Microlens array module and method for manufacturing same

Abstract

The present invention relates to a microlens array module and a method for manufacturing same. The microlens array module comprises: first mirrors spaced apart from each other by a first gap on a first surface of a transparent substrate onto which light is incident; second mirrors disposed so as to reflect light traveling through a right-side region from the center of the first gap toward a first mirror positioned adjacent to the right; third mirrors disposed so as to reflect light traveling through a left-side region from the center of the first gap toward a first mirror positioned adjacent to the left; and microlenses arranged on a second surface of the transparent substrate opposite the first mirrors to focus the incident light.

Description

Micro lens array module and manufacturing method thereof

[0001] The present invention relates to a micro lens array module and a method for manufacturing the same, and more particularly, to a micro lens array module and a method for manufacturing the same that improves image resolution while having an aberration correction effect. This research was conducted with support from the National Research Facility Equipment Advancement Support (R&D) - Intelligent Optical Module Research Center Facility Equipment Advancement Project (Project Unique Number: 1711200897, Subproject Number: PG2023003).

[0002] In general, an image sensor refers to a semiconductor device that detects optical images corresponding to subject information and converts them into electrical image signals.

[0003] These image sensors use light-sensitive elements, such as photodiodes, to detect light, and the resolution of the image is determined by the number of light-sensitive elements. However, as various imaging devices have recently developed toward miniaturization and high resolution, the image sensors used in imaging devices are also changing toward miniaturization, higher resolution, and higher integration. Due to this miniaturization, higher resolution, and higher integration of image sensors, the number of pixels per unit area of ​​the image sensor has significantly increased, and accordingly, the size of the unit pixel has decreased.

[0004] As the unit pixel size decreases, the area of ​​the light-sensitive element that receives light within the image sensor inevitably also decreases, and this reduction in the area of ​​the light-sensitive element ultimately leads to a decrease in photosensitivity. Accordingly, recently, many studies have been conducted on light-concentrating technologies that divert the path of light incident outside the photosensitive area and focus it back onto the photosensitive area. A representative example is the adoption of a microlens array to improve photosensitivity by concentrating light traveling outside the photodiode onto the photodiode.

[0005] Such microlens arrays have been proposed in various ways, including in domestic patent registration No. 10-1826962.

[0006] Typically, a microlens array is formed on top of an image sensor, and an objective lens is formed on top of the microlens array to focus light with the microlenses.

[0007] By adopting a microlens array on the upper part of the image sensor in this way, the amount of light that converges on the photodetector can be increased by collecting light that is lost in the process of entering the image sensor.

[0008] However, even when employing a microlens array to focus light onto a photodetector, the relatively small diameter of the lens and aperture limits the amount of light that can be collected. Furthermore, the single-lens configuration limits aberration correction and resolution enhancement.

[0009] The present invention was created to improve the above-mentioned problems, and its purpose is to provide a micro lens array module having a structure capable of increasing the amount of focused light and improving aberration, and a method for manufacturing the same.

[0010] In order to achieve the above object, a micro lens array module according to the present invention comprises: a transparent substrate; first mirrors formed to be spaced apart from each other through a first gap on a first surface of the transparent substrate onto which light is incident, and reflecting light traveling in a direction toward the first surface inside the transparent substrate in a direction toward a second surface of the transparent substrate opposite the first surface; second mirrors arranged inside the transparent substrate to reflect light traveling through a right region from the center of the first gap among light traveling through the first gap of the first surface of the transparent substrate toward the first mirror arranged adjacent to the right; third mirrors arranged inside the transparent substrate to reflect light traveling through a left region from the center of the first gap among light traveling through the first gap of the first surface of the transparent substrate toward the first mirror arranged adjacent to the left; It comprises micro lenses arranged on the second surface of the transparent substrate facing the first mirror to focus incident light.

[0011] In addition, the second mirror and the third mirror are formed in a concave shape that is drawn inward as they progress from both ends to the center.

[0012] Additionally, the first gap is 600 to 1000 μm, and the length of each of the first to third mirrors is applied to 300 to 500 μm.

[0013] Additionally, the thickness between the first surface and the second surface of the transparent substrate is applied as 0.8 to 1.2 mm.

[0014] Additionally, the diameter of the microlens is applied to 300 to 500㎛.

[0015] In addition, in order to achieve the above object, a method for manufacturing a micro lens array module according to the present invention comprises the steps of: a. forming a sacrificial layer with a photoresist on a first surface of a base substrate in the shape of a plate made of a transparent material; b. irradiating light through a mask so that only a first mirror formation area to be formed on the sacrificial layer is irradiated with ultraviolet light and light incidence is blocked in the remaining area, removing the irradiated area, forming a first mirror with a chrome material in the removed first mirror formation area, and removing the remaining sacrificial layer; c. processing an opposing surface opposite to the first surface of the base substrate into a processing surface having a curvature corresponding to the shapes of the second and third mirrors; d. forming a base mirror surface by coating the processing surface of the base substrate with a metal material; e. forming a second and third mirror by removing a portion of the base mirror surface corresponding to a light-transmitting area; f. forming a transparent reinforcing layer on the base substrate so that the second and third mirrors are in an embedded state; g. It includes a step of forming a microlens in a portion corresponding to a light-transmitting area on the surface of the transparent reinforcing layer.

[0016] The micro lens array module and its manufacturing method according to the present invention provide the advantage of being able to increase the amount of focused light, thereby improving the resolution of the image while also improving aberration.

[0017] Fig. 1 is a cross-sectional view showing a micro lens array module according to the present invention.

[0018] Fig. 2 is a process diagram showing the process of manufacturing the micro lens array module of Fig. 1.

[0019] Figure 3 is a layout drawing configured through optical simulation for a micro lens array module according to the present invention.

[0020] Figure 4 is a layout drawing constructed with optical simulation for a microlens comparison module with an omitted mirror.

[0021] Figure 5 is a table showing the data editor configuration for simulation of the micro lens array module of Figure 3.

[0022] Figure 6 is a table showing the data editor configuration for simulation of the comparison module of Figure 4.

[0023] Fig. 7 is a drawing showing the result of a spot diagram analyzed through the micro lens array module of Fig. 3.

[0024] Figure 8 is a drawing showing the results of a spot diagram analyzed through the comparison module of Figure 4.

[0025] Fig. 9 is a diagram showing the results of the point spread function analyzed through the micro lens array module of Fig. 3.

[0026] Figure 10 is a diagram showing the results of the point spread function analyzed through the comparison module of Figure 4.

[0027] Figure 11 is a diagram showing the results of the modulation transfer function (MTF) analyzed through the micro lens array module of Figure 3.

[0028] Figure 12 is a diagram showing the results of the modulation transfer function (MTF) analyzed through the comparison module of Figure 4.

[0029] Figure 13 is a drawing showing an aberration analysis graph (Seidel diagram) analyzed through the micro lens array module of Figure 3.

[0030] Figure 14 is a drawing showing a Seidel diagram of aberration analysis analyzed through the comparison module of Figure 4.

[0031] Hereinafter, a micro lens array module and its manufacturing method according to a preferred embodiment of the present invention will be described in more detail with reference to the attached drawings.

[0032] Fig. 1 is a cross-sectional view showing a micro lens array module according to the present invention.

[0033] Referring to FIG. 1, a micro lens array module (100) according to the present invention includes a transparent substrate (110), a first mirror (120), a second mirror (130), a third mirror (140), and a micro lens (160).

[0034] The transparent substrate (110) is formed in a plate shape using a material with high light transmittance.

[0035] It goes without saying that the transparent substrate (110) can be formed into a structure in which different materials are combined through the manufacturing process.

[0036] The transparent substrate (110) can be formed of various known transparent materials such as glass, quartz, and / or borosilicate glass.

[0037] Additionally, the transparent substrate (110) is cured by ultraviolet rays and can be formed at least in part with the product name Norland Optical Adhesives (NOA) 65, the product name Norland Optical Adhesives (NOA) 68.

[0038] For the convenience of explanation regarding the transparent substrate (110), the surface where light is incident is referred to as the first surface (111), and the surface where the microlens (160) is combined and exposed to the outside on the opposite side of the first surface (111) is referred to as the second surface (112).

[0039] The thickness (t) between the first surface (111) and the second surface (112) of the transparent substrate (110) is applied as 0.8 to 1.2 mm.

[0040] The first mirror (120) is formed to be spaced apart from each other through a first gap (G) on the first surface (111) of the transparent substrate (110) onto which light is incident.

[0041] The first mirror (120) reflects light traveling in the direction of the first surface (111) inside the transparent substrate (110) toward the second surface (112) opposite the first surface (111).

[0042] The first mirror (120) can be formed of a material with high reflectivity, for example, chrome material.

[0043] The length extending along the first surface (111) of the first mirror (120) is applied as 300 to 500 μm.

[0044] Additionally, the first gap (G) can be applied as 600 to 1000 μm.

[0045] The second mirror (130) is arranged in a buried state inside the transparent substrate (110) so that a plurality of them are arranged to reflect the light that travels toward the second surface (112) through the first gap (G) of the first surface (111) of the transparent substrate (110) and travels through the right region from the center (Go) of the first gap (G) toward the first mirror (120) arranged adjacent to the right.

[0046] The second mirror (130) is formed to extend in an arc shape with a concave curvature that is drawn inward as it progresses from both ends to the center. That is, the second mirror (130) is formed so that the central axis of the arc-shaped curvature is inclined to the right, so that light that progresses through the right area from the center (Go) of the first gap (G) is reflected, but the light path is switched to the right, and the reflective surface is formed to have a concave curvature so that the incident light can be focused and reflected.

[0047] The length extending along the first surface (111) of the second mirror (130) is applied as 300 to 500 μm.

[0048] The third mirror (140) is arranged in a buried state inside the transparent substrate (110) so as to reflect the light that travels through the left region from the center (Go) of the first gap (G) of the first surface (111) of the transparent substrate (110) toward the second surface (112) toward the first mirror (120) arranged adjacent to the left, among the light that travels through the left region from the center (Go) of the first gap (G). That is, the third mirror (140) is arranged so that the central axis of the arc-shaped curvature is inclined to the left, so that the light that travels through the left region from the center (Go) of the first gap (G) is reflected, but the optical path is switched to the left, and the reflective surface is formed to have a concave curvature so as to focus and reflect the incident light.

[0049] The third mirror (140) is formed to extend in an arc shape with a concave curvature that becomes inward as it progresses from both ends to the center.

[0050] The length extending along the first surface (111) of the third mirror (140) is applied as 300 to 500 μm.

[0051] The second mirror (130) and the third mirror (130) are arranged adjacent to each other and are positioned opposite to the gap (G) to reflect light incident through the gap (G) toward the first mirror (120) arranged on the right and left, respectively.

[0052] A micro lens (160) is placed on the second surface (112) of the transparent substrate (110) facing the first mirror (120) to focus incident light.

[0053] The micro lens (160) is a convex collimating lens applied to focus light reflected from the first mirror (120) and traveling toward the second surface (112).

[0054] The diameter of the micro lens (160) is applied to be 300 to 500㎛.

[0055] According to this structure, light that travels through the first gap (G) on the first surface (111) of the transparent substrate (110) in a direction from the first surface (111) of the transparent substrate (110) toward the second surface (112) travels into the interior of the transparent substrate (110) and is reflected by the second and third mirrors (130) (140) and travels to the first mirror (120), and the light reflected by the first mirror (120) is focused and emitted through the microlens (160) at the opposite position.

[0056] Hereinafter, the manufacturing process of such a microlens array module (100) will be described with reference to Fig. 2. Elements having the same function as those in the previously illustrated drawing are indicated with the same reference numerals.

[0057] First, a sacrificial layer (210) is formed using a photoresist on the first surface (111) of a base substrate (110a) in the shape of a plate made of a transparent material. Here, the base substrate (110a) is an element forming part of the transparent substrate (110) and can be formed of various known materials such as quartz and / or borosilicate glass as described above.

[0058] Next, ultraviolet light is irradiated through a mask (220) formed so that only the first mirror formation area (211) to be formed on the sacrificial layer (210) is irradiated with ultraviolet light and light incidence is blocked in the remaining areas, and after the first mirror formation area (211) irradiated with ultraviolet light is removed, a first mirror (120) is formed with a chrome material in the removed first mirror formation area (211), and the remaining sacrificial layer (210) is removed.

[0059] The thickness of the first mirror (120) is appropriately applied to be 100 nm or more.

[0060] Afterwards, the base substrate (110a) is turned over and the opposing surface (113) opposite the first surface (111) of the base substrate (110a) is processed using a processing machine (250) to form a processing surface (115) having a curvature corresponding to the second and third mirror shapes.

[0061] Then, the processing surface (115) formed on the base substrate (110a) is coated with a metal material having a high reflectivity, for example, chrome material, to form a base mirror surface (135). The thickness of the base mirror surface (135) is appropriately applied to be 100 nm or more.

[0062] In the next step, the portion corresponding to the light-transmitting area of ​​the base mirror (135) is removed using a processing machine (250) to form the second and third mirrors (130) (140).

[0063] Finally, a transparent reinforcing layer (110b) is formed on the base substrate (110a) so that the second and third mirrors (130)(140) are embedded.

[0064] The transparent reinforcing layer (110b) may be formed of the same material as the base substrate (110a). As an example, the transparent reinforcing layer (110b) may be formed by applying the previously described Norland Optical Adhesives (NOA) 65 or Norland Optical Adhesives (NOA) 68 and curing it with ultraviolet rays.

[0065] After the transparent reinforcing layer (110b) is formed, it can be processed flat through polishing.

[0066] Finally, a microlens (160) is formed on a portion of the surface of the transparent reinforcing layer (110b) corresponding to the light-transmitting area.

[0067] The microlens (160) can be formed in various ways, such as by molding the transparent reinforcing layer (110b) and then manufacturing it through a heat treatment (thermal reflow) process.

[0068] According to the structure of this microlens array module (100), the imaging area can be controlled by controlling the optical path conversion structure of the second and third mirrors (130) (140) provided inside the transparent substrate (110) and the first mirror (120) formed on the first surface (111).

[0069] Meanwhile, in order to determine the performance of the microlens array module (100) according to the present invention, an evaluation was performed on a comparative module to which the first to third mirrors (120 to 140) were not applied in the microlens array module (100) according to the present invention, and the results of the evaluation are described below.

[0070] First, the layout of FIG. 3 was applied to the microlens array module according to the present invention through Zemax, an optical design program, and the layout of FIG. 4 was applied to a comparative module to which only microlenses were applied without a mirror optical system.

[0071] In addition, the data editor configuration for simulation of the micro lens array module of FIG. 3 was applied as illustrated in FIG. 5, and the data editor configuration for simulation of the comparison module of FIG. 4 was applied as illustrated in FIG. 6. Here, the specifications of the micro lenses were applied equally to both the module of the present invention and the comparison module.

[0072] As can be confirmed by comparing Figs. 7 and 8 with the results of this simulation, the beam diameter of the comparative module constructed only with micro lenses without a mirror optical system was 42.82 um (RMS standard) (see Fig. 8), whereas the beam diameter of the module of the present invention was 3.002 um (RMS standard) (see Fig. 7).

[0073] In addition, as a result of analyzing the shape of the spot through the point spread function, it can be confirmed that the spot of the module according to the present invention (see Fig. 9) has a beam focused more clearly than the comparative module (see Fig. 10).

[0074] In addition, in the MTF results indicating the image resolution, the MTF of a single micro lens was 0.116 in the Modulus of the OTF at 40 lp / mm in Fig. 12, but it can be confirmed that the resolution of the module of the present invention was greatly improved to 0.7857 in Fig. 11.

[0075] In addition, the results of the aberration analysis graph (Seidel diagram) for aberration analysis are shown in Figs. 13 and 14, and both the module of the present invention and the comparative module showed high spherical aberration. However, the grid line scale of the comparative module was 1 mm, but the grid line scale of the module according to the present invention was 0.001 mm, showing improved aberration.

[0076] These micro lens array modules can be installed not only in fields requiring small cameras such as endoscope cameras, surveillance and reconnaissance robot cameras, but also in mobile digital cameras.

[0077] According to the micro lens array module of the present invention described above and the manufacturing method thereof, not only does it use a micro lens with a low focal length, but it also has the advantage of being able to manufacture the entire lens with an ultra-thin thickness by utilizing an ultra-precision manufacturing process method for the mirror structure. In addition, the micro lens array module of the present invention has the effect of improving image resolution and correcting aberrations by efficiently focusing a beam even with a structure with a low thickness.

Claims

1. Transparent substrate; First mirrors formed to be spaced apart from each other through a first gap on the first surface of the transparent substrate onto which light is incident, and reflecting light traveling in a direction toward the first surface within the transparent substrate in a direction toward the second surface of the transparent substrate opposite the first surface; Second mirrors arranged inside the transparent substrate to reflect light that passes through the first gap of the first surface of the transparent substrate and passes through a region to the right of the center of the first gap toward the first mirror arranged adjacent to the right; Third mirrors arranged inside the transparent substrate to reflect light that passes through the first gap of the first surface of the transparent substrate and passes through a left area from the center of the first gap toward the first mirror arranged adjacent to the left; A micro lens array module characterized by comprising micro lenses arranged on the second surface of the transparent substrate facing the first mirror to focus incident light.

2. A micro lens array module characterized in that, in the first paragraph, the second mirror and the third mirror are formed in a concave shape that is drawn inward from both ends toward the center.

3. A micro lens array module, characterized in that in the first paragraph, the first gap is 600 to 1000 μm, and the length of each of the first to third mirrors is 300 to 500 μm.

4. A micro lens array module according to claim 3, characterized in that the thickness between the first surface and the second surface of the transparent substrate is 0.8 to 1.2 mm.

5. A micro lens array module according to claim 3, characterized in that the diameter of the micro lens is 300 to 500 μm.

6. A step of forming a sacrificial layer using photoresist on the first surface of a base substrate in the shape of a plate made of a transparent material; B. A step of performing light irradiation through a mask so that only the first mirror formation area to be formed on the sacrificial layer is irradiated with ultraviolet light and the remaining areas are blocked from light incidence, removing the area irradiated with light and forming a first mirror with a chrome material in the removed first mirror formation area, and removing the remaining sacrificial layer; A step of processing the first surface of the base substrate into a processing surface having a curvature corresponding to the second and third mirror shapes on the opposite surface; A step of forming a base mirror surface by coating the processed surface of the base substrate with a metal material; Step of forming second and third mirrors by removing a portion corresponding to the light transmitting area among the base mirror surfaces; A step of forming a transparent reinforcing layer on the base substrate so that the second and third mirrors are embedded; A method for manufacturing a micro lens array module, characterized by comprising the step of forming a micro lens on a portion corresponding to a light transmission area of ​​the surface of the transparent reinforcing layer.

7. A method for manufacturing a micro lens array module, characterized in that in the 6th paragraph, the first gap between the first mirrors is 600 to 1000 μm, and the length of each of the first to third mirrors is 300 to 500 μm.

8. A method for manufacturing a micro lens array module, characterized in that in the 7th paragraph, the total thickness of the base substrate and the transparent reinforcing layer is 0.8 to 1.2 mm.

9. A method for manufacturing a micro lens array module, characterized in that in the 7th paragraph, the diameter of the micro lens is 300 to 500㎛.

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