KR20240047953A - Lens system for image acquisition - Google Patents

Abstract

The present invention relates to a lens system for image capture including a plurality of lenses arranged sequentially from an object side surface to an image side surface, the lens system comprising: a first lens having negative refractive power; A second lens having negative refractive power and made of plastic; A third lens having positive refractive power and made of plastic; An aperture disposed between the third lens and the fourth lens; a fourth lens having positive refractive power, both the object side surface and the image side surface being spherical and made of glass; A fifth lens having positive refractive power and made of plastic; And, a sixth lens having negative refractive power and made of plastic, wherein the focal length of the entire lens system is f, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f2. The focal length is f4, the focal length of the fifth lens is f5, and each focal length is 2.0 < f4/f < 2.5, -3.0 < f3/f2 < -2.0, 1.0 < f4/f5 < 1.5, -2.0 < f6/f5 < Constructed to satisfy -1.5, it can be supplied at a cost of about 50% compared to using existing glass lenses, and even when using plastic lenses, it can be used in a temperature range of -40℃ to 125℃, and has a resolution of 4M or higher. A lens system for image taking may be provided.

Description

Lens system for image acquisition {LENS SYSTEM FOR IMAGE ACQUISITION}

The present invention relates to a lens system for image capture. More specifically, 4 out of 6 lenses are made up of plastic lenses, which is very inexpensive compared to existing glass lenses and has a 4M class rating even in the temperature range of -40℃ to 125℃. This relates to a lens system for image capture that can guarantee high-resolution resolution.

Recently, with the Fourth Industrial Revolution, the industrial sector is facing a period of upheaval as technologies such as artificial intelligence (AI), Internet of Things (IoT), cloud, and 5G begin to spread around the world. In particular, in the automobile industry, the demand for verification of the performance and safety of optical module-related components is increasing due to the formation of new markets such as electric vehicles, hydrogen vehicles, and autonomous vehicles.

Among optical module-related parts, the lens module in particular is a key element that can determine the performance of a camera. Recently, more and more cameras are being introduced as part of vehicles. Rear-view cameras are already commonly found around us, and vehicles with cameras located on the side of the vehicle instead of side mirrors are being introduced one after another on the market. In addition, not only in autonomous vehicles, but also cameras are installed inside and outside the vehicle instead of the driver's perspective, becoming an essential component for detecting lanes and the distance to the vehicle in front.

The lens module is configured to arrange multiple lenses. In the harsh environments of automobiles, such as near the polar regions or near the equator, the refractive index, curvature, and lens thickness of the optical elements change due to temperature changes inside and outside the automobile, and the gap due to contraction and expansion of the barrel components. There was a problem that the performance of the optical module deteriorated due to the change. Accordingly, glass lenses were mainly used as lenses that could withstand harsh environments, but when glass lenses were used, there were problems with processing difficulties, weight reduction, and high prices.

Chinese Patent Publication No. 112649950 (2021.04.13) “Lens” Japanese Patent No. 7172553 (2022.11.16) “Lens module and vehicle imaging device”

The object of the present invention is to solve the conventional problems as described above. By applying a hybrid-based optical system employing a plastic lens, a lens for image capture can be supplied at a cost of about 50% compared to the case of using a conventional glass lens. To provide a system.

In addition, it provides a lens system for image capture that can be used in a temperature range of -40℃ to 125℃ even when using a plastic lens.

In addition, a hybrid-based optical system is applied to provide a lens system for image capture with a resolution of 4M or higher.

The above problem is, according to the present invention, to provide a lens system for image capture including a plurality of lenses sequentially arranged from the object side surface to the image side surface, the first lens having negative refractive power; A second lens having negative refractive power and made of plastic; A third lens having positive refractive power and made of plastic; An aperture disposed between the third lens and the fourth lens; a fourth lens having positive refractive power, both the object side surface and the image side surface being spherical and made of glass; A fifth lens having positive refractive power and made of plastic; And, a sixth lens having negative refractive power and made of plastic, wherein the focal length of the entire lens system is f, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f2. The focal length is f4, the focal length of the fifth lens is f5, and each focal length is 2.0 < f4/f < 2.5, -3.0 < f3/f2 < -2.0, 1.0 < f4/f5 < 1.5, -2.0 < f6/f5 < This can be achieved by a lens system for image taking configured to satisfy -1.5.

Here, the distance between the fifth lens and the sixth lens on the optical axis may be 0.5 mm or less.

Additionally, the first lens may be made of glass or polymer.

Additionally, the Abbe number (vd5) of the fifth lens and the Abbe number (vd6) of the sixth lens may satisfy vd5 > 50 and vd6 < 30.

Additionally, the Fno of the lens system may be 2.2 or less.

Additionally, the use temperature range of the lens system may be -45 to 105°C.

According to the present invention, a lens system for image capture is provided that can be supplied at a cost of about 50% compared to the case of using a conventional glass lens by applying a hybrid-based optical system employing a plastic lens.

In addition, a lens system for image capture that can be used in a temperature range of -40℃ to 125℃ is provided even when using a plastic lens.

In addition, a lens system for image capture with a resolution of 4M or higher is provided by applying a hybrid-based optical system.

1 is a schematic diagram of a lens system for image pickup according to a first embodiment of the present invention;
FIG. 2 is a graph of the aberration characteristics of the lens system of FIG. 1.

Prior to description, in various embodiments, components having the same configuration will be described using the same symbols.

Hereinafter, a lens system for image capture according to a first embodiment of the present invention will be described in detail with reference to the attached drawings.

The first lens refers to the lens closest to the object side, and the sixth lens refers to the lens closest to the image sensor.

In each lens, the first surface refers to the surface close to the object side (or, the object side surface), and the second surface refers to the surface close to the image side (or, the image side surface). In addition, in this specification, the values for the radius of curvature of the lens, thickness, image height (IMGH, 1/2 of the diagonal length of the image sensor's imaging surface), etc. are all in mm units, and FOV (angle of view of the imaging optical system) The unit is Degree.

In addition, in the description of the shape of each lens, the shape that one side is convex means that the paraxial region of the surface is convex, and the shape that one side is concave means that the paraxial region of the surface is concave. Therefore, even if one surface of the lens is described as having a convex shape, the edge portion of the lens may be concave. Likewise, even if one side of the lens is described as having a concave shape, the edge of the lens may be convex. The paraxial region refers to a very narrow area near the optical axis.

A lens system for image taking according to an embodiment of the present invention includes six lenses. For example, the lens system for image capture according to an embodiment of the present invention includes a first lens, a second lens, a third lens, an aperture, a fourth lens, a fifth lens, and a sixth lens arranged in order from the object side. It consists of:

Additionally, the lens system for image capturing of the present invention may further include an image sensor for converting an image of an incident subject into an electrical signal. Additionally, an aperture may be further included to control the amount of light. For example, the aperture may be disposed between the third and fourth lenses.

Some of the first to sixth lenses constituting the lens system for image capture according to an embodiment of the present invention may be made of plastic materials, and the remainder may be made of glass or polymer materials. Additionally, lenses made of glass or polymer may have different optical characteristics from lenses made of plastic.

For example, the first and fourth lenses may be made of glass or polymer, and the second, third, fifth, and sixth lenses may be made of plastic.

In addition, some of the first to seventh lenses constituting the lens system for image capture according to an embodiment of the present invention may be aspherical lenses, and the remainder may be spherical lenses.

For example, the first and second surfaces of the first and fourth lenses may be spherical, respectively. The first and second surfaces of the second lens, third lens, fifth lens, and sixth lens may be aspherical.

That is, the first lens and fourth lens are made of glass or polymer and the first and second surfaces are spherical, and the third, fifth, and sixth lenses are made of plastic and have first and second surfaces. The surface may be configured as an aspherical surface.

The aspheric surface is expressed by Equation 1 below.

In Equation 1, Z is the distance from any point on the aspherical surface of the lens to the vertex of the aspherical surface, c is the reciprocal of the radius of curvature (r) of the lens, K is the Conic constant, and Y is an arbitrary point on the aspherical surface of the lens. It represents the distance from the point to the optical axis. In addition, the constants A to E refer to the aspheric coefficient.

The imaging optical system consisting of the first to sixth lenses may have refractive powers of negative/negative/positive/positive/positive/negative in that order from the object side.

Meanwhile, the lens system for image capturing according to an embodiment of the present invention can satisfy the following conditional expressions.

[Conditional Expression 1] TTL/(2*IMGH) < 2.75

[Conditional Expression 2] 2.0 < f4/f < 2.5

[Conditional Expression 3] -3.0 < f3/f2 < -2.0

[Conditional Expression 4] 1.0 < f4/f5 < 1.5

[Conditional Expression 5] -2.0 < f6/f5 < -1.5

[Conditional Expression 6] vd5 > 50

[Conditional Expression 7] vd6 > 30

[Conditional Expression 8] P5 thi ≤ 0.5

In the conditional expressions, TTL is the distance from the object side of the first lens to the imaging surface of the image sensor, IMGH is 1/2 of the diagonal length of the imaging surface of the image sensor, f is the focal length of the entire lens system, and f2 is the distance of the second lens. Focal length, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, vd5 is the Abbe number of the fifth lens, vd6 is the Abbe number of the sixth lens, P5 thi is the distance between the 5th lens and the 6th lens.

Chromatic aberration correction performance can be improved by setting the Abbe number and distance between the fifth and sixth lenses.

As such, the lens system for image capture of the present invention consists of a total of 6 lenses, of which 4 plastic lenses are used, thereby ensuring a high resolution of 4M and reducing production costs.

In addition, the first and fourth lenses are made of glass or polymer material with a relatively small thermal expansion coefficient, and the second, third, fifth, and sixth lenses are made of plastic, realizing wide-angle high resolution. At the same time, resolution can be guaranteed even over a wide range of temperature changes (-45℃ to 105℃).

Additionally, the lens system for image capture has an fno (a constant representing the brightness of the lens system) of 2.2 or less, so objects can be captured clearly even in low-light environments.

Meanwhile, the housing where the first to sixth lenses are disposed is made of plastic material, and the housing contracts or expands depending on temperature changes in the surrounding environment. Therefore, the distance between the sixth lens and the image sensor changes due to deformation of the housing due to temperature changes, which may ultimately cause problems with poor focus.

However, in the lens system for image capturing according to an embodiment of the present invention, the second lens, third lens, fifth lens, and sixth lens are formed of plastic material, so depending on temperature changes in the surrounding environment, the second lens, The third lens, fifth lens, and sixth lens contract or expand.

Therefore, by designing the amount of deformation of the second lens, third lens, fifth lens, and sixth lens in consideration of the amount of shape deformation of the housing due to temperature change, the focus position can be configured not to change even if there is a temperature change.

That is, the lens system for image capture according to an embodiment of the present invention may be configured such that the amount of change in distance between the sixth lens and the image sensor according to temperature change corresponds to the amount of change in focus position due to temperature change.

FIG. 1 is a schematic diagram of a lens system for image pickup according to a first embodiment of the present invention, and FIG. 2 is a graph of aberration characteristics of the lens system of FIG. 1.

Referring to Figure 1, the imaging optical system according to the first embodiment of the present invention includes a first lens 100, a second lens 200, a third lens 300, a fourth lens 400, and a fifth lens ( 500) and an optical system including a sixth lens 600, an aperture (ST), an optical filter 700, and an image sensor 800.

The lens characteristics (radius of curvature, thickness of the lens or distance between lenses, index of refraction, Abbe number) of each lens are shown in Table 1.

The height (IMGH) is 5.87 mm.

In the surface numbers in Table 1 above, * indicates an aspherical surface.

The first lens 100 has negative refractive power and has a meniscus shape convex toward the object. For example, the first surface 1 of the first lens 100 is convex in the paraxial region, and the second surface 2 of the first lens 100 is concave in the paraxial region.

The second lens 200 has negative refractive power and has a meniscus shape convex toward the object. For example, the first surface 4 of the second lens 200 is convex in the paraxial region, and the second surface 5 of the second lens 200 is concave in the paraxial region.

The third lens 300 has positive refractive power and has a meniscus shape convex toward the object. For example, the first surface 7 of the third lens 300 is convex in the paraxial region, and the second surface 8 of the third lens 300 is concave in the paraxial region.

The fourth lens 400 has positive refractive power and has a shape where both sides are convex. For example, the first surface 10 and the second surface 11 of the fourth lens 400 have a convex shape in the paraxial region.

The fifth lens 500 has positive refractive power and has a shape where both sides are convex. For example, the first surface 13 and the second surface 14 of the fifth lens 500 have a convex shape in the paraxial region.

The sixth lens 600 has negative refractive power and has a concave shape on both sides. For example, the first surface 15 and the second surface 16 of the sixth lens 600 have a concave shape in the paraxial region.

Additionally, the first lens 100 is located closest to the external environment and may be made of glass or a polymer material similar to glass to withstand external scratches and humidity and to converge wide-angle light. The fourth lens 400 is made of a glass material whose object-side surface and image-side surface are both aspherical. Since the fourth lens 400 functions as a converging lens, it can minimize deformation due to temperature changes by being made of glass.

Meanwhile, the first and second surfaces of the second lens 200, third lens 300, fifth lens 500, and sixth lens 600 have aspheric coefficients as shown in Tables 2 and 3. has

2nd lens Third lens 4 5 7 8 K -2.09007413E+00 -2.20264825E+72 -2.55626514E+00 -1.87330782E+00 A 2.76821868E-04 3.61016944E-04 -1.41634802E-03 -1.12056108E-03 B -4.68149076E-07 -1.10811800E-06 3.30960876E-06 -6.56010243E-03 C 4.01292143E-09 -5.88144256E-07 2.30041427E-06 1.82777282E-05 D -2.59878489E-10 4.65455107E-08 -1.37951719E-07 -1.66848032E-06 E 5.93042472E-11 -1.41916301E-09 4.34544722E-09 8.29509373E-08

5th lens 6th lens 13 14 15 16 K -1.12692601E+48 1.19945747E+00 -4.03724774E+00 3.12834834E+00 A 1.68694048E-03 1.22305453E-03 -1.55135099E-05 -8.30433796E-05 B -2.03624181E-04 -1.25001410E-04 1.194814112E-05 1.21631324E-05 C 1.79548226E-05 4.81806295E-06 -4.20412798E-06 -1.60497430E-06 D -8.90787993E-07 3.28191660E-07 3.65718855E-07 1.04925984E-07 E 2.20436466E-08 -4.15727200E-08 -1.68188792E-08 -4.00249344E-09

The second lens 200, third lens 300, fifth lens 500, and sixth lens 600 are aspherical lenses and are made of plastic material. Here, the second lens 200, third lens 300, fifth lens 500, and sixth lens 600 may be made of plastic material with the same optical characteristics.

Meanwhile, the Abbe number (vd5) of the fifth lens 500 exceeds 50, the Abbe number (vd6) of the sixth lens 600 is less than 30, and the fifth lens 500 and the sixth lens ( 600) The chromatic aberration correction performance can be improved by installing the distance (P5 thi) to be less than 0.5 mm.

And, the aperture ST may be disposed between the third lens 300 and the fourth lens 400.

An optical filter 700 may be positioned between the sixth lens 600 and the image sensor 800. An infrared filter, a cover glass, etc. may be used as the optical filter 700, and such optical filters are not considered to affect optical performance.

The lens system for image pickup according to the first embodiment of the present invention as described above may have aberration characteristics as shown in FIG. 2.

The scope of the present invention is not limited to the above-described embodiments, but may be implemented in various forms of embodiments within the scope of the appended claims. It is considered to be within the scope of the claims of the present invention to the extent that anyone skilled in the art can make modifications without departing from the gist of the invention as claimed in the claims.

※Explanation of symbols for main parts of the drawing※
100: first lens 200: second lens
300: Third lens 400: Fourth lens
500: 5th lens 600: 6th lens
700: Optical filter 800: Image sensor
ST: Aperture

Claims (6)

In a lens system for image taking including a plurality of lenses arranged sequentially from the object side to the image side,
A first lens having negative refractive power;
A second lens having negative refractive power and made of plastic;
A third lens having positive refractive power and made of plastic;
An aperture disposed between the third lens and the fourth lens;
a fourth lens having positive refractive power, both the object side surface and the image side surface being spherical and made of glass;
A fifth lens having positive refractive power and made of plastic; and,
It has negative refractive power and includes a sixth lens made of plastic,
The focal length of the entire lens system is f, the focal length of the second lens is f2, the focal length of the third lens is f3, the focal length of the fourth lens is f4, and the focal length of the fifth lens is f5,
A lens system for image capture where each focal length satisfies the following: 2.0 < f4/f < 2.5, -3.0 < f3/f2 < -2.0, 1.0 < f4/f5 < 1.5, -2.0 < f6/f5 < -1.5. According to paragraph 1,
A lens system for image capture wherein the distance between the fifth lens and the sixth lens on the optical axis is 0.5 or less. According to paragraph 1,
A lens system for image capture wherein the first lens is made of glass or polymer. According to paragraph 1,
A lens system for image capture where the Abbe number (vd5) of the fifth lens and the Abbe number (vd6) of the sixth lens satisfy vd5 < 30 and vd6 > 50. According to paragraph 1,
A lens system for image capture where the Fno of the lens system is 2.2 or less. According to paragraph 1,
A lens system for image capture with a temperature range of -45 to 105°C.