Patent Application
20220308271
This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2021-048750, filed on Mar. 23, 2021, the entire contents of which are incorporated herein by reference.
The present invention relates to an optical element and a manufacturing method for the optical element.
In recent years, there has been an increase in the need for a fingerprint authentication function that is personal authentication using biometric information in a portable electronic device such as a smartphone. In particular, there is known a technique in which an optical fingerprint authentication sensor is arranged below a display unit of the portable electronic device, and thus the fingerprint authentication can be performed only by touching the display unit of the portable electronic device (see, for example, Patent Documents 1 and 2). In this optical fingerprint authentication sensor, scattered light from the fingertip is collected by a microlens array (optical element) below the display unit, and detection by an image sensor is performed to acquire the fingerprint pattern.
Then, to reduce noise light that passes through the microlens array and is incident on the image sensor and to increase the accuracy of image detection, it is necessary to form a light shielding film in the peripheral portion of each lens component (optical component) in the microlens array. However, since the accuracy of the formation position of the light shielding film is not sufficiently high, a gap between an end portion of the light shielding film and the lens component is necessarily sufficiently widened to prevent the light shielding film from reaching the lens component, and there is a disadvantage that noise light enters the microlens array from the gap.
The technology of the present disclosure has been made in view of the above circumstances, and an object thereof is to provide a technique for suppressing stray light incident on an optical component from a gap between the optical component and a light shielding film and improving the imaging performance of the optical element.
To solve the problems described above, an optical element according to the present disclosure is configured such that a light shielding film is provided around one or more optical components arranged at a base material portion having a substantially flat plate shape in a manner that a predetermined gap region is formed with respect to at least a portion of an outer periphery of the optical component, and a surface roughened portion having a surface roughness greater than a surface roughness of another region in the base material portion is provided in at least a portion of the gap region.
More particularly, an optical element according to the present disclosure includes one or more optical components arranged on at least one side of a base material portion having a substantially flat plate shape, a light shielding film provided around the optical component on a surface at which the one or more optical components of the base material portion are provided in a manner that a predetermined gap region is formed with respect to at least a portion of an outer periphery of the optical component, and a surface roughened portion provided in at least a portion of the gap region and having a surface roughness greater than a surface roughness of another region in the base material portion.
Here, the light shielding film may include an opening formed to surround at least a portion of the outer periphery of the optical component via the gap region, and the gap region may be a region sandwiched between a peripheral edge of the opening and the outer periphery of the optical component.
Further, the surface roughened portion may be also provided under the light shielding film on the surface at which the one or more optical components of the base material portion are provided.
Further, the surface roughened portion may be provided at a substantially entire surface excluding the optical component, on the surface at which the one or more optical components of the base material portion are provided.
A width of the gap region in a radial direction may be from 0.1 μm to 100 μm.
A manufacturing method for an optical element according to the present disclosure includes: integrally molding a base material portion having a substantially flat plate shape, one or more optical components arranged at a surface of the base material portion, and a surface roughened portion provided in a region surrounding the optical component, the surface roughened portion including a surface roughened, and then forming a light shielding film to surround, via a predetermined gap region, at least a portion of the outer periphery of the optical component, in which the surface roughened portion is provided in at least a portion of the gap region.
More specifically, an manufacturing method for an optical element according to the present disclosure includes: integrally molding a base material portion having a substantially flat plate shape, one or more optical components arranged at a surface of the base material portion, and a surface roughened portion provided in a region surrounding the optical component on the surface of the base material portion and including a surface roughened, and forming, after the molding, a light shielding film to surround, via a predetermined gap region, at least a portion of an outer periphery of the optical component on a surface at which the one or more optical components of the base material portion are provided, in which the surface roughened portion is provided in at least a portion of the gap region.
Here, the manufacturing method for an optical element may include integrally molding a base material portion having a substantially flat plate shape, and one or more optical components arranged at a surface of the base material portion, forming a surface roughened portion including a surface roughened in a region surrounding the optical component on the surface of the base material portion, and forming a light shielding film to surround, via a predetermined gap region, at least a portion of an outer periphery of the optical component on a surface at which the one or more optical components of the base material portion are provided, in which the surface roughened portion may be provided in at least a portion of the gap region.
Further, in the molding, the surface roughened portion may be molded using a surface roughened mold, by blasting in advance.
Further, in the forming of the surface roughened portion, the surface roughened portion may be formed by blasting.
Further, the light shielding film may include an opening formed to surround at least a portion of the outer periphery of the optical component via the gap region, and the gap region may be a region sandwiched between a peripheral edge of the opening and the outer periphery of the optical component.
Further, the surface roughened portion may be also provided under the light shielding film on the surface at which the one or more optical components of the base material portion are provided.
Further, the surface roughened portion may be provided at a substantially entire surface excluding the optical component, on the surface at which the one or more optical components of the base material portion are provided.
A width of the gap region in a radial direction may be from 0.1 μm to 100 μm.
Note that, in the present disclosure, as long as possible, techniques for solving the above-mentioned problems can be used in combination.
According to the present disclosure, a technique that can suppress stray light incident on an optical element from a gap between the optical component and a light shielding film and improve the imaging performance of the optical element can be provided.
Hereinafter, a microlens array and a manufacturing method for the microlens array according to an embodiment of the present disclosure will be described with reference to the drawings. Note that each of the configurations, combinations thereof, and the like in the embodiment are an example, and various additions, omissions, substitutions, and other changes may be made as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited by the embodiments and is limited only by the claims.
The under-display type fingerprint authentication apparatus 100 includes a cover glass 101 in a display of the portable electronic device and an OLED (Organic Light Emitting Diode) 102 arranged in a lower layer of the cover glass 101, for example. This OLED 102 includes a light-emitting element (not illustrated), and has a light-emitting function. In addition, a microlens array 103 arranged below the OLED 102, and an image sensor 104 that captures an image of a fingerprint by detecting light collected by the microlens array 103 are included.
The microlens array 103 has a plurality of lens components 1030a as an optical component. The lens components 1030a are aligned one dimensionally or two dimensionally on a base material portion 103b having a substantially plate shape. The arrangement number and the alignment position of the lens components 1030a are not particularly limited, and are determined according to the size of the imaging target S and the size of the image sensor 104.
Each lens component 1030a collects, on the image sensor 104, light emitted from the OLED 102 and scattered by the imaging target S, for example. The image sensor 104 has an imaging plane at which a plurality of imaging elements are aligned one dimensionally or two dimensionally, and converts the collected light into an electric signal to generate a captured image. The image sensor 104 outputs the generated captured image to the information processing device (not illustrated). As the image sensor 104, for example, in addition to a photodiode, a CCD, a CMOS, an organic EL, a TFT, etc. may be used. By using the optical system including the microlens array 103 in the fingerprint authentication apparatus 100, the apparatus can be further miniaturized.
The function and accuracy of the microlens array 103 vary depending on the shape (spherical, aspherical, cylindrical, hexagonal, etc.) of each lens component 1030a constituting the lens region 103a, the size of the lens component 1030a, the arrangement of the lens components 1030a, the pitch between the lens components 1030a, etc. The lens component 1030a in the microlens array 103 corresponds to an optical component of the present disclosure. The material of the microlens array 103 can include a resin material such as polycarbonate, PMMA, and cyclo-olefin copolymerization, but the type of material is not particularly limited.
Further, a light shielding film 1030b is provided around the lens component 1030a of the lens region 103a in the microlens array 103. In the fingerprint authentication apparatus 100, the light shielding film 1030b blocks light scattered by the fingertip as the imaging target S and incident on a portion excluding the lens component 1030a in the microlens array 103, and removes noise components (also referred to as noise light) in light reaching the image sensor 104. This improves the S/N ratio of the captured image generated by the image sensor 104, and can improve image quality.
More specifically, a liquid photoresist material is applied to the surface of the base material portion 103b at which the lens components 1030a are formed, and exposure is performed in a state where, for example, a portion excluding the lens component 1030a is covered with a photomask 200. Then, by removing the exposed portion of the photoresist material by an etching process, the light shielding film 1030b made of the photoresist material is formed at a portion excluding the lens component 1030a in the base material portion 103b.
The light shielding film 1030b has an opening 1030c formed to surround the outer periphery of the lens component 1030a from the periphery. Preferably, a peripheral edge portion 1030d of the opening 1030c and the outer periphery of the lens component 1030a accurately match. However, in this case, due to the positional deviation between the microlens array 103 and the photomask 200 when forming the light shielding film 1030b, as illustrated in
On the other hand, in the related art, the size of the opening 1030c in the light shielding film 1030b is set to be larger than the outer periphery of the lens component 1030a, and thus the light shielding film 1030b does not ride on the lens component 1030a even when the positional deviation between the microlens array 103 and the photomask 200 occurs. However, as a result, as illustrated in
Next,
More specifically, in a mold for resin-molding the microlens array 1, a portion corresponding to the lens component 1a in the upper mold is covered with a mask, and then the surface is roughened by a blasting technique in which air containing an abrasive is made to collide. In the manufacturing process of the microlens array 1, the base material portion 1b, the lens component 1a, and the surface roughened region 1c are integrally molded with the resin molding.
After that, the light shielding film 2 is formed by the above-mentioned photolithography technique. Here, the outer periphery 1d of the lens component 1a may be defined as an intersection line between the lens surface and the surface of the base material portion 1b, or may be defined as a circumferential portion having an effective diameter that functions as a lens in the lens component 1a. In addition, the width of the gap region in the radial direction (i.e., the distance between the peripheral edge portion 2b of the opening 2a of the light shielding film 2 and the outer periphery 1d of the lens component 1a) may be from 0.1 μm to 100 μm. Preferably, the width may be from 0.5 μm to 50 μm. More preferably, the width may be from 1 μm to 30 μm.
Additionally, the region to be roughened as the surface roughened region 1c is preferably the entire region of the gap region which is a region sandwiched between the peripheral edge portion 2b of the opening 2a of the light shielding film 2 and the outer periphery 1d of the lens component 1a. However, the surface roughened region 1c may be formed for a portion of the gap region. In addition, the surface roughened region 1c may be formed on the lower side of the light shielding film 2. The surface roughened region 1c may be formed at an entire surface excluding the surface of the lens component 1a, on the surface of the base material portion 1b at which the lens component 1a is provided. Further, the surface roughened region 1c is defined as a region having a surface roughness greater than that of the other region in the base material portion 1b; however, the other region in the base material portion 1c may be the opposite surface or the side surface in the base material portion 1c, in a case where the surface roughened region 1c is formed at the entire surface excluding the surface of the lens component 1a, on the surface of the base material portion 1b at which the lens component 1a is provided.
Next, in S02, the light shielding film 2 is formed by the photolithography technique. At this time, the peripheral edge portion 2b of the opening 2a of the light shielding film 2 has a sufficient gap with respect to the outer periphery 1d of the lens component 1a, and in S02, even when the positional deviation of the microlens array 1 and the photomask 200 occurs, the light shielding film 2 does not ride up on the surface of the lens component 1a. Further, since the surface roughened region 1c is formed at the gap region between the outer periphery 1d of the lens component 1a and the peripheral edge portion 2b of the opening 2a of the light shielding film 2, the image sensor 104 can be suppressed from being irradiated directly with the noise light incident on the gap region and without being scattered. As a result, the decrease in the S/N ratio due to the noise light of the image sensor 104 and the decrease in image quality can be suppressed, and the accuracy of the fingerprint authentication can be enhanced. The process of S02 corresponds to the forming of the light shielding film in the present embodiment.
Note that in the manufacturing method for the microlens array 1, the base material portion 1b, the lens component 1a, etc. are integrally molded in the molding of the resin, and then a portion excluding the lens component 1a in the microlens array 1 may be roughened by the blasting technique. This process corresponds to the blasting in the present embodiment.
Next, in S13, the light shielding film 2 is formed at the microlens array 1 by the photolithography technique. The process of S13 corresponds to the forming of the light shielding film in the present embodiment. Also in this case, a sufficiently wide gap region is secured between the peripheral edge portion 2b of the opening 2a of the light shielding film 2 and the outer periphery 1d of the lens component 1a, and even when the positional deviation of the microlens array 1 and the photomask 200 occurs during the formation of the light shielding film 2, the light shielding film 2 does not ride on the surface of the lens component 1a. Further, since the surface roughened region 1c is formed at the gap region between the outer periphery 1d of the lens component 1a and the peripheral edge portion 2b of the opening 2a of the light shielding film 2, the image sensor 104 is suppressed from being irradiated with the noise light incident on the gap region and component without being scattered.
In this example as well, since the surface roughened region 1c is formed at the gap region between the outer periphery 1d of the lens component 1a and the peripheral edge portion 2b of the opening 2a of the light shielding film 2, the image sensor 104 is suppressed from being irradiated with the noise light incident on the gap region and without being scattered. Additionally, the surface roughened region 10c is also formed at the lower surface of the microlens array 10, and thus internal reflection in the microlens array 10 can be suppressed. As a result, the occurrence of flare or ghost due to the noise light in the microlens array 10 can be suppressed.
Note that a microlens array having a function equivalent to that of the microlens arrays 1 and 10 described in the present embodiment may be used as an optical system for image capturing other than fingerprint authentication, face authentication in security equipment, or space authentication in vehicles or robots. Further, in the present embodiment, the material of the microlens arrays 1 and 10 has been described on the premise that the material is a resin material, but the material of the microlens arrays 1 and 10 is not limited thereto. Other materials such as glass may be used. For example, a combination of a resin material and a glass material may be a combination of a structure in which a lens array of resin is affixed to a glass material. Also, glass molding may be employed instead of resin molding for the manufacturing method for the microlens array.
Also in the above embodiments, an example has been described in which the optical element is a microlens array having a lens component as an optical component, but the technique of the present disclosure may be applied to other optical elements of the microlens array. For example, it can be applied to an optical element including a diffraction grating component, a prism component, a mirror component, etc. as an optical component. In addition, in the embodiment described above, an example has been described using the blasting technique as a method for surface roughening, but the method for surface roughening is not limited thereto. A method of roughening the surface by altering the metal surface of the mold or the resin surface of the microlens array by a chemical method, a thermal method, or an optical method such as a laser may be used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-048750 | Mar 2021 | JP | national |
