KR102076803B1 - Optical filter and camera module for comprising the same - Google Patents

Abstract

The optical filter according to an embodiment of the present invention comprises a substrate, a buffer layer formed on the substrate, and a coating layer formed on the buffer layer, the first thin film layer and the second thin film layer having different refractive indices alternately formed at least two or more times. It includes, and is set so that the transmittance for each wavelength region is different within the range of 415nm to 495nm wavelength.

Description

Optical filter and a camera module including the same {OPTICAL FILTER AND CAMERA MODULE FOR COMPRISING THE SAME}

The present invention relates to a camera module, and more particularly, to an optical filter and a camera module including the same.

With the development of smart phones and cameras embedded therein, demands for slimming, low power consumption, high resolution and light weight are increasing. Complementary Metal-Oxide Semiconductor (CMOS) sensors, which are typically used in camera modules, have high sensitivity to red, which makes the image red. Accordingly, it is necessary to block the near infrared rays from being sensed by the sensor using the IR filter.

An example of an IR filter is a reflective filter in which high and low refractive materials are stacked on a glass substrate. The reflective filter reflects and shields near infrared rays entering the camera module.

Another example of an IR filter is an absorption filter, which is a glass substrate to which an absorber that selectively absorbs light of 700 nm or more is added. The absorption filter absorbs near infrared rays entering the camera module and may be called a blue filter or blue glass.

Such an IR filter has a problem of color bleeding of blue light. This is because the amount of blue light passing through the filter is large and a shift of the blue light occurs depending on the incident angle.

Particularly, when the DOE pattern is formed on the surface of the lens according to the slimming trend of the camera module, the transmittance of blue light is further increased, and the difference in blue light transmittance between the central part and the peripheral part is increased.

An object of the present invention is to provide an optical filter and a camera module including the same.

An optical filter according to an embodiment of the present invention includes a substrate, a buffer layer formed on the substrate, a coating layer formed on the buffer layer, the first thin film layer having a different refractive index, and the second thin film layer alternately formed at least two or more times. In addition, the transmittance for each wavelength region is set within the range of 415 nm to 495 nm.

The substrate may include an absorber set to vary transmittance for each wavelength region within a range of 415 nm to 495 nm.

The substrate may have a transmittance of 10% to 40% within a range of 415 nm to 495 nm in wavelength.

The transmittance for the first wavelength region having a wavelength of 415 nm to 450 nm may be 10% to 25%, and the transmittance for the second wavelength region having a wavelength of 450 nm to 495 nm may be 25% to 40%.

The substrate may further include an absorber for absorbing near infrared rays.

The coating layer may be thicker from the center toward the periphery.

At least one of the at least one first thin film layer and the at least one second thin film layer may be formed to a thickness of 0.15 to 0.35 times of 415 nm to 495 nm.

At least one of the at least one first thin film layer and the at least one second thin film layer is formed at a thickness of 0.15 to 0.35 times the thickness of 415 nm to 450 nm, and is located at the edge of the first region, and is 0.15 of 450 nm to 495 nm. It may include a second region formed to a thickness of 0.35 times.

The first thin film layer may include TiO ₂ , and the second thin film layer may include SiO ₂ .

Camera module according to an embodiment of the present invention is mounted on a printed circuit board, the printed circuit board, an image sensor connected to the printed circuit board by a wire, is formed on the image sensor, the wavelength is 415nm to 495nm An optical filter is set so that the transmittance for each wavelength region is different within a phosphorus range, a lens assembly formed on the optical filter, and a lens holder in which the optical filter and the lens assembly are built and supported.

The lens assembly may include a lens having a diffractive optical element (DOE) pattern formed thereon.

According to the embodiment of the present invention, an optical filter having a lower transmittance and a wavelength shift of blue light can be obtained. Accordingly, it is possible to reduce the color bleeding problem of the blue light, and to reduce the color bleeding difference between the central portion and the peripheral portion. In particular, it can be applied to a camera module including a lens having a DOE pattern, it is also possible to implement a slim camera module.

1 illustrates a cross-sectional view of a camera module.
2 is an image obtained from a camera module including a DOE lens and a 415 nm CUT IR filter.
3 is an enlarged view of portion A of FIG. 2, and FIG. 4 is an enlarged view of portion B of FIG. 2.
5 is a graph illustrating a wavelength shift phenomenon according to an incident angle, and FIG. 6 is an enlarged graph of the blue light region of FIG. 5.
7 is a cross-sectional view of an optical filter according to an embodiment of the present invention.
8 is a graph comparing refractive indices of wavelengths of TiO ₂ and SiO ₂ .

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated and described in the drawings. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers, such as second and first, may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the second component may be referred to as the first component, and similarly, the first component may also be referred to as the second component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is said to be "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that another component may be present in the middle. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art, and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

Hereinafter, exemplary embodiments will be described in detail with reference to the accompanying drawings, and the same or corresponding components will be given the same reference numerals regardless of the reference numerals, and redundant description thereof will be omitted.

In the present specification, an example of an optical filter will be described based on an IR filter, but this is only an example, and the technical spirit of the present invention is not limited thereto. Embodiments of the present invention can be applied to various optical filters as well as IR filters.

1 illustrates a cross-sectional view of a camera module.

Referring to FIG. 1, the camera module 100 includes a printed circuit board 110, an image sensor 120, an infrared (IR) filter 130, a lens assembly 140, and a lens holder 150.

The image sensor 120 is mounted on the printed circuit board 110, and the image sensor 120 is connected to the printed circuit board 110 by wires 112. The image sensor 120 may be, for example, a charge-coupled device (CCD) or a CMOS sensor.

An IR filter 130 is formed on the image sensor 120. The IR filter 130 selectively blocks near infrared light, for example, light having a wavelength between 700 nm and 1100 nm, from light incident in the camera module 100.

The lens assembly 140 is formed on the IR filter 130. The lens assembly 140 may include a lens in which a diffuse optical element (DOE) pattern is formed.

In addition, the IR filter 130 and the lens assembly 140 are embedded in the lens holder 150 and supported.

In this case, the color blurring problem of blue light may occur in the image obtained from the camera module 100. This is because the amount of blue light transmitted through the IR filter 130 is large, and a wavelength shift of the blue light occurs according to the incident angle. In particular, when the lens includes a DOE pattern, the color bleeding of the blue light may become more severe.

For example, in the case of an image obtained from a camera module including a general lens, the blue light transmittance of the central part and the peripheral part is about 5%. However, for images obtained from a camera module comprising a DOE lens and a 415 nm CUT IR filter that blocks light having a wavelength of 415 nm or less, the blue light transmittance at the center is about 13% and the blue light transmittance at the periphery is about 37%.

2 is an enlarged view of portion A of FIG. 2, and FIG. 4 is an enlarged view of portion B of FIG. 2. As described above, when the lens having the DOE pattern is formed to reduce the camera module and improve chromatic aberration, the color blur of the blue light is severe, and the peripheral portion at the center of the image (part A of FIG. 2, for example, 0.0F to 0.5F) is used. (B part of FIG. 2, for example, 0.5F to 1.0F), the color bleeding of blue light becomes more severe. This is because the noise of the red light and the blue light is similar at the center of the small incident angle, but the noise of the blue light is significantly increased at the peripheral portion having the large incident angle, resulting in a wavelength shift.

5 is a graph illustrating a wavelength shift phenomenon according to an incident angle, and FIG. 6 is an enlarged graph of the blue light region of FIG. 5. 5 to 6, when the wavelength shift of the blue light occurs according to the incident angle, the degree of color blur between the center and the peripheral portion of the image is changed, and the quality of the image is degraded.

According to an embodiment of the present invention, an optical filter is set to change transmittance for each wavelength region in a blue light range.

In the present specification, the transmittance (%) means the rate at which light transmitted through the optical filter. In addition, blue light means light having a wavelength range of 415 nm to 495 nm, preferably 430 nm to 460 nm.

7 is a cross-sectional view of an optical filter according to an embodiment of the present invention.

Referring to FIG. 7, the optical filter 700 includes a substrate 710, a buffer layer 720, and a coating layer 730. The thickness of the optical filter 700 may be 0.3 mm or less. Here, the optical filter 700 may be, for example, an IR filter that blocks near infrared rays from light incident on the camera module.

The substrate 710 may be a resin, a film, or glass having a visible light transmittance of 90% or more and a glass transition temperature of 100 ° C. or more.

The buffer layer 720 is formed on the substrate 710, and the coating layer 730 is formed on the buffer layer 720. In the coating layer 730, the first thin film layer 731 and the second thin film layer 732 having different refractive indices may be alternately formed at least two times. The first thin film layer 731 may include TiO ₂ , and the second thin film layer 732 may include SiO ₂ .

When the reference wavelength to be blocked is Xnm, by setting the thickness of at least one of the first thin film layer and the second thin film layer to 0.15Xnm to 0.35Xnm, preferably 0.2Xnm to 0.3Xnm, the reflectance with respect to the reference wavelength can be optimized. have. For example, when the reference wavelength is 820 nm, when the thickness of at least one of the first thin film layer and the second thin film layer is set to 123 nm to 328 nm, preferably 164 nm to 246 nm, the reflectance with respect to near infrared rays can be increased.

The thickness ratio of the first thin film layer and the second thin film layer may be based on the refractive index (n) of the material included in each thin film layer. Referring to FIG. 8, which is a graph comparing the refractive indexes of TiO ₂ and SiO ₂ by wavelength, the ratio of the refractive indexes of TiO ₂ and SiO ₂ at 820 nm is about 2.8 / 1.55 (= 1.81). Accordingly, the thickness of the second thin film layer can be set to be 1.81 times the thickness of the first thin film layer.

According to an embodiment of the present invention, in order to set the transmittance for each wavelength region in the blue light range, the substrate 710 or the coating layer 730 may be set to change the transmittance for each wavelength region within a range of 415 nm to 495 nm. It may include an absorber. When the substrate 710 is Si glass, an absorber that selectively absorbs blue light for each wavelength region may be, for example, a material including Na, K, and Zn. Alternatively, YT-245 (ADEKA ARLKS, λ _max = 430 nm) or GPX-201 (ADEKA ARLKS, λ _max = 493 nm), which is a visible light absorbing dye, may be used as an absorber that absorbs blue light.

According to an embodiment of the present invention, a desired level of transmittance can be obtained for each wavelength region by adjusting the concentration and the ratio of the absorber.

9 is a graph for setting the transmittance of blue light for each wavelength region according to an embodiment of the present invention.

Referring to FIG. 9, the substrate 710 or the coating layer 730 may be set to have a transmittance of 10% to 40% within a range of 415 nm to 495 nm. For example, the transmittance for the first wavelength region having a wavelength of 415 nm to 450 nm may be set to 10% to 25%, and the transmittance for the second wavelength region having a wavelength of 450 nm to 495 nm may be set to 25% to 40%. have.

The blue light transmittance at the center of the 430nm CUT IR filter is about 21%, the blue light transmittance at the periphery is about 26%, the blue light transmittance at the center of the 460nm CUT IR filter is about 4%, and the blue light transmittance at the periphery is about 21%. As described above, the IR filter designed to block all light below a specific wavelength has a high blue light transmittance at both the center and the periphery, or a large blue light transmittance difference at the center and the periphery.

On the contrary, when the transmittance of the blue light for each wavelength region is set as shown in FIG. 9, the IR filter can maintain the transmittance of the blue light appropriately to reduce color bleeding while maintaining the central and peripheral images uniformly.

Meanwhile, according to one embodiment of the present invention, the thickness of the coating layer 730 may be adjusted to set the transmittance for each wavelength region within a range of 415 nm to 495 nm.

That is, as shown in FIGS. 5 and 6, the light passing through the optical filter 700 undergoes a wavelength shift according to the incident angle. In order to reduce the wavelength shift according to the incident angle, the thickness of the coating layer may be set thicker from the center of the coating layer 730 toward the peripheral portion.

To this end, at least one of the at least one first thin film layer and the at least one second thin film layer may be set to become thicker from the central portion to the periphery. Accordingly, the reflectance or transmittance of the blue light can be optimized in each of the region having a small incident angle and the region having a large incident angle.

In general, the thickness of at least one of the first thin film layer and the second thin film layer may be designed to a thickness of 0.15 to 0.35 times the wavelength to be blocked, preferably 0.2 to 0.3. Accordingly, at least one of the at least one first thin film layer and the at least one second thin film layer may be formed to a thickness of 0.15 to 0.35 times, preferably 0.2 to 0.3 times, of 415 nm to 495 nm.

In addition, at least one of the at least one first thin film layer and the at least one second thin film layer may have a thickness of 0.15 to 0.35 times, preferably 0.2 to 0.3 times, between 415 nm and 450 nm, and Located at the edge, it may include a second region formed to a thickness of 0.15 to 0.35 times, preferably 0.2 to 0.3 times of 450nm to 495nm.

In this case, the thickness of the first thin film layer and the second thin film layer may be set in consideration of the refractive index of the material included in each thin film layer. For example, as shown in FIG. 8, the ratio of the regulation ratio of TiO 2 to SiO 2 at 430 nm is 3.15 / 1.55, and the ratio of the regulation ratio of TiO 2 to SiO 2 at 460 nm is 3.1 / 1.55. Accordingly, at least one of the first thin film layer and the second thin film layer is formed to a thickness of 0.15 to 0.35 times, preferably 0.2 to 0.3 times, of 415 nm to 450 nm in the first region, and 0.15 to 450 times of 450 nm to 495 nm in the second region. The thickness of the second thin film layer is 0.35 times, preferably 0.2 to 0.3 times, and the thickness of the second thin film layer is set to be 3.15 / 1.55 times the thickness of the first thin film layer in the first region, and 3.1 / 1.55 of the thickness of the first thin film layer in the second region. The thickness of the second thin film layer may be set to double.

Accordingly, as shown in FIG. 10, an optical filter having a minimum wavelength shift according to an incident angle within a range of 415 nm to 495 nm may be obtained.

Meanwhile, the IR filter according to the embodiment of the present invention is illustrated as including a substrate, a buffer layer, and a coating layer, but is not limited thereto. The IR filter may not include a buffer layer and a coating layer. In this case, the IR filter may include a substrate including an absorber absorbing near infrared rays and an absorber having a different transmittance for each wavelength region in a range of 415 nm to 495 nm. The absorber absorbing near infrared rays may include, for example, a P ₂ O ₅ based material.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

100: camera module
110: printed circuit board
120: image sensor
130: IR filter
140: lens assembly
150: lens holder
700: optical filter
710: substrate
720: buffer layer
730: coating layer

Claims (13)

Board,
A buffer layer formed on the substrate, and
A coating layer formed on the buffer layer, wherein the first thin film layer and the second thin film layer having different refractive indices are alternately formed at least two times,
The transmittance for each wavelength region is set to be different within a range of 415 nm to 495 nm,
The coating layer is thicker from the center toward the periphery,
At least one of the at least one first thin film layer and the at least one second thin film layer is formed to a thickness of 0.15 to 0.35 times of 415 nm to 495 nm,
At least one of the at least one first thin film layer and the at least one second thin film layer
A first region formed to a thickness of 0.15 to 0.35 times of 415 nm to 450 nm, and
An optical filter including a second region positioned at an edge of the first region and formed to a thickness of 0.15 to 0.35 times of 450 nm to 495 nm. The method of claim 1,
The substrate includes an absorber configured to vary the transmittance for each wavelength region within a range of 415 nm to 495 nm. The method of claim 2,
The substrate has an optical filter having a transmittance of 10% to 40% within a wavelength range of 415 nm to 495 nm. The method of claim 3,
The transmittance for the first wavelength region having a wavelength of 415 nm to 450 nm is 10% to 25%,
An optical filter having a transmittance of 25% to 40% for a second wavelength region having a wavelength of 450 nm to 495 nm. The method of claim 4, wherein
The substrate further comprises an absorber for absorbing near infrared rays. delete delete delete The method of claim 1,
The first thin film layer comprises TiO ₂ , and the second thin film layer comprises SiO ₂ . Printed circuit board,
An image sensor mounted on the printed circuit board and connected to the printed circuit board by a wire;
An optical filter formed on the image sensor and set to have a different transmittance for each wavelength region within a range of 415 nm to 495 nm;
A lens assembly formed on the optical filter, and
A lens holder incorporating and supporting the optical filter and the lens assembly;
The optical filter is
Board,
A buffer layer formed on the substrate, and
A coating layer formed on the buffer layer, wherein the first thin film layer and the second thin film layer having different refractive indices are alternately formed at least two times,
The transmittance for each wavelength region is set to be different within a range of 415 nm to 495 nm,
The coating layer is thicker from the center toward the periphery,
At least one of the at least one first thin film layer and the at least one second thin film layer is formed to a thickness of 0.15 to 0.35 times of 415 nm to 495 nm,
At least one of the at least one first thin film layer and the at least one second thin film layer is a first region formed to a thickness of 0.15 to 0.35 times of 415 nm to 450 nm, and
And a second region positioned at an edge of the first region and formed to a thickness of 0.15 to 0.35 times of 450 nm to 495 nm. The method of claim 10,
The lens assembly includes a lens formed with a diffractive optical element (DOE) pattern. delete delete

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