KR102576800B1 - Microlens array with selective transmittance control coating - Google Patents

Abstract

The present invention relates to a micro lens array in which a plurality of micro lenses are arranged to be spaced apart from each other on a substrate, wherein at least one differential transmission area is sequentially set along the direction of increasing distance from the central area set for the micro lenses. The transmittance of the transmission adjustment coating layer formed on the surface of the micro lens disposed in the central region is formed to have a lower transmittance than the transmittance of the transmission adjustment coating layer formed on the surface of the micro lens located in the differential transmission region. This selective transmittance-adjustable microlens array and its manufacturing method provide the advantage of alleviating regional imbalances in light collected by an image sensor.

Description

Selective transmittance controllable micro lens array and manufacturing method thereof {Microlens array with selective transmittance control coating}

The present invention relates to a selective transmittance-adjustable micro-lens array and a method of manufacturing the same. More specifically, it relates to a selective transmittance-adjustable micro-lens array and a method of manufacturing the same, which can alleviate regional imbalances in light collected by an image sensor.

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.

These image sensors use light-sensing elements such as photodiodes to detect light, and the resolution of the image is determined by the number of light-sensing elements. However, as various imaging devices have recently developed toward miniaturization and high resolution, image sensors used in imaging devices are also changing to miniaturization, higher resolution, and higher integration. Due to the miniaturization, high pixel resolution, and high integration of image sensors, the number of pixels per unit area of the image sensor is greatly increasing, and the size of the unit pixel is correspondingly reduced.

As the unit pixel size is reduced, the area of the photo-sensing element that receives light inside the image sensor is also bound to be reduced, and the reduction of the area of the photo-sensing element ultimately leads to a decrease in light sensitivity. Accordingly, recently, a lot of research has been done on light-concentrating technology that converts the path of light incident outside the light-sensing area and focuses it into the light-sensing area. Typically, light traveling outside the photodiode is condensed by the photodiode. Microlens arrays are being adopted to improve light sensitivity.

Such microlens arrays have been proposed in various ways, including in Korea Registered Patent No. 10-1826962.

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 using the microlenses.

In this way, by adopting a microlens array on the top of the image sensor, it is possible to increase the amount of light converged on the light sensing element by concentrating light that is lost in the process of entering the image sensor.

However, even if a microlens array is used to focus light on the light sensing element, there is a large difference in the amount of light concentrated on the light sensing element in the center pixel area and the edge pixel area of the image sensor.

In other words, light incident on the central pixel area of the image sensor is accurately focused onto the upper surface of the photodiode in the central pixel area through the microlens in the central pixel area. In contrast, light incident on the edge pixel area of the image sensor is incident at a predetermined inclination, and is refracted at a certain angle through a microlens in the edge pixel area and focused on the edge pixel area. However, since the light incident on the edge pixel area of the image sensor is incident at a predetermined angle, it is not exactly incident on the center of the photodiode in the edge pixel area, but rather is focused on the surrounding area of the photodiode or the front of the photodiode. Because the light is concentrated to the outside rather than to the outside, the photo-sensitivity of the edge pixel area is lowered compared to the central pixel area, causing a problem of lower peripheral light ratio.

As an alternative to solving this problem of lowering the peripheral light ratio, a configuration has been proposed in which the optical axis of the microlens in the peripheral pixel area is crossed with the optical axis of the corresponding photodiode. In other words, the microlens in the central pixel area of the image sensor is formed so that its center is located on the same optical axis as the photodiode in the corresponding central pixel area, as before, while the microlens in the edge pixel area of the image sensor is formed as before. Otherwise, compared to the photodiode in the corresponding edge pixel area, it is not located on the same optical axis. That is, the microlens in the edge pixel area moves toward the center of the image sensor by a certain distance compared to the photodiode in the edge pixel area. However, some of the light incident on the peripheral pixel area of the image sensor having this configuration is still not focused on the photodiode. In addition, due to the difference in slope of light incident on the central pixel area and the surrounding pixel area of the image sensor, microlenses with the same characteristics cannot sufficiently converge light into the surrounding pixel area. Therefore, the microlenses formed in the central pixel area and the edge pixel area must have different characteristics, which makes the process complicated and virtually impossible to form a general microlens.

Therefore, there is a need for a micro lens array that can alleviate regional imbalances in light collected by an image sensor.

The present invention was created to solve the above requirements, and its purpose is to provide a selective transmittance-adjustable microlens array that can alleviate regional imbalances in light collected by an image sensor and a method of manufacturing the same.

In order to achieve the above object, the selective transmittance-adjustable microlens array according to the present invention is a microlens array in which a plurality of microlenses are arranged to be spaced apart from each other on a substrate, from the central area set for the microlenses to the central area. At least one differential transmission area is sequentially set along the direction of increasing distance, and the transmittance of the transmission adjustment coating layer formed on the surface of the micro lens disposed in the central area is the transmission rate formed on the surface of the micro lens located within the differential transmission area. It is formed to have a lower transmittance than the transmittance of the adjustment coating layer.

In addition, the diameter of the microlens is 150 to 350㎛.

According to one aspect of the present invention, the microlenses are arranged at equal intervals on a matrix along a first direction and a second direction orthogonal to the first direction, and the differential transmission areas are based on the center of the central area. It is applied sequentially concentrically along the direction of increasing distance, and the transmittance between the differential transmission areas is set to gradually increase along the direction of increasing distance from the central area.

According to another aspect of the present invention, the microlenses are arranged at equal intervals on a matrix along a first direction and a second direction orthogonal to the first direction, and the central area is a central microlens located at the center. and four primary orthogonally arranged micro lenses arranged adjacently in the first direction and the second direction, and a first differential transmission area applied adjacent to the central area is the first orthogonally arranged micro Four secondary orthogonal microlenses adjacent to the lens and arranged along the first and second directions, and four secondary orthogonal microlenses arranged in a diagonal direction of 45 degrees around the central microlens, are interconnected with each other. It is set to include four diagonally arranged microlenses arranged on a connecting line.

In addition, the transmission adjustment coating layer formed on the surface of the micro lens disposed in the central region and the transmission adjustment coating layer formed on the surface of the micro lens located in the differential transmission region have different thicknesses and are preferably formed of ZnO.

In addition, in order to achieve the above object, a method of manufacturing a selective transmittance-adjustable microlens array according to the present invention is a. Microlenses within the differential transmission area where a transmission adjustment coating layer must be formed with a minimum thickness for a plurality of differential transmission areas to which different transmittances are applied sequentially along the direction of increasing distance from the central area set for the micro lenses. forming a transmission adjustment coating layer to a minimum thickness through a first mask from the microlens in the central region; me. Microlenses in the central area from microlenses in the differential transmission area where a transmission adjustment coating layer is to be formed with a first thickness thicker than the minimum thickness and corresponding to the next transmittance set lower than the transmittance corresponding to the transmission adjustment coating layer of the minimum thickness. From the process of forming a transmission adjustment coating layer through a second mask having a smaller transmission area than the first mask, a transmission adjustment coating layer is applied to the microlens in the central area with a final thickness corresponding to the transmittance of the microlens corresponding to the central area. It includes the step of sequentially applying and coating a central mask having a central area transmission area to form a coating process.

The selective transmittance-adjustable microlens array and its manufacturing method according to the present invention provide the advantage of alleviating regional imbalance of light collected in an image sensor.

1 is a perspective view showing a selective transmittance-adjustable microlens array according to a first embodiment of the present invention;
Figure 2 is a cross-sectional view of the micro lens array of Figure 1;
Figure 3 is a plan view for explaining the differential transmittance distribution area of the micro lens array of Figure 1;
Figure 4 is a plan view for explaining the differential transmittance distribution area of the micro lens array according to the second embodiment of the present invention;
Figure 5 is a plan view for explaining the differential transmittance distribution area of the micro lens array according to the third embodiment of the present invention;
Figure 6 is a process diagram for explaining the manufacturing process of the micro lens array according to the present invention;
Figure 7 is a photograph showing a comparison of image processing results between the transmittance correction structure of the microlens array according to the present invention and the conventional structure.

Hereinafter, a selective transmittance-adjustable micro-lens array and a manufacturing method thereof according to a preferred embodiment of the present invention will be described in more detail with reference to the accompanying drawings.

Figure 1 is a perspective view showing a selective transmittance-adjustable micro lens array according to the present invention, and Figure 2 is a cross-sectional view of the micro lens array of Figure 1.

Referring to Figures 1 and 2, the micro lens array 10 according to the present invention has a plurality of micro lenses 30 arranged on a plate-shaped substrate 20 to be spaced apart from each other.

The substrate 20 is a support that supports and arranges the microlenses 30 and may be formed of the same material as the microlenses 30.

Microlenses 30 are arranged at equal intervals on a matrix along a first direction and a second direction orthogonal to the first direction on the substrate 20. Here, the first direction is a horizontal direction in the drawing, and the second direction is a vertical direction in the drawing.

Of course, the microlenses 30 may be arranged on the substrate 20 in an arrangement pattern different from the example shown.

The diameter of the microlens 30 is 150 to 350㎛.

These microlenses 30 have at least one differential transmission area set sequentially along the direction of increasing distance from the central area, which is set to alleviate regional imbalance of light collected by the image sensor (not shown). .

The differential transmission areas according to one aspect of the present invention are applied sequentially along the direction of increasing distance concentrically based on the center of the central area, and the transmittance between the differential transmission areas is increased along the direction of increasing distance from the central area. It is set to gradually increase, and an example is described with reference to FIG. 3.

In Figure 3, the area indicated by reference numeral 50a is the central area, and the area with the first diameter in the direction in which the outer diameter is concentrically expanded from the central area 50a around the central area 50a is the first differential transmission area ( 50b), and the area having a second diameter larger than the first diameter in the direction in which the outer diameter expands from the first differential transmission area 50b around the central area 50a is the second differential transmission area 50c, and the central area 50c is An area having a third diameter larger than the second diameter in a direction in which the outer diameter is expanded from the second differential transmission area 50c around the area 50a is the third differential transmission area 50d. The area having a fourth diameter larger than the third diameter in the direction in which the outer diameter is expanded from the third differential transmission area 50d centered on the central area 50a is an uncoated area 50e in which a transmission adjustment coating layer to be described later is not formed. It is set to .

In this case, the transmittance of the transmission adjustment coating layer 40a formed on the surface of the micro lens 30 disposed in the central region 50a is that of the micro lens 30 located within the first to third differential transmission regions 50b to 50d. It is formed to have a lower transmittance than the transmittance of the transmission adjustment coating layers 40b to 40d formed on the surface, and as an example, it is formed as a transmission adjustment coating layer 40a having a transmittance of 95%.

In addition, the transmittance of the transmission adjustment coating layer 40c formed on the surface of the micro lens 30 located in the second differential transmission area 50c is the transmittance formed on the surface of the micro lens 30 located in the first differential transmission area 50b. It is formed to have a higher transmittance than the transmittance of the adjustment coating layer 40b, and as an example, it is formed to have a transmittance of 96%.

Likewise, the transmittance of the transmission adjustment coating layer 40d formed on the surface of the micro lens 30 located in the third differential transmission area 50d is the transmittance formed on the surface of the micro lens 30 located in the second differential transmission area 50c. It is formed to have a higher transmittance than the transmittance of the adjustment coating layer 40c, and as an example, it is formed to have a transmittance of 97%.

A transmission adjustment coating layer is not formed on the micro lens 30 located in the uncoated area 50e.

Here, a transmission adjustment coating layer (40a) formed on the surface of the micro lens 30 disposed in the central region (50a) and a transmission adjustment coating layer (40a) formed on the surface of the micro lens (30) located in the first to third differential transmission regions (50b to 50d). It is preferable that all of the transmission adjustment coating layers 40b to 40d are made of the same ZnO material and have different thicknesses to adjust the transmittance.

In this case, the transmission adjustment coating layers 40a to 40d may be formed by depositing ZnO, which is applied as a coating material, at different thicknesses through E-beam evaporation.

Meanwhile, ZnO material shows transmittance as shown in Table 1 below depending on the thickness, and the desired transmittance can be adjusted by adjusting the thickness.

ZnO thickness (nm) Average transmittance (%) 14.2 95.0 42.7 90.4 51.4 88.7

According to this structure, the transmittance of the microlens 30 disposed in the central area 50a is the lowest, and the transmittance gradually increases toward the edge, thereby relieving regional imbalance of light collected by the image sensor (not shown). You can.

Meanwhile, in the microlens array, a differential transmission area in which the transmittance is set to increase sequentially from the central area to the edge may be applied differently from the example shown, and the example will be described with reference to FIG. 4.

Referring to FIG. 4, as before, microlenses 30 are arranged at equal intervals on a matrix along a first direction and a second direction orthogonal to the first direction on the substrate 20, and a central region ( 150a) is set to include four primary orthogonal microlenses 30a1 to 30a4 arranged adjacently along the first and second directions with the central microlens 30a located at the center.

In addition, the first differential transmission area 150b applied adjacent to the central area 150a is adjacent to the first orthogonal microlenses 30a1 to 30a4 and includes four secondary transmissive areas arranged along the first and second directions. Four diagonal arrays are arranged in a 45-degree diagonal direction around the orthogonal microlenses (30b1 to 30b4) and the central microlens (30a), and are arranged on a line connecting the secondary orthogonal microlenses (30b1 to 30b4). It is set to include microlenses 30b5 to 30b8. The remaining second differential transmission area (150c), third differential transmission area (150d), fourth differential transmission area (150e), and fifth differential transmission area (150f) are sequentially set in the direction in which the radius extends from the central area (150a). ) is set to the same expansion pattern.

In this case, as an example, the transmittance of the central region 150a is 94%, the transmittance of the first differentially transparent region 150b is 95%, the transmittance of the second differentially transparent region 150c is 96%, and the transmittance of the third differentially transparent region 150c is 96%. The transmittance of the (150d) is 97%, the transmittance of the fourth differential transmission area (150e) is 98%, and the transmittance of the fifth differential transmission area (150f) is 99%. can be formed.

Meanwhile, as shown in FIG. 5, the microlens array structure can be arranged so that the microlenses are arranged in positions that are offset from each other in a zigzag shape along the longitudinal direction. In this case, the portion indicated by reference numeral 250a is referred to as the central area, and the portion indicated by reference numeral 250a is referred to as the central region. The part marked 250b is the first differential transmission area, the part marked 250c is the second differential transmission area, the part marked 250d is the third differential transmission area, and the part marked 250e is the fourth differential transmission area. It can be built to set up. In addition, the transmittance of the central area 250a is 87%, the transmittance of the first differentially transparent area 250b is 90%, the transmittance of the second differentially transparent area 250c is 93%, and the transmittance of the third differentially transparent area 250d is 93%. A transmission adjustment coating layer may be formed on the corresponding microlens so that the transmittance is 96% and the transmittance of the fourth differential transmission area 250e is 99%.

In this way, the order and differential transmittance values of the differential transmission areas sequentially divided toward the center area and the edge can be applied appropriately according to the application environment.

Hereinafter, the manufacturing method of such a micro lens array will be described with reference to FIG. 6. For reference, in order to avoid complexity of explanation, reference numerals indicate the case of manufacturing a microlens array having a coating layer of the structure shown in FIG. 2.

First, a transmission adjustment coating layer 40d with a minimum thickness is applied to a plurality of differential transmission areas to which different transmittances are sequentially applied along the direction of increasing distance from the central area from the set central area described above for the micro lenses 30. A transmission adjustment coating layer (40d) with a minimum thickness through the first mask (110) having a first opening (111a) corresponding to the microlens (30) in the differential transmission area to be formed to the microlens (30) in the central area. forms. In the illustrated example, the microlens 30 in the central region is coated with the thickness of the transmission adjustment coating layer 40d applied to the third differential transmission region through the first mask 110.

Next is the microlens in the differential transmission area where the transmission adjustment coating layer 40c is to be formed with a first thickness thicker than the minimum thickness, corresponding to the next transmittance set lower than the transmittance corresponding to the transmission adjustment coating layer 40d of the minimum thickness ( 30) to the microlens 30 in the central area, forming a transmission adjustment coating layer 40c through the second mask 112 having a second opening 112a with a smaller transmission area than the first mask 111. do. The area where coating is performed by the second mask 112 is coated secondarily on the coating previously formed by the first mask 111, so that the overall thickness becomes the first thickness.

This process corresponds to the next transmittance and creates a second mask (112) corresponding to the area from the microlens in the differential transmission area to the microlens in the central area where the transmission adjustment coating layer (40b) is to be formed with a second thickness thicker than the first thickness. ) A transmission adjustment coating layer 40b is formed through the third mask 112 having a third opening 113a having a smaller transmission area than ). Finally, a center having an opening 114a corresponding to the central region transmission area for forming a transmission adjustment coating layer on the microlens 30 in the central region with a final thickness corresponding to the transmittance of the microlens 30 corresponding to the central region. Coating is performed by sequentially applying the mask 114 to the coating process. Accordingly, the final thickness of the microlens 30 in the central area is determined through a fourth overlapping coating process using the first to third masks 111 to 113 and the central mask 114.

In this method, the edge area has the smallest number of coating layers and the central area has the largest number of coating layers, so that the transmittance can be adjusted to the desired differential conditions.

Meanwhile, a light blocking layer 21 using a black polymer capable of ultraviolet (UV) patterning is applied to the area between each microlens 30 on the upper surface of the substrate 20 to reduce optical crosstalk. Here, as an example, the black polymer can be applied as a material with the product name Black SU-8 and part number GMC 1040 manufactured by Gersteltec, Switzerland.

The selective transmittance-adjustable microlens array described above can acquire images with different transmittances from each microlens of the microlens array, and due to this effect, the existing CRA (Chief ray angle) occurs in each microlens. The brightness/saturation difference can be corrected as shown in FIG. 7.

Additionally, by correcting the brightness/saturation differences occurring in each microlens, the effect of super-resolution imaging, which improves resolution by combining multiple microlens array images, can be maximized. In addition, the vignetting effect can be controlled by the light blocking layer 21 formed of a patterned black polymer to reduce optical cross-talk between microlenses.

20: substrate 30: micro lens

Claims (7)

In a micro lens array in which a plurality of micro lenses are arranged to be spaced apart from each other on a substrate,
At least one differential transmission area is sequentially set from the central area set for the micro lenses in a direction increasing the distance from the central area, and the transmittance of the transmission adjustment coating layer formed on the surface of the micro lens disposed in the central area is is formed to have a lower transmittance than the transmittance of the transmission adjustment coating layer formed on the surface of the micro lens located within the differential transmission area,
The diameter of the microlens is 150 to 350㎛,
The microlenses are arranged at equal intervals on a matrix along a first direction and a second direction orthogonal to the first direction, and the central area is located in the first direction and the center around the central microlens located at the center. It includes four primary orthogonally arranged micro lenses arranged adjacently along a second direction, and a first differential transmission area applied adjacent to the central area is adjacent to the first orthogonal arranged micro lenses and is aligned with the first direction. Four secondary orthogonal microlenses arranged along the second direction and four diagonal lines arranged in a diagonal direction of 45 degrees around the central microlens and arranged on a line connecting the secondary orthogonal microlenses to each other. A selective transmittance tunable microlens array configured to include batched microlenses. delete delete delete The method of claim 1, wherein the transmission adjustment coating layer formed on the surface of the micro lens disposed in the central region and the transmission adjustment coating layer formed on the surface of the micro lens located in the differential transmission region have different thicknesses and are formed of ZnO. Selective transmittance-tunable microlens array. delete delete

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