TWI873226B - Optical system and camera module for comprising the same - Google Patents

Abstract

A zoom optical system according to an embodiment of the present invention includes a first lens group, a second lens group, a third lens group, and a fourth lens group which are sequentially disposed in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, a total track length (TTL) is less than 20 mm, and an effective focal length (EFL) in a telephoto is greater than 25 mm.

Description

Optical system and camera module including the optical system

The present invention relates to an optical system and a camera module including the optical system.

As the performance of camera modules embedded in portable terminals develops, camera modules in portable terminals also require autofocus functions.

In the process of converting external light into digital images or digital video so that the camera module in the portable terminal has an auto focus function, the magnification can be increased by a digital process. Therefore, it is possible to zoom only at predetermined magnifications such as 1x, 3x, and 5x, and there is a problem of digital degradation as the magnification increases.

At the same time, in order to enable the camera module in the portable terminal to have an autofocus function, a technology of moving the lens to adjust the distance between the lens and the image sensor is attempted. However, it is difficult to design an optical system that can move in the small space in the portable terminal.

The present invention relates to providing a zoom optical system and a camera module including the zoom optical system.

The objectives to be solved by the present invention are not limited to those described above, and include purposes or effects that can be understood based on the solutions or embodiments described below.

One aspect of the present invention provides a zoom optical system, which includes a first lens group, a second lens group, a third lens group and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, a total track length (TTL) is less than 20mm, and an effective focal length (EFL) in a telephoto lens is greater than 25mm.

The EFL in the telephoto can be 1.5 times greater than an EFL in a wide angle.

A moving stroke of the second lens group can be less than 2.5 mm during zooming from the wide angle to the telephoto.

The second lens group and the third lens group may include at least one glass lens.

The glass lens may have a refractive index greater than 1.7, or an Abbe number greater than 60.

The lenses included in the first lens group to the fourth lens group may be D-cut lenses.

The second lens group and the third lens group may include lenses in which a value obtained by dividing a length of a major axis of an effective diameter by a length of a minor axis of the effective diameter is 1.

A chief ray angle (CRA) can be less than 6°.

The zoom optical system may further include a right-angle prism arranged in sequence in front of the first lens group in the direction from the object side to the image side.

A value obtained by dividing the EFL by an f-number can be greater than 6 in the telephoto.

In the telephoto, the EFL can be greater than 25mm and an f-number can be less than 4.2.

Another aspect of the present invention provides a zoom optical system, which includes a first lens group, a second lens group, a third lens group and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, and in a telephoto, an EFL is greater than 25mm, and an f-number is less than 4.2.

Another aspect of the present invention provides a zoom optical system, which includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, and a value obtained by dividing an EFL by an f-number is greater than 6 in a telephoto.

According to the embodiment, an optical system capable of zooming at high magnification in addition to low magnification and a camera module including the optical system can be obtained. In the optical system according to one embodiment of the present invention, the zoom can be adjusted continuously, high resolution can be maintained even at high magnification, f-number can be maintained even at long focal length, low chief ray angle (CRA) can be maintained, and thus an optical system with compact size can be designed.

10: Image sensor

20: Filter

100: First lens group

110: Lens

112: Object side surface

114: Image side surface

120: Lens

122: Object side surface

124: Convex image side surface

130: Lens

132: Side surface of concave object

134: Image side surface

200: Second lens group

210: Lens

212: Object side surface

214: Convex image side surface

220: Lens

222: Side surface of convex object

224: Concave image side surface

300: The third lens group

310: Lens

312: Side surface of convex object

314: Convex image side surface

320: Lens

322: Side surface of concave object

324: Concave image side surface

400: The fourth lens group

410: Lens

412: Side surface of convex object

414: Convex image side surface

1000: zoom optical system

1100: Main camera module

2000: Camera module

d1a: distance

d2a: distance

d3a: distance

d1b: distance

d2b: distance

d1c: distance

d2c:Distance

d3c:Distance

f: focal length

h: height

l: length

w: width

FIG1 is a diagram illustrating a zoom optical system according to an embodiment of the present invention.

FIG. 2A is a cross-sectional view of a zoom optical system at a wide angle according to the first embodiment of the present invention.

FIG. 2B is a cross-sectional view of a zoom optical system in an intermediate mode according to the first embodiment of the present invention.

FIG2C is a cross-sectional view of a zoom optical system at a telephoto position according to the first embodiment of the present invention.

FIG. 3A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in a wide-angle optical system for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the first embodiment.

FIG. 3B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system in an intermediate mode for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the first embodiment.

FIG. 3C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at a telephoto focal length for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the first embodiment.

FIG4A is a cross-sectional view of a zoom optical system at a wide angle according to the second embodiment of the present invention.

FIG4B is a cross-sectional view of a zoom optical system in an intermediate mode according to the second embodiment of the present invention.

FIG. 4C is a cross-sectional view of a zoom optical system at a telephoto position according to the second embodiment of the present invention.

FIG. 5A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in a wide-angle optical system for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the second embodiment.

FIG. 5B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system in an intermediate mode for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the second embodiment.

FIG. 5C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in a telephoto optical system for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the second embodiment.

FIG6A is a cross-sectional view of a zoom optical system at a wide angle according to the third embodiment of the present invention.

FIG6B is a cross-sectional view of a zoom optical system in an intermediate mode according to the third embodiment of the present invention.

FIG6C is a cross-sectional view of a zoom optical system at a telephoto position according to the third embodiment of the present invention.

FIG. 7A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in a wide-angle optical system for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the third embodiment.

FIG. 7B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system in an intermediate mode for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the third embodiment.

FIG. 7C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in a telephoto optical system for light of wavelengths of 435 nm, 486 nm, 546 nm, 587 nm and 656 nm according to the third embodiment.

FIG8 is a view illustrating a portion of a portable terminal, in which a camera module according to an embodiment of the present invention is applied.

FIG. 9 is a view of a camera module including a zoom optical system according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the technical spirit of the present invention is not limited to some embodiments, which will be described and can be implemented using various other embodiments, and at least one component of the embodiment can be selectively coupled, replaced and used to implement the technical spirit within the scope of the technical spirit.

In addition, unless otherwise clearly and specifically defined by the context, all terms used herein (including technical and scientific terms) may be interpreted as having the meanings customarily used by those skilled in the art, and the meanings of commonly used terms, such as those defined in commonly used dictionaries, will be interpreted in consideration of the contextual meanings of the relevant art.

Additionally, the terms used in the embodiments of the present invention are considered in a descriptive sense and do not limit the present invention.

In this specification, unless the context clearly indicates otherwise, the singular form includes its plural form, and in the case of describing "at least one (or one or more) of A, B and C", this may include at least one combination of all combinations that can be combined with A, B and C.

In describing the components of the present invention, terms such as "first", "second", "A", "B", "(a)", and "(b)" may be used.

These terms are used only to distinguish one element from another, and the nature, order, etc. of the elements are not limited by these terms.

It should be understood that when an element is referred to as being "connected or coupled" to another element, the description may include both a situation in which the element is directly connected or coupled to another element and a situation in which the element is connected or coupled to the other element via another element disposed between the element and the other element.

Where any element is described as being formed or disposed "on or under another element", this description includes both a condition where two elements are formed or disposed in direct contact with each other and a condition where one or more other elements are interposed between the two elements. In addition, when an element is described as being formed "on or under another element", this description may include a condition where one element is formed at the upper side or the lower side relative to the other element.

FIG1 is a diagram illustrating a zoom optical system according to an embodiment of the present invention.

Referring to FIG. 1 , the zoom optical system according to an embodiment of the present invention includes a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400, which are arranged in sequence from the object side to the image side.

According to an embodiment of the present invention, the first lens group 100 includes a plurality of lenses and is fixed. That is, the plurality of lenses 110, 120, and 130 are fixed. In this case, the first lens group 100 may include at least three lenses 110, 120, and 130. In a case where the first lens group 100 includes two or less lenses, it may be difficult to correct the resolution at the maximum magnification, and in a case where the first lens group 100 includes four or more lenses, since the total size of the zoom optical system may increase, the first lens group 100 may preferably include three lenses.

The second lens group 200 includes at most two lenses 210 and 220 and is movable. That is, the two lenses 210 and 220 can move together along the central axis of the lens. When the second lens group 200 moves, the focal length can be adjusted in sequence. When the second lens group 200 moves, the magnification can be adjusted in sequence. Therefore, the second lens group 200 can act as a zoom group.

The third lens group 300 includes at most two lenses 310 and 320 and is movable. That is, the two lenses 310 and 320 can move together along the central axis of the lens. When the third lens group 300 moves, its focus can be adjusted. In addition, the third lens group 300 can serve as a focusing group.

In the case where the second lens group 200 includes three or more lenses or the third lens group 300 includes three or more lenses, the size and weight of the second lens group 200 or the third lens group 300 may increase, and the driving power may increase when the second lens group 200 or the third lens group 300 moves.

According to the movement of the second lens group 200 and the third lens group 300, the magnification of the zoom optical system can be continuously increased or decreased within a range of 5 times to 7.5 times, for example. In this case, the continuous increase or decrease of the magnification does not refer to the intermittent increase or decrease of the magnification in a digital manner, but may refer to a linear decrease or decrease therein.

Each of the second lens group 200 and the third lens group 300 can be independently moved. For example, when the wide angle is changed to the telephoto, the distance between the second lens group 200 and the third lens group 300 can increase in the direction from the movement starting point (wide angle starting point) to the predetermined point, and decrease in the direction from the predetermined point to the movement end point (telephoto end point).

The fourth lens group 400 includes a lens 410, and the lens 410 is fixed.

According to an embodiment of the present invention, the filter 20 and the image sensor 10 can be sequentially arranged behind the third lens group 300. In this case, the filter 20 can be an infrared (IR) filter. Therefore, the filter 20 can block near-IR light (e.g., light with a wavelength of 700nm to 1100nm) from being incident on the camera module. In addition, the image sensor 10 can be connected to the printed circuit board by wires.

Alternatively, the filter 20 may also include a foreign matter blocking filter and an IR filter sequentially arranged in the direction from the object side to the image side. In the case where the filter 20 includes a foreign matter blocking filter, foreign matter generated when the third lens group 300 moves can be prevented from being introduced into the IR filter or the image sensor 10.

According to an embodiment of the present invention, in a zoom optical system, the total track length (TTL) may be less than 20 mm. Here, TTL may refer to the length from the surface of the image sensor to the first surface of the zoom optical system. For example, TTL may refer to the length from a surface of the first lens group 100 closest to the object side to the upper surface of the image sensor 10 on which light is incident. In this specification, TTL may be interchangeable with total length.

According to an embodiment of the present invention, in a zoom optical system, the effective focal length (EFL, f) in telephoto can be greater than 25 mm. The EFL of the zoom optical system in wide angle can be less than 17.5 mm. In a zoom optical system, the EFL in telephoto can be greater than 1.5 times the EFL in wide angle.

According to an embodiment of the present invention, in a zoom optical system, the f-number (Fno) in telephoto may be less than 4.2. In this case, the f-number may refer to the ratio (f/D) of the focal length (f) to the effective diameter (D) of the aperture. When the f-number decreases, the amount of light collected increases, so that the image may be brightened, and when the f-number increases, the amount of light collected decreases, so that the image may be darkened. Therefore, in a zoom optical system according to an embodiment of the present invention, since the f-number is less than 4.2 even at a long distance of more than 25 mm in telephoto, a predetermined brightness can be maintained.

According to an embodiment of the present invention, in a zoom optical system, the ratio of focal length to f-number at maximum magnification (f/Fno) can be greater than 6. That is, since the f-number is smaller than the focal length, a predetermined brightness can be maintained even at a high magnification.

According to an embodiment of the present invention, the moving stroke of the second lens group 200 may be less than 2.5 mm. In this case, the moving stroke may refer to the distance in which the lens group can be moved by the driving portion. Therefore, when the mode of the second lens group 200 is changed from telephoto to wide angle (from wide angle to telephoto), the second lens group can be moved in a unit of less than 2.5 mm. In a case where the moving stroke is greater than 2.5 mm or more, since the size of the driving portion for moving the lens group is excessively increased, there is a problem that it is difficult to install the camera module in a portable terminal. However, since the moving stroke is implemented to be less than 2.5 mm, the camera module can be miniaturized.

According to an embodiment of the present invention, in at least one of the lenses 210, 220, 310, and 320 included in the second lens group 200 and the third lens group 300, the refractive index may be greater than 1.7, or the Abbe number may be greater than 60. That is, in at least one of the plurality of lenses 210 and 220 included in the second lens group 200, the refractive index may be greater than 1.7, or the Abbe number may be greater than 60, and in at least one of the plurality of lenses 310 and 320 included in the third lens group 300, the refractive index may be greater than 1.7, or the Abbe number may be greater than 60. At least one of the plurality of lenses 210, 220, 310 and 320 included in the second lens group 200 and the third lens group 300 may be a glass lens. A lens having a refractive index greater than 1.7 or an Abbe number greater than 60 may be a glass lens. According to an embodiment of the present invention, by using a glass lens, the volume of the zoom optical system can be reduced, and therefore, the movable distance of the second lens group 200 and the third lens group 300, that is, the number of strokes, can be reduced. In addition, by using a glass lens, chromatic aberration can be reduced and the refractive index can be increased, so that performance can be improved.

According to an embodiment of the present invention, the plurality of lenses 110, 120, 130, 210, 220, 310, 320 and 410 included in the first lens group 100 to the fourth lens group 400 may be lenses to which D-cut technology is applied. Each of the plurality of lenses 110, 120, 130, 210, 220, 310, 320 and 410 included in the first lens group 100 to the fourth lens group 400 may be a D-cut lens in which a portion of the upper portion and a portion of the lower portion are cut. In this case, the ribs and portions of the upper and lower portions in the effective diameter of each of the plurality of lenses 110, 120, 130, 210, 220, 310, 320, and 410 may be cut, or only the ribs may be cut without cutting the effective diameter. According to one embodiment, the second lens group 200 and the third lens group may include lenses in which the value obtained by dividing the length of the major axis of the effective diameter by the length of the minor axis of the effective diameter is 1. That is, the length of the major axis of the effective diameter and the length of the minor axis of the effective diameter may be the same. For example, in the case of the fifth lens 220, the sixth lens 310, and the seventh lens 320, only the ribs of the upper and lower portions may be cut and the effective diameter may not be cut. In a circular type lens, there is a problem that the volume increases due to the vertical height, but since the D-cut technology is applied to the upper and lower portions of each of the plurality of lenses 110, 120, 130, 210, 220, 310, 320, and 410, the vertical height can be reduced, so that the volume of the lens can be reduced.

The magnification can be changed according to the distance between the first lens group 100 and the second lens group 200, the distance between the second lens group 200 and the third lens group 300, and the distance between the third lens group 300 and the fourth lens group 400.

According to an embodiment of the present invention, in a zoom optical system, the chief ray angle (CRA) can be less than 6. Therefore, since the angle of light incident on the image sensor 10 is smaller, the degree of freedom of sensor selection can be improved, and a zoom optical system with a more compact size can be obtained.

Hereinafter, the present invention will be described with reference to various embodiments.

FIG. 2A is a cross-sectional view of a zoom optical system at a wide angle according to the first embodiment of the present invention, FIG. 2B is a cross-sectional view of a zoom optical system at an intermediate mode according to the first embodiment of the present invention, and FIG. 2C is a cross-sectional view of a zoom optical system at a telephoto according to the first embodiment of the present invention.

Tables 1 and 2 below show the optical properties of the lens included in the zoom optical system according to the first embodiment of the present invention, and Tables 3 and 4 show the Koenig constant and aspheric coefficient of the lens included in the zoom optical system according to the first embodiment of the present invention.

Here, the thickness (mm) indicates the distance from a lens surface to the next lens surface. For example, the thickness written corresponding to the object-side surface 112 of the first lens 110 indicates the distance from the object-side surface 112 of the first lens 110 to the image-side surface 114. In addition, the thickness written corresponding to the image-side surface 114 of the first lens 110 indicates the distance from the image-side surface 114 of the first lens 110 to the object-side surface 122 of the second lens 120. At the same time, the thickness written corresponding to the image-side surface 134 of the third lens 130 indicates the distance from the image-side surface 134 of the third lens 130 to the object-side surface 212 of the fourth lens 210. In this case, the fourth lens 210 is a lens included in the second lens group 200 and moves in the process of zooming from wide angle to telephoto, and therefore the thickness of the image side surface 134 written to correspond to the third lens 130 may have a value ranging from 2.877 at the shortest distance to 0.4 at the longest distance. Then, the thickness of the image side surface 134 written to correspond to the fifth lens 130 and the thickness of the image side surface 134 written to correspond to the seventh lens 130 are the same as the thickness of the image side surface 134 written to correspond to the third lens 130.

2A to 2C and Tables 1 to 4, the zoom optical system includes a first lens group 100, a second lens group 200, a third lens group 300 and a fourth lens group 400 sequentially arranged in a direction from an object side to an image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130 sequentially arranged in a direction from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220 sequentially arranged in a direction from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320 sequentially arranged in a direction from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. In this case, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, and the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134.

In addition, the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

In addition, the sixth lens 310 may include a convex object-side surface 312 and a convex image-side surface 314, and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324.

In addition, the eighth lens 410 may include a convex object-side surface 412 and a convex image-side surface 414.

The first lens 110 may have positive refractive power, the second lens 120 may have positive refractive power, and the third lens 130 may have negative refractive power. The fourth lens 210 may have positive refractive power, and the fifth lens 220 may have negative refractive power. The sixth lens 310 may have positive refractive power, and the seventh lens 320 may have negative refractive power. The eighth lens 410 may have positive refractive power.

In addition, the Abbe number of the fourth lens 210 is 49.5, which is the highest Abbe number among the Abbe numbers of the first lens 110 to the eighth lens 410. The focal length (f) of the seventh lens 320 is 1.772 mm, which is the highest refractive index among the focal lengths of the first lens 110 to the eighth lens 410. The fourth lens 210 and the seventh lens 320 can be glass lenses.

In each of the fifth lens 220, the sixth lens 310, and the seventh lens 320, the length of the long axis of the effective diameter is equal to the length of the short axis of the effective diameter. That is, when the D-cut technology is applied to the above lenses, the effective diameter may not be cut. However, in each of the first lens 110 to the fourth lens 210 and the eighth lens 410, since the length of the long axis of the effective diameter is different from the length of the short axis of the effective diameter, a part of the upper part and a part of the lower part of the effective diameter may be cut.

In FIG. 2A , in a case where the distance between the first lens group 100 and the second lens group 200 is d1a, the distance between the second lens group 200 and the third lens group 300 is d2a, and the distance between the third lens group 300 and the fourth lens group 400 is d3a, for example, the magnification may be 5 times in a wide angle. In addition, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100, as illustrated in FIG2B and FIG2C, the distance between the first lens group 100 and the second lens group 200 can be reduced to d1c, the distance between the second lens group 200 and the third lens group 300 can be reduced to d2c, and the distance between the third lens group 300 and the fourth lens group 400 can be reduced to d3c, so that, for example, the magnification can be 7.5 times in telephoto. As described above, when the second lens group 200 and the third lens group 300 are moved, the magnification of the zoom optical system can be continuously adjusted from 5 times to 7.5 times.

Therefore, in the wide angle of FIG. 2A , it can be seen that the EFL of the zoom optical system according to the first embodiment is 17.44 mm and its f-number (Fno) is 2.91, and in the telephoto of FIG. 2C , the EFL of the zoom optical system according to the first embodiment is 26.33 mm and its f-number (Fno) is 4.02.

In this case, it can be seen that the movement amount of the third lens group 300 is greater than the movement amount of the second lens group 200. That is, the difference between d1a and d1b can be smaller than the difference between d2a and d2b, and the difference between d1b and d1c can be smaller than the difference between d2b and d2c.

FIG. 3A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at wide angle for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the first embodiment, FIG. 3B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at intermediate mode for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the first embodiment, and FIG. 3C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at telephoto for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the first embodiment.

Longitudinal spherical aberration refers to the longitudinal spherical aberration according to each wavelength, the astigmatism field curve refers to the aberration properties in the tangential plane and the sagittal plane according to the height of the image surface, and the distortion refers to the degree of distortion according to the height of the image surface. Referring to Figure 3A to Figure 3C, it can be seen that the longitudinal spherical aberration is in the range of -0.05mm to 0.05mm, regardless of the wavelength, the astigmatism field curve is in the range of -0.05mm to 0.05mm, regardless of the wavelength, and the distortion is in the range of -0.05mm to 0.05mm.

FIG. 4A is a cross-sectional view of a zoom optical system at a wide angle according to the second embodiment of the present invention, FIG. 4B is a cross-sectional view of a zoom optical system at an intermediate mode according to the second embodiment of the present invention, and FIG. 4C is a cross-sectional view of a zoom optical system at a telephoto according to the second embodiment of the present invention.

Table 5 below shows the optical properties of the lens included in the zoom optical system according to the second embodiment of the present invention, and Tables 6 and 7 show the Koenig constant and aspheric coefficient of the lens included in the zoom optical system according to the second embodiment of the present invention.

Here, thickness (mm) indicates the distance from a lens surface to the next lens surface. For example, the thickness written to correspond to the object-side surface 112 of the first lens 110 indicates the distance from the object-side surface 112 of the first lens 110 to the image-side surface 114. In addition, the thickness written to correspond to the image-side surface 114 of the first lens 110 indicates the distance from the image-side surface 114 of the first lens 110 to the object-side surface 122 of the second lens 120.

4A to 4C and Tables 5 to 7, the zoom optical system includes a first lens group 100, a second lens group 200, a third lens group 300, and a fourth lens group 400 sequentially arranged in a direction from an object side to an image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130 sequentially arranged in a direction from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220 sequentially arranged in a direction from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320 sequentially arranged in a direction from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. In this case, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, and the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134.

In addition, the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

In addition, the sixth lens 310 may include a convex object-side surface 312 and a convex image-side surface 314, and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324.

In addition, the eighth lens 410 may include a convex object-side surface 412 and a convex image-side surface 414.

In FIG. 4A , in a case where the distance between the first lens group 100 and the second lens group 200 is d1a, the distance between the second lens group 200 and the third lens group 300 is d2a, and the distance between the third lens group 300 and the fourth lens group 400 is d3a, for example, the magnification may be 5 times in a wide angle. In addition, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100, as illustrated in FIG. 4B and FIG. 4C, the distance between the first lens group 100 and the second lens group 200 can be reduced to d1c, the distance between the second lens group 200 and the third lens group 300 can be reduced to d2c, and the distance between the third lens group 300 and the fourth lens group 400 can be reduced to d3c, so that, for example, the magnification can be 7.5 times in telephoto. As described above, when the second lens group 200 and the third lens group 300 are moved, the magnification of the zoom optical system can be continuously adjusted from 5 times to 7.5 times.

In this case, it can be seen that the movement amount of the third lens group 300 is greater than the movement amount of the second lens group 200. That is, the difference between d1a and d1b can be smaller than the difference between d2a and d2b, and the difference between d1b and d1c can be smaller than the difference between d2b and d2c.

FIG. 5A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at wide angle for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the second embodiment, FIG. 5B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at intermediate mode for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the second embodiment, and FIG. 5C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at telephoto for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the second embodiment.

Longitudinal spherical aberration refers to the longitudinal spherical aberration according to each wavelength, the astigmatism field curve refers to the aberration properties in the tangential plane and the sagittal plane according to the height of the image surface, and the distortion refers to the degree of distortion according to the height of the image surface. Referring to Figure 5A to Figure 5C, it can be seen that, regardless of wavelength, the longitudinal spherical aberration is in the range of -0.05mm to 0.05mm, regardless of the wavelength, the astigmatism field curve is in the range of -0.05mm to 0.05mm, regardless of the wavelength, and the distortion is in the range of -0.05mm to 0.05mm.

FIG. 6A is a cross-sectional view of a zoom optical system at a wide angle according to the third embodiment of the present invention, FIG. 6B is a cross-sectional view of a zoom optical system at an intermediate mode according to the third embodiment of the present invention, and FIG. 6C is a cross-sectional view of a zoom optical system at a telephoto according to the third embodiment of the present invention.

Table 8 below shows the optical properties of the lens included in the zoom optical system according to the third embodiment of the present invention, and Tables 9 and 10 show the Koenig constant and aspheric coefficient of the lens included in the zoom optical system according to the third embodiment of the present invention.

Here, thickness (mm) indicates the distance from a lens surface to the next lens surface. For example, the thickness written to correspond to the object-side surface 112 of the first lens 110 indicates the distance from the object-side surface 112 of the first lens 110 to the image-side surface 114. In addition, the thickness written to correspond to the image-side surface 114 of the first lens 110 indicates the distance from the image-side surface 114 of the first lens 110 to the object-side surface 122 of the second lens 120.

6A to 6C and Tables 8 to 10, the zoom optical system includes a first lens group 100, a second lens group 200, a third lens group 300 and a fourth lens group 400 sequentially arranged in a direction from an object side to an image side. The first lens group 100 includes a first lens 110, a second lens 120, and a third lens 130 sequentially arranged in a direction from the object side to the image side, the second lens group 200 includes a fourth lens 210 and a fifth lens 220 sequentially arranged in a direction from the object side to the image side, the third lens group 300 includes a sixth lens 310 and a seventh lens 320 sequentially arranged in a direction from the object side to the image side, and the fourth lens group 400 includes an eighth lens 410. In this case, the first lens 110 may include a convex object-side surface 112 and a concave image-side surface 114, the second lens 120 may include a convex object-side surface 122 and a convex image-side surface 124, and the third lens 130 may include a concave object-side surface 132 and a concave image-side surface 134.

In addition, the fourth lens 210 may include a convex object-side surface 212 and a convex image-side surface 214, and the fifth lens 220 may include a convex object-side surface 222 and a concave image-side surface 224.

In addition, the sixth lens 310 may include a convex object-side surface 312 and a convex image-side surface 314, and the seventh lens 320 may include a concave object-side surface 322 and a concave image-side surface 324.

In addition, the eighth lens 410 may include a convex object-side surface 412 and a convex image-side surface 414.

In FIG. 6A , in a case where the distance between the first lens group 100 and the second lens group 200 is d1a, the distance between the second lens group 200 and the third lens group 300 is d2a, and the distance between the third lens group 300 and the fourth lens group 400 is d3a, for example, the magnification may be 5 times in a wide angle. In addition, when the second lens group 200 and the third lens group 300 are moved closer to the first lens group 100, as illustrated in FIG6B and FIG6C, the distance between the first lens group 100 and the second lens group 200 can be reduced to d1c, the distance between the second lens group 200 and the third lens group 300 can be reduced to d2c, and the distance between the third lens group 300 and the fourth lens group 400 can be reduced to d3c, so that, for example, the magnification can be 7.5 times in telephoto. As described above, when the second lens group 200 and the third lens group 300 are moved, the magnification of the zoom optical system can be continuously adjusted from 5 times to 7.5 times.

In this case, it can be seen that the movement amount of the third lens group 300 is greater than the movement amount of the second lens group 200. That is, the difference between d1a and d1b can be smaller than the difference between d2a and d2b, and the difference between d1b and d1c can be smaller than the difference between d2b and d2c.

FIG. 7A is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at wide angle for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the third embodiment, FIG. 7B is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at intermediate mode for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the third embodiment, and FIG. 7C is a diagram showing longitudinal spherical aberration, astigmatism field curve and distortion in an optical system at telephoto for light of wavelengths of 435nm, 486nm, 546nm, 587nm and 656nm according to the third embodiment.

Longitudinal spherical aberration refers to the longitudinal spherical aberration according to each wavelength, the astigmatism field curve refers to the aberration properties in the tangential plane and the sagittal plane according to the height of the image surface, and the distortion refers to the degree of distortion according to the height of the image surface. Referring to Figures 7A to 7C, it can be seen that the longitudinal spherical aberration is in the range of -0.05mm to 0.05mm regardless of the wavelength, the astigmatism field curve is in the range of -0.05mm to 0.05mm, and is independent of the wavelength, and the distortion is in the range of -0.05mm to 0.05mm.

As described above with reference to the embodiments, it can be seen that the optical system according to the embodiments of the present invention has high aberration properties.

Meanwhile, the zoom optical system according to an embodiment of the present invention can be applied to a camera module. A camera module including the zoom optical system according to an embodiment of the present invention can be installed in a portable terminal and applied to the portable terminal together with a main camera module. The camera module according to an embodiment of the present invention can include an image sensor, a filter disposed on the image sensor, and a zoom optical system disposed on the filter, and the zoom optical system according to an embodiment of the present invention can include the first lens group 100, the second lens group 200, the third lens group 300, and the fourth lens group 400 described above. The portable terminal in which the camera module including the zoom optical system according to the embodiment of the present invention is installed may be a smart phone, a tablet personal computer (PC), a laptop computer, a personal digital assistant (PDA), etc.

At the same time, the optical system according to an embodiment of the present invention can be applied to a camera module. FIG8 is a view illustrating a portion of a portable terminal, in which a camera module according to an embodiment of the present invention is applied.

Referring to FIG. 8 , a camera module including a zoom optical system 1000 according to an embodiment of the present invention can be installed in a portable terminal and can be applied to the portable terminal together with a main camera module 1100.

The zoom optical system 1000 according to the embodiment of the present invention may include the first lens group 100, the second lens group 200, the third lens group 300 and the fourth lens group 400 described above, and the first lens group 100, the second lens group 200, the third lens group 300 and the fourth lens group 400 may be sequentially arranged in the lateral direction of the portable terminal due to the thickness limitation of the portable terminal. For this purpose, as described above, a right angle prism may be further arranged in front of the first lens group 100. When the zoom optical system is arranged in the thickness direction of the portable terminal, that is, the lens surface of the lens included in the zoom optical system is arranged in the thickness direction of the portable terminal, the diameter of the lens included in the zoom optical system can be reduced to reduce the thickness of the portable terminal. Therefore, the zoom optical system that allows the magnification to be continuously adjusted by moving the lens can also be installed in the portable terminal.

The portable terminal in which the camera module including the zoom optical system according to the embodiment of the present invention is installed may be a smart phone, a tablet PC, a laptop computer, a PDA, etc.

FIG. 9 is a view of a camera module including a zoom optical system according to an embodiment of the present invention.

Referring to FIG. 9 , the camera module 2000 including the zoom optical system according to the embodiment of the present invention may be implemented to have a hexahedral shape. The width w of the camera module 2000 may be greater than 13.10 mm and less than 14.50 mm. The width w of the camera module 2000 may be 13.80 mm. The length l of the camera module 2000 may be greater than 27.00 mm and less than 30.00 mm. The length l of the camera module 2000 may be 28.5 mm. The height h of the camera module 2000 may be greater than 5.80 mm and less than 6.60 mm. The height h of the camera module 2000 may be 6.2 mm.

The camera module 2000 including the zoom optical system according to an embodiment of the present invention may include an image sensor. The size of the image sensor may be greater than 0.30 inches and less than 0.34 inches. According to an embodiment, the size of the image sensor may be 1/3.14 inches.

The camera module 2000 including the zoom optical system according to the embodiment of the present invention may include an actuator. The actuator may be coupled to the zoom optical system to move at least one lens group included in the zoom optical system. In addition, the actuator may be coupled to the zoom optical system to move the prism. The actuator may include at least one of a pin component and a spherical component.

In addition, the camera module 2000 including the zoom optical system according to the embodiment of the present invention may include a driver integrated circuit (IC), a printed circuit board, etc.

The camera module 2000 including the zoom optical system according to an embodiment of the present invention may have a first field of view (FOV) in wide angle and a second FoV in telephoto. The first FoV may have a value greater than 17.70° and less than 19.70°. The first FoV may be 18.7°. The second FoV may have a value greater than 11.80° and less than 13.20°. The first FoV may be 12.5°.

The camera module 2000 including the zoom optical system according to an embodiment of the present invention may have a first f-number in wide angle and a second f-number in telephoto. The first f-number may have a value greater than 2.80 and less than 3.20. The first f-number may be 3.0. The second f-number may have a value greater than 4.20 and less than 4.80. The second f-number may be 4.5.

Although the present invention is described above mainly with reference to the embodiments, those skilled in the art should understand that the present invention is not limited to the embodiments, but such embodiments are merely illustrative, and various modifications and applications not described above can be made within the scope of the present invention without departing from the essential features of the embodiments of the present invention. For example, the components specifically described in the embodiments can be modified and implemented. In addition, it should be understood that the differences related to the modifications and applications belong to the scope of the present invention as defined by the scope of the attached patent application.

10: Image sensor

20: Filter

100: First lens group

200: Second lens group

300: Third lens group

400: The fourth lens group

Claims (12)

A zoom optical system comprises a first lens group, a second lens group, a third lens group and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, a total track length (TTL) is less than 20 mm, and an effective focal length (EFL) in a telephoto is greater than 25 mm; wherein the zoom optical system further comprises a right angle prism arranged in sequence in front of the first lens group in the direction from the object side to the image side. A zoom optical system as claimed in claim 1, wherein the EFL in the telephoto is greater than 1.5 times the EFL in the wide-angle. A zoom optical system as claimed in claim 1, wherein a movement stroke of the second lens group is less than 2.5 mm during zooming from a wide angle to the telephoto. A zoom optical system as claimed in claim 1, wherein the second lens group and the third lens group include at least one glass lens. A zoom optical system as claimed in claim 4, wherein the glass lens has: a refractive index greater than 1.7; or an Abbe number greater than 60. A zoom optical system as claimed in claim 1, wherein the lenses included in the first lens group to the fourth lens group include D-cut lenses. A zoom optical system as claimed in claim 6, wherein the second lens group and the third lens group include lenses in which a value of 1 is obtained by dividing a length of a major axis of an effective diameter by a length of a minor axis of the effective diameter. A zoom optical system as claimed in claim 1, wherein a chief ray angle (CRA) is less than 6°. A zoom optical system as claimed in claim 1, wherein a value obtained by dividing the EFL by an f-number is greater than 6 at the telephoto. A zoom optical system as claimed in claim 1, wherein, in the telephoto: the EFL is greater than 25 mm; and an f-number is less than 4.2. A zoom optical system includes a first lens group, a second lens group, a third lens group and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, and in a telephoto, an effective focal length (EFL) is greater than 25 mm, and an f-number is less than 4.2. A zoom optical system includes a first lens group, a second lens group, a third lens group, and a fourth lens group arranged in sequence in a direction from an object side to an image side, wherein the second lens group and the third lens group are movable, and a value obtained by dividing an effective focal length (EFL) by an f-number is greater than 6 in a telephoto.

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