimum/maximum portions of concentration. It may be to the extent that the concentration distribution trends match when the concentration distribution is approximated by a curve on a line or by a curved surface for each convex lens 11.

As shown in FIG. 4B, the high-concentration portion H may be connected at least in part to the high-concentration portion Hc, which is the base portion of the microlens array 110, which is a transparent resin layer in which multiple convex lenses 11 are connected.

The level of concentration referred to here is a level that is significant in breaking up the interference fringes, and is greater than manufacturing errors or variations. For example, in each convex lens 11, the length of the widths W1 and W2 of the high-concentration portion H, or the difference in the maximum carbon concentration on the reference line S within the widths W1 and W2, may be 5% or more greater within the microlens array 110. The upper limit of the variation is not limited as long as it is within a range in which light is appropriately transmitted, and may be, for example, 30% or less. The element concentration in a cross section may be determined, for example, from the concentration distribution in a certain cross section obtained by an energy dispersive X-ray spectrometer (EDS). Alternatively, a wavelength dispersive X-ray spectrometer (WDS) or the like may be used to measure the element concentration instead of an EDS.

These convex lenses 11 have a width and a height longer than the wavelength of the incident visible light. For example, the width and the height of the convex lenses 11 may each be 5 μm or more.
As a result, the light emission patterns of the convex lenses 11 do not overlap periodically, but are shifted, thereby reducing the occurrence of interference fringes.

When the microlens array 110 contains a metal oxide, the distribution of the metal oxide may be uniform within the microlens array 110. In other words, the concentration distribution of the metal oxide may not be correlated with the concentration distribution of carbon.

As is well known, a diffusion plate 10 having such an uneven structure of a microlens array 110 may be obtained by filling a transparent resin into a mold such as an electroforming mold or a secondary mold having the shape of a lens surface, pressing the resin to harden it, and then releasing the resin from the mold. For example, UV curing by irradiation with ultraviolet light may be used to harden the transparent resin.

At this time, the mold may also be made of a resin film, and ultraviolet light may be irradiated from the convex side of the transparent resin through the resin film. This causes the UV light to refract in the same way as the incident light from the light emitting element 15 during use. Since the refracted light passes mostly near the center of the convex lens 11, hardening proceeds preferentially in this vicinity. This causes a polymer to be formed near the center of the convex lens 11, and the carbon concentration is higher than in the surrounding area. Thus, a convex lens structure having the carbon concentration distribution disclosed herein is obtained. In order to clearly differentiate the carbon concentration distribution of this high concentration portion H, the irradiation time of the UV light may be appropriately varied. Also, multiple resin compositions may be applied to make it easier to produce variation in the carbon concentration distribution.

As described above, the diffusion plate 10 of this embodiment has a microlens array 110 in which multiple convex lenses 11 are regularly arranged. The multiple convex lenses 11 have variations in the distribution of carbon concentration. This causes the optical path length of light passing through each convex lens 11 to vary according to the distribution of carbon concentration. This makes it possible to reduce the periodic interference of light passing through the multiple convex lenses 11, resulting in interference fringes and the like. Furthermore, since there is no need to vary the shape of the convex lenses 11 itself, the effect of this variation on the optical characteristics can be more appropriately reduced.

Furthermore, each of the multiple convex lenses 11 may have a high concentration portion H where the carbon concentration is partially high, in a range including an intersection point with the optical axis on a reference line S within the convex lens 11 that intersects with the optical axis of the convex lens 11 and is perpendicular to the optical axis. The variation may exist at least on a reference line S within the convex lens 11 that intersects with the optical axis of the convex lens 11 and is perpendicular to the optical axis.
In this way, the presence of the high-density portion H near the optical axis located at the center of the convex lens 11 makes it easier for incident light to pass through the high-density portion H regardless of the incident position or angle, and the phase of the passing light is shifted according to the refractive index. Therefore, this diffusion plate 10 can more appropriately reduce the deterioration of the optical properties of the outgoing light and the occurrence of interference fringes.

The width of the high-concentration portion H on the reference line S may vary according to the variation in carbon concentration. In other words, the range of incident light passing through the high-concentration portion H varies, so the diffuser 10 can easily reduce the occurrence of interference fringes and the like.

Furthermore, the reference line S may be located closer to the base (+Z side) of the convex lens 11 than the periphery in the Z direction along the optical axis of the convex lens 11. By having the high-density portion H on the reference line S, i.e., closer to the base than the periphery, incident light at various angles of incidence on each convex lens 11 can easily pass through the high-density portion H. This allows the diffuser 10 to disperse the refraction direction of the incident light while reducing the effect on the optical characteristics, thereby further reducing the occurrence of interference fringes and the like.

The lower end of the high-concentration portion H may be located closer to the base (+Z side) than the periphery of the convex lens 11 in the Z direction along the optical axis of the convex lens 11. That is, the high-concentration portion H may extend toward the base in the direction along the optical axis of each convex lens 11. This makes it easier for incident light at various angles of incidence on each convex lens 11 to pass through the high-concentration portion H. This allows the diffuser 10 to disperse the refraction direction of the incident light while reducing the effect on the optical characteristics, thereby further reducing the occurrence of interference fringes and the like.

The upper end of the high-concentration portion H may be located on the tip side (-Z side) of the periphery of the convex lens 11 in the Z direction along the optical axis of the convex lens 11. That is, the high-concentration portion H may extend in the direction along the optical axis in each convex lens 11. This tends to lengthen the optical path that the light incident on each convex lens 11 takes through each high-concentration portion H, and this tends to cause variation. Thus, the diffuser 10 can further reduce the occurrence of interference fringes while reducing the effect on the optical characteristics.

Furthermore, the high-concentration portion H may have a larger planar size the farther it is from the tip of the convex lens 11 in the Z direction along the optical axis of the convex lens 11. In this way, the high-concentration portion H becomes thicker near the base of the convex lens 11, which is originally thick, so that incident light passes through the high-concentration portion H appropriately, and the optical path length varies according to this variation. This allows the diffuser 10 to reduce the occurrence of interference fringes and the like while reducing the impact on the optical characteristics.

The carbon concentration of the high concentration portion H may be higher the farther from the tip of the convex lens 11 in the Z direction along the optical axis of the convex lens 11. In other words, the carbon concentration distribution within the high concentration portion H does not need to be uniform and may be biased. By having a high carbon concentration especially near the base, incident light passes through the high concentration portion at a variety of angles. The optical path length of the incident light varies more efficiently depending on the length passing through this portion. This allows the diffuser 10 to reduce the occurrence of interference fringes while reducing the impact on the optical characteristics.

The high-density portion H may also have a high-density portion Hc that is at least partially connected between the convex lenses 11. Since the incident light always passes through the high-density portion Hc before being emitted to the outside of the diffuser plate 10, the emitted light tends to be emitted in the same direction.

The convex lens 11 may also contain a metal oxide with a higher refractive index than carbon. This further increases the refractive index of the convex lens 11, further accentuating the variation in optical path length according to the carbon concentration distribution. Therefore, the diffuser 10 can further reduce the occurrence of interference fringes while reducing the impact on the optical characteristics.

The light-emitting device 1 of this embodiment also includes the above-mentioned diffusion plate 10 and a light-emitting element 15 that emits light to be incident on the diffusion plate 10. With this type of light-emitting device 1, the light emitted by the light-emitting element 15 can be appropriately emitted to the outside while reducing the effect on the optical characteristics.

The sensor module 100 of this embodiment also includes the above-mentioned light-emitting device 1 and the light-receiving device 2 that detects incident light. In this sensor module 100, the light-emitting device 1 emits light while reducing the effect on the optical characteristics as described above, so the light-receiving device 2 that measures the reflected light of the emitted light can easily measure the appropriate amount of light to evaluate the measurement target.

The above-described embodiment is merely an example, and various modifications are possible.
For example, the size of the high concentration portion H and the distribution of the carbon concentration may be constant, i.e., isotropic, regardless of the orientation of the reference line S in each convex lens 11, or may have anisotropy. If the high concentration portion H and the carbon concentration distribution are anisotropic, the anisotropic characteristics, for example, the tendency of bias, may be different for each convex lens 11.

In the above embodiment, the convex lens is described as having at least a variation in the widths W1 and W2 of the high-concentration portion H on a straight line passing through the base side of the periphery, but this is not limited to this. The variation in the carbon concentration distribution may be evaluated at other positions and by other methods.

Furthermore, the range of the high concentration portion H and the corresponding reference line S are not limited to the above examples. If there is variation in the distribution of carbon concentration and the incident light from each surface position of the convex lens 11 passes through the range of variation, the occurrence of interference fringes and the like can be appropriately reduced.

Furthermore, the method for generating the high-concentration portion H in the convex lens 11 is not limited to the above-mentioned method. The high-concentration portion H may be generated by other methods.

In the above embodiment, the light emitting device 1 is described as a part of the sensor module 100, but the present invention is not limited to this. Only the light emitting device 1 may be used for trading separately from the light receiving device 2.
Furthermore, the diffusion plate 10 may be sold and used separately from the light emitting device 1 .

Furthermore, the combination of lenses and filters in the optical member 23, for example, the number, characteristics, and positional relationship of the filters, may be changed as necessary. In addition, the specific configurations, structures, materials, and manufacturing methods shown in the above embodiments may be changed as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention described in the claims and its equivalents.

This disclosure can be used in diffusers, light-emitting devices, and sensor modules.

REFERENCE SIGNS LIST 1 Light emitting device 2 Light receiving device 3 Module substrate 10 Diffuser 11 Convex lens 15 Light emitting element 16 Housing 21 Substrate 22 Light receiving element 23 Optical member 24 Support 100 Sensor module 110 Microlens array 120 Glass substrate H, H1, H2, Hc High density portion L, L1, L2 Light path S Reference line W1, W2 Width

Claims

A microlens array is provided in which a plurality of convex lenses are regularly arranged.
a diffusion plate having a carbon concentration distribution that varies among the plurality of convex lenses.
each of the plurality of convex lenses has a high-concentration portion having a locally high carbon concentration in a range including an intersection point with the optical axis on a reference line within the convex lens that intersects with the optical axis and is perpendicular to the optical axis;
2. The diffusion plate according to claim 1, wherein the carbon concentration distribution along the reference line varies among the plurality of convex lenses.
The diffusion plate according to claim 2 , wherein a width of the high-density portion on the reference line varies according to the variation.
The diffuser plate according to claim 2 or 3, wherein the reference line is located closer to the base side than the periphery of the convex lens in the direction along the optical axis.
The diffusion plate according to any one of claims 2 to 4, wherein the lower end of the high-concentration portion is located closer to the base than the periphery of the convex lens in the direction along the optical axis.
The diffuser plate according to any one of claims 2 to 5, wherein the upper end of the high-concentration portion is located on the tip side of the periphery of the convex lens in the direction along the optical axis.
The diffusion plate according to any one of claims 2 to 6, wherein the high-concentration portion has a larger planar size the farther it is from the tip of the convex lens in the direction along the optical axis.
The diffuser plate according to any one of claims 2 to 7, wherein the carbon concentration of the high concentration portion is higher the farther it is from the tip of the convex lens in the direction along the optical axis.
The diffusion plate according to any one of claims 2 to 8, wherein the high-concentration portions are connected between at least some of the multiple convex lenses.
The diffuser plate according to any one of claims 1 to 9, wherein the convex lens contains a metal oxide having a higher refractive index than carbon.
The diffusion plate according to any one of claims 1 to 10,
A light emitting element that emits light to be incident on the diffusion plate;
A light emitting device comprising:
A light emitting device according to claim 11;
a light receiving device for detecting incident light;
A sensor module comprising: