Diffuser plate, light-emitting device, and sensor module

Abstract

To provide a diffusion plate, a light-emitting device, and a sensor module capable of more appropriately suppressing influence on optical characteristics.SOLUTION: The diffusion plate includes a microlens array (110) in which a plurality of convex lenses are regularly arranged, and the plurality of convex lenses have a variation in carbon concentration distribution.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a diffuser plate, a light-emitting device, and a sensor module. [Background technology]

[0002] Patent Document 1 discloses a technique for reducing the occurrence of interference fringes in outgoing light by irregularly setting the intervals between the vertices of lenses in a microlens array that diffuses incident light. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-4907 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the vertex spacing of the microlens array is irregular, it may affect the optical characteristics. Therefore, the present invention provides a diffuser plate, a light-emitting device, and a sensor module that can more appropriately suppress the effect on the optical characteristics. [Means for solving the problem]

[0005] One aspect of the present disclosure is A microlens array is provided in which a plurality of convex lenses are regularly arranged, The carbon concentration distribution varies among the plurality of convex lenses. It is a diffusion plate. 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 described above; a light receiving device for detecting incident light; The sensor module includes: [Effects of the Invention]

[0006] According to the present disclosure, the influence on optical characteristics can be more appropriately suppressed. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a schematic cross-sectional view of a sensor module including a light-emitting device using the diffusion plate of the present embodiment. [Figure 2] 1A is a contour map of the bottom side of the diffuser plate, and FIG. 1B is a cross-sectional view thereof. [Figure 3] FIG. 10 is a diagram schematically illustrating the carbon concentration distribution of a convex lens. [Figure 4] FIG. 10 is a diagram showing another example of the carbon concentration distribution of the convex lens. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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 diffuser plate 10 of this embodiment.

[0009] 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 are positioned side by side on a module substrate 3. The sensor module 100 is, for example, a photoelectric sensor that detects reflected light (incident light) of light emitted by the light-emitting device 1 using the light-receiving device 2 to perform object detection, but is not limited to this.

[0010] The light-emitting device 1 includes a light-emitting element 15, a diffuser 10, and a housing 16. The light-emitting element 15 is a surface-emitting laser, such as a vertical-cavity surface-emitting laser (VCSEL). The housing 16 is a package having a shape with a recess with one open end, such as a box shape, 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 an external source.

[0011] 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 outputs the light to the outside. The diffusion plate 10 will be described later.

[0012] The light receiving device 2 includes a substrate 21, a light receiving element 22, an optical member 23, a support portion 24, and the like. The light receiving element 22 is, for example, a photodiode. The light receiving element 22 is capable of receiving incident light from above and is connected to a connection terminal on the substrate 21. The substrate 21 has a signal line that outputs a signal according to the amount of received light to the outside, and one end of the signal line is connected to the connection terminal.

[0013] The optical member 23 may include a lens, a filter, and the like. The optical member 23 focuses 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 wavelength band emitted by the light-emitting element 15 and blocks light of other wavelengths (including non-visible light such as infrared). 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.

[0014] Next, the diffusion plate 10 will be described. FIG. 2(a) is a contour map of the surface of the diffusion plate 10 of this embodiment as viewed from the bottom side, and FIG. 2(b) is a cross-sectional view taken along the cross-sectional line AA. 2(a), the diffuser 10 has a microlens array 110 in which a plurality of convex lenses 11 are regularly arranged. Each convex lens 11 protrudes downward (in the -z direction) and diffuses light from a light-emitting element 15 located further below (in the -z direction) the microlens array 110, 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.

[0015] The microlens array 110 is positioned on a transparent glass substrate 120 (flat plate), for example, but is not limited to, and has a textured surface formed by a transparent resin. The glass substrate 120 may be made of borosilicate glass. The thickness of the glass substrate 120 is, for example, about 100 to 1000 μm, but is not limited to this. The transparent resin may be, for example, an acrylic resin, an epoxy resin, or a silicone resin. Alternatively, the diffuser 10 may be formed such that the microlens array 110 and the flat plate portion corresponding to the glass substrate 120 are integrally formed from 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 particularly limited, but examples thereof include zirconium oxide, titanium oxide, cerium oxide, and niobium oxide. The amount of these metal oxides is, for example, 50% or less by volume of the resin component. As a result, the refractive index of the microlens array 110 is, for example, about 1.5 to 2.0, but is not particularly limited thereto.

[0016] Here, the convex lenses 11 are arranged on the lattice points of a square lattice, but the arrangement is not limited to this.

[0017] As shown in FIG. 2(b), the convex lens 11 is a wide-angle lens type with a large concave / convex shape compared to its width in a cross-sectional view (passing through the vertex / center). This makes it easier for incident light from the light-emitting element 15 to enter the convex lens 11 at a large angle of incidence, and the direction of the light changes significantly on the lens surface accordingly. 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 angle of emission. Light path L is shown as an example.

[0018] If the multiple convex lenses 11 were uniform, the refraction pattern of the incident light, i.e., the intensity distribution of the output light, would be periodic, making interference fringes more likely to occur in the output light. On the other hand, different shapes of the convex lenses 11 would require more time and effort to manufacture and would likely affect the optical characteristics. For example, it would be difficult to maintain uniformity in the output intensity versus the angle of incidence of the incident light. The convex lenses 11 of this embodiment vary in the internal carbon concentration distribution instead of the shape, thereby varying the refractive index distribution of each convex lens 11. In particular, each convex lens 11 contains high-concentration portions with locally high carbon concentrations. The variation in the distribution of these high-concentration portions results in significant differences in the optical path difference according to the carbon concentration distribution along the path (optical path) of the incident light. In particular, it is preferable that the high-concentration portions cover the area through which light incident from each portion of the surface of the convex lenses 11 commonly passes. Here, the high-concentration portions are located at least near the center (directly below the optical axis) of the base (+Z side) of each convex lens 11. As a result, the carbon concentration distribution along the optical path through which each light beam passes differs when it is incident from the same relative position on the multiple convex lenses 11. Therefore, the optical path length of each incident light beam also differs. As a result, the phase of the light beam emitted from the diffuser plate 10 is shifted, suppressing the occurrence of interference fringes. 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, it is preferable that the carbon concentration distribution is different from one another in the convex lenses 11 that are involved in the generation of interference fringes.

[0019] Furthermore, 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, thereby allowing the diffuser 10 to further suppress the occurrence of interference fringes and appropriately disperse incident light.

[0020] FIG. 3 is a diagram schematically showing the carbon concentration distribution of the convex lens 11. As shown in FIG. The carbon concentration in a cross section passing through the apex (center) of each convex lens 11 does not need to be clearly divided into high and low regions. Overall, the carbon concentration tends to be relatively high (hatched region) near the center of each convex lens 11 and relatively low near the periphery (the junction with other convex lenses 11). Here, we consider a reference line S (a line within the convex lens 11) that intersects with and is perpendicular to the optical axis of each convex lens 11 and is located above (toward the base) the point (height Zm) where the height in the z direction (i.e., the z component) at the periphery of each convex lens 11 is minimal, i.e., passes only through the interior of the convex lens 11. Along this reference line S, the width W2 of a region (high-concentration portion H2) where the carbon concentration is higher by a predetermined percentage (e.g., 5%) or more than the average carbon concentration (e.g., 75%) in a certain convex lens 11 (microlens array 110) is wider than the width W1 of the high-concentration portion H1 in the other convex lenses 11. The average carbon concentration may be a predetermined absolute value as a general product standard, or may be an average value for the product or even along the reference line S of the product. These high-concentration portions H1 and H2 (hereinafter, the high-concentration portions will be collectively referred to as high-concentration portion H) also extend in the height direction (z direction). In particular, the upper end (the point with the smallest Z coordinate) of high-concentration portion H is located closer to the tip than the periphery of convex lens 11. Therefore, the length of optical path L2 passing through high-concentration portion H is longer than that of optical path L1 (shown by a bold line). Therefore, the optical path length of optical path L2 is longer than that of optical path L1. Furthermore, the slopes of optical paths L1 and L2 change slightly as the refractive index increases.

[0021] Such variations in the high-concentration portions H may occur not only in the spatial size (width and height) of the high-concentration portions H, but also in the carbon concentration itself. That is, the distribution of carbon concentration in the high-concentration portions H may vary for each convex lens 11. Here, the high-concentration portions H extend vertically across the connection positions (peripheries; height Zm) of the respective convex lenses 11. That is, one end (upper end) of the high-concentration portions H in the height direction is closer to the tip of the convex lens 11 than the peripheries, and the other end (lower end) is closer to the base of the convex lens 11 than the peripheries. Furthermore, the high-concentration portions H may tend to become thicker at the base (+z side) of each convex lens 11 (the planar size increases the farther from the tip).

[0022] FIG. 4 is a diagram showing another example of the carbon concentration distribution of the convex lens 11. In FIG. As shown in FIG. 4(a), the carbon concentration, represented by the density of the hatching, may tend to increase further away from the convex surface of the convex lenses 11, particularly as the distance from the tip increases. In FIG. 4(a), the carbon concentration is highest directly below the apex of each convex lens 11, but the region with the highest carbon concentration may extend in the direction in which the convex lenses 11 are arranged. The concentration trend referred to here does not need to take into account the presence of small, locally small minimum / maximum concentration areas. It may be sufficient that the concentration distribution trend matches when the concentration distribution is approximated by a curve on a certain line or by a curved surface for each convex lens 11.

[0023] As shown in FIG. 4(b), the high-concentration portion H may be at least partially connected (high-concentration portion Hc) at the base of the transparent resin layer (microlens array 110) where the multiple convex lenses 11 are connected.

[0024] The difference in concentration here is significant enough to break up the interference fringes and is significantly larger than manufacturing errors (variations). For example, in each convex lens 11, the difference in 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 is 5% or more within the microlens array 110. The upper limit of the variation is not limited as long as it is within a range that allows appropriate light transmission, and the difference may be, for example, 30% or less. The element concentration in a cross section can be determined from the concentration distribution in a certain cross section obtained, for example, by an energy dispersive X-ray spectrometer (EDS). Alternatively, a wavelength dispersive X-ray spectrometer (WDS) or the like may be used instead of an EDS to measure the element concentration.

[0025] These convex lenses 11 have widths and heights longer than the wavelength of the incident light (visible light).For example, the width and height of the convex lenses 11 are each 5 μm or more. As a result, the light emission patterns of each convex lens 11 do not overlap periodically, but rather shift, thereby suppressing the occurrence of interference fringes.

[0026] 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.

[0027] As is well known, the diffusion plate 10 having such a concave-convex structure of the microlens array 110 can be obtained by filling a transparent resin into a mold such as an electroforming mold or a secondary mold having the shape of the lens surface, pressing the resin to harden it, and then releasing the resin from the mold. For example, ultraviolet light irradiation (UV curing) is used to harden the transparent resin.

[0028] At this time, the mold is also made of a resin film, and ultraviolet light is irradiated through the resin film from the convex side of the transparent resin, causing the UV light to refract in the same manner as incident light from the light-emitting element 15 during use. Since the refracted light passes mostly near the center of the convex lens 11, curing proceeds preferentially in this vicinity. As a result, a polymer is formed near the center of the convex lens 11, and the carbon concentration increases compared to the peripheral region. Thus, a convex lens structure having the carbon concentration distribution of the present disclosure is obtained. The irradiation time of UV light may be varied as appropriate to clearly differentiate the carbon concentration distribution of this high-concentration portion H. Furthermore, multiple resin compositions may be used to facilitate variation in the carbon concentration distribution.

[0029] As described above, the diffuser 10 of this embodiment has a microlens array 110 in which a plurality of convex lenses 11 are regularly arranged. The plurality of convex lenses 11 have variations in the distribution of carbon concentration. As a result, the optical path length of light passing through each of the convex lenses 11 varies depending on the distribution of carbon concentration. This makes it possible to prevent the light passing through the plurality of convex lenses 11 from periodically interfering with each other and causing interference fringes and the like. Furthermore, since there is no need to vary the shape of the convex lenses 11, the effect of such variations on the optical characteristics can be more appropriately suppressed.

[0030] Each of the plurality of convex lenses 11 has a high concentration portion H where the carbon concentration is locally high, in a range including the 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 exists 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. The presence of the high-density portion H near the center (optical axis) 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 of the high-density portion H. Therefore, this diffuser plate 10 can more appropriately suppress the deterioration of the optical properties of the outgoing light and the occurrence of interference fringes.

[0031] Furthermore, the width of the high-concentration portion H on the reference line S varies depending on the variation in carbon concentration. That is, the range of incident light passing through the high-concentration portion H varies, so the diffuser 10 can easily suppress the occurrence of interference fringes and the like.

[0032] Furthermore, the reference line S is located (z component) closer to the base of the convex lens 11 than the periphery of the lens 11 in the direction (z direction) along the optical axis of the lens 11. The presence of the high-density portions H on the reference line S, i.e., closer to the base than the periphery, makes it easier for light incident on each lens 11 at various angles of incidence to pass through the high-density portions H. This allows the diffuser 10 to disperse the refraction direction of the incident light while minimizing the effect on the optical characteristics, thereby more reliably suppressing the occurrence of interference fringes and the like.

[0033] Furthermore, the lower end of the high-concentration portion H is located closer to the base (+z side) than the periphery of the convex lens 11 in the direction along the optical axis of the convex lens 11 (z direction). That is, the high-concentration portion H extends toward the base of each convex lens 11 in the direction along the optical axis. This makes it easier for light incident on each convex lens 11 at various angles of incidence to pass through the high-concentration portion H. This allows the diffuser 10 to disperse the refraction direction of incident light while minimizing the impact on optical characteristics, thereby more reliably suppressing the occurrence of interference fringes and the like.

[0034] Furthermore, the upper ends of the high-concentration portions H are located closer to the tip (-z side) than the periphery of the convex lenses 11 in the direction along the optical axis of the convex lenses 11 (z direction). That is, the high-concentration portions H 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 vary. Therefore, the diffuser 10 can more reliably suppress the occurrence of interference fringes and the like while minimizing the impact on optical characteristics.

[0035] 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 direction along the optical axis of the convex lens 11 (z direction). In this way, the high-concentration portion H becomes thicker near the base of the convex lens 11, which is already thick, so that incident light passes through the high-concentration portion H appropriately, and the optical path length varies depending on the variation in the thickness. This allows the diffuser 10 to suppress the occurrence of interference fringes and the like while minimizing the impact on the optical characteristics.

[0036] Furthermore, the carbon concentration in the high-concentration portion H may be higher the farther from the tip of the convex lens 11 in the direction along the optical axis of the convex lens 11 (z direction). 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 particularly high carbon concentration near the base, incident light at various angles passes through the high-concentration portion. 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 suppress the occurrence of interference fringes while minimizing the impact on optical characteristics.

[0037] Furthermore, the high-density portions H may have at least a portion (high-density portions Hc) that is connected between the convex lenses 11. Since incident light always passes through the high-density portions Hc before being emitted to the outside of the diffuser plate 10, the emitted light tends to be emitted in the same direction.

[0038] Furthermore, the convex lens 11 may contain a metal oxide having a higher refractive index than carbon. This further increases the refractive index of the convex lens 11, thereby emphasizing the variation in optical path length according to the carbon concentration distribution. Therefore, the diffuser 10 can further suppress the occurrence of interference fringes while minimizing the impact on the optical characteristics.

[0039] Furthermore, the light-emitting device 1 of this embodiment includes the above-described diffuser plate 10 and a light-emitting element 15 that emits light to be incident on the diffuser plate 10. Such a light-emitting device 1 allows the light emitted by the light-emitting element 15 to be appropriately emitted to the outside while minimizing the influence on the optical characteristics of the light-emitting element.

[0040] The sensor module 100 of this embodiment includes the above-described light-emitting device 1 and a light-receiving device 2 that detects incident light. In this sensor module 100, the light-emitting device 1 emits light while minimizing the effect on optical characteristics as described above, so the light-receiving device 2 that measures the reflected light of the emitted light can easily measure an appropriate amount of light and evaluate the measurement target.

[0041] The above-described embodiment is merely an example, and various modifications are possible. For example, the size and concentration (distribution of carbon concentration) of the high-concentration portion H 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 there is anisotropy, it is more preferable that the anisotropic characteristics (bias tendency) differ for each convex lens 11.

[0042] In the above embodiment, the high-concentration portion H has at least a variation in widths W1 and W2 on a line passing through the base side of the periphery of the convex lens, but this is not limiting. The variation in the carbon concentration distribution may be evaluated at other positions or by other methods.

[0043] Furthermore, the range of the high-concentration portion H and the corresponding reference line S are not limited to those exemplified above. If there is variation in the distribution of carbon concentration and the structure is such that incident light from each surface position of the convex lens 11 passes through the range of variation, it is possible to appropriately suppress the occurrence of interference fringes and the like.

[0044] Furthermore, the method for generating the high-density portion H in the convex lens 11 is not limited to the above-described method, and the high-density portion H may be generated by other methods.

[0045] In the above embodiment, the light emitting device 1 is described as a part of the sensor module 100, but this is not limiting. The light emitting device 1 may be used for transactions separately from the light receiving device 2. Furthermore, the diffusion plate 10 may be sold and used separately from the light emitting device 1.

[0046] Furthermore, the combination (number, characteristics, positional relationship) of lenses and filters in the optical member 23 may be changed as necessary. The specific configurations, structures, materials, and manufacturing methods shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention set forth in the claims and their equivalents. [Explanation of symbols]

[0047] 1 Light-emitting devices 2. Light receiving device 3 Module Board 10 Diffuser 11 Convex lens 15 Light-emitting element 16 Case 21 PCB 22 Photodetector 23 Optical Components 24 Support part 100 Sensor Module 110 Microlens Array 120 Glass substrate H, H1, H2, Hc high concentration area L, L1, L2 optical path S reference line W1, W2 width

Claims

1. A microlens array is provided in which a plurality of convex lenses are regularly arranged, The carbon concentration distribution varies among the plurality of convex lenses. Diffuser.

2. each of the plurality of convex lenses has a high-concentration portion where the carbon concentration is locally high 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 diffuser plate according to claim 1, wherein the carbon concentration distribution along the reference line varies among the plurality of convex lenses.

3. The width of the high-density portion on the reference line varies according to the variation. The diffuser plate according to claim 2.

4. 3. The diffuser plate according to claim 2, wherein the reference line is located closer to the base of the convex lens than the periphery of the convex lens in the direction along the optical axis.

5. 3. The diffuser plate according to claim 2, wherein the lower end of the high-density portion is located closer to the base of the convex lens than the periphery of the convex lens in the direction along the optical axis.

6. 3. The diffuser plate according to claim 2, wherein the upper end of the high-density portion is located on the tip side of the periphery of the convex lens in the direction along the optical axis.

7. The diffuser plate according to claim 2 , wherein the high-density portion has a planar size that increases as it moves away from the tip of the convex lens in the direction along the optical axis.

8. 3. The diffuser plate according to claim 2, wherein the carbon concentration of the high concentration portion increases with increasing distance from the tip of the convex lens in the direction along the optical axis.

9. 3. The diffuser plate according to claim 2, wherein the high-density portion is connected between at least some of the plurality of convex lenses.

10. The diffuser plate according to claim 1 , wherein the convex lenses contain a metal oxide having a refractive index higher than that of carbon.

11. 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:

12. A light emitting device according to claim 11; a light receiving device for detecting incident light; A sensor module comprising:

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