CN115437119A - Optical imaging system - Google Patents

Abstract

The optical imaging system includes a first lens group, a second lens group, a third lens group, and a fourth lens group that are sequentially disposed from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system, wherein at least one lens group among the first lens group to the fourth lens group is configured to be movable along the optical axis, the first lens group has a positive refractive power, and includes a reflective member and at least one lens disposed between the object side of the optical imaging system and the second lens group, and the at least one lens is configured to refract light passing through the at least one lens to be incident on the reflective member with the light being condensed.

Description

Optical imaging system

Cross Reference to Related Applications

This application claims the benefit of priority of korean patent application No. 10-2021-0190122, filed in korean intellectual property office at 28.12.2021, the entire disclosure of which is incorporated herein by reference for all purposes.

Technical Field

The present application relates to optical imaging systems.

Background

Recently, camera modules have become an essential feature in mobile electronic devices including smart phones.

Further, a method of mounting a plurality of camera modules having different focal lengths in a mobile electronic device in order to indirectly achieve an optical zoom effect has recently been proposed.

However, this method requires not only a plurality of camera modules for optical zoom effect, but also imaging processing by software instead of optical zoom when capturing an image at an intermediate magnification due to a difference in field of view between the plurality of camera modules, and thus image quality deteriorates.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one general aspect, an optical imaging system includes a first lens group, a second lens group, a third lens group, and a fourth lens group disposed in order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system, wherein at least one lens group among the first lens group to the fourth lens group is configured to be movable along the optical axis, the first lens group has a positive refractive power, and includes a reflective member and at least one lens disposed between the object side of the optical imaging system and the second lens group, and the at least one lens is configured to refract light passing through the at least one lens to be incident on the reflective member with the condensed light.

At least one lens of the first lens group may include a first lens and a second lens disposed in order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis, the first lens may be disposed between the object side of the optical imaging system and the reflective member, and the second lens may be disposed between the object side of the optical imaging system and the reflective member or between the reflective member and the second lens group.

An abbe number of one of the first lens and the second lens may be 50 or more, and an abbe number of the other of the first lens and the second lens may be 40 or less.

One of the first lens and the second lens may have a positive refractive power, and the other of the first lens and the second lens may have a negative refractive power, and an abbe number of a lens having a positive refractive power among the first lens and the second lens may be 50 or more, and an abbe number of a lens having a negative refractive power among the first lens and the second lens may be 40 or less.

The second lens group may have a negative refractive power, and may be configured to be movable away from an object side of the optical imaging system toward an imaging surface of the optical imaging system to narrow a field of view of the optical imaging system, and movable away from the imaging surface of the optical imaging system toward the object side of the optical imaging system to enlarge the field of view of the optical imaging system.

The second lens group may include a plurality of lenses having a negative compound refractive power, and any one of the plurality of lenses of the second lens group may have a concave object-side surface and a concave image-side surface.

In the optical imaging system, 0.6 ≦ fGc/fG2 ≦ 0.9 may be satisfied, where fGc is a focal length of a lens having a concave object-side surface and a concave image-side surface, and fG2 is a focal length of the second lens group.

The first lens group and the third lens group may be disposed at fixed positions on the optical axis, and the fourth lens group may be configured to be movable toward the object side of the optical imaging system away from the imaging surface of the optical imaging system to correct a focal position of the optical imaging system when the second lens group is moved away from the object side of the optical imaging system toward the imaging surface of the optical imaging system to narrow the field of view of the optical imaging system, and to be movable toward the imaging surface of the optical imaging system away from the object side of the optical imaging system to correct the focal position of the optical imaging system when the second lens group is moved toward the object side of the optical imaging system to enlarge the field of view of the optical imaging system.

In the optical imaging system, 1.8 ≦ kf/kr ≦ -1.2, where kf is a refractive power of a first surface of the fourth lens group closest to the object side of the optical imaging system, and kr is a refractive power of a last surface of the fourth lens group closest to an imaging surface of the optical imaging system.

The fourth lens group may be further configured to be movable away from an imaging surface of the optical imaging system toward the object side of the optical imaging system when the object distance changes from infinity to a close distance, and may satisfy 0 ≦ Laf/fG4 ≦ 0.1, where Laf is an amount of movement of the fourth lens group at a telephoto end of the optical imaging system where a field of view of the optical imaging system is narrowest, and fG4 is a focal length of the fourth lens group when the object distance changes from infinity to the close distance.

The third lens group and the fourth lens group may each have positive refractive power.

The third lens group may include a stop and a plurality of lenses disposed in order away from the object side of the optical imaging system toward the imaging surface of the optical imaging system along the optical axis, and a lens disposed closest to the stop among the plurality of lenses of the third lens group may have a positive refractive power.

The object side or image side of the lens disposed closest to the stop may be aspherical.

The first surface of the first lens group is a surface of the first lens group disposed on the object side of the optical imaging system, and may satisfy 0.4 ≦ D13/TTL ≦ 0.6, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and TTL is an optical axis distance from the first surface of the first lens group to the imaging surface.

The first surface of the first lens group is a surface of the first lens group disposed on the object side of the optical imaging system, and may satisfy 0.4 ≦ D13/fG1 ≦ 0.8, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and fG1 is a focal length of the first lens group.

In the optical imaging system, 0.4 ≦ fG12w/fG12t ≦ 0.7 may be satisfied, where fG12w is a composite focal length of the first lens group and the second lens group at the wide-angle end of the optical imaging system where the field of view of the optical imaging system is widest, and fG12t is a composite focal length of the first lens group and the second lens group at the telephoto end of the optical imaging system where the field of view of the optical imaging system is narrowest.

In another general aspect, an optical imaging system includes a first lens group, a second lens group, a third lens group, and a fourth lens group disposed in order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system, one of the first to fourth lens groups being configured to be movable along the optical axis to change a focal length of the optical imaging system, another one of the first to fourth lens groups being configured to be movable along the optical axis to correct a focal position of the optical imaging system, and the first lens group includes a reflecting member configured to change a path of light incident on the reflecting member, and at least one lens configured to condense light entering the optical imaging system onto the reflecting member.

The first lens group and the third lens group may be disposed at fixed positions on the optical axis, the second lens group may be configured to be movable along the optical axis to change a focal length of the optical imaging system, and the fourth lens group may be configured to be movable along the optical axis to correct a focal position of the optical imaging system when the second lens group is moved along the optical axis to change the focal length of the optical imaging system.

The second lens group and the fourth lens group may be further configured such that when the second lens group is moved along the optical axis to change the focal length of the optical imaging system, the second lens group and the fourth lens group are moved in opposite directions relative to each other along the optical axis, and when the second lens group is moved along the optical axis to change the focal length of the optical imaging system, the fourth lens group is moved along the optical axis to correct a focal position of the optical imaging system.

The other of the first to fourth lens groups may be further configured to be movable along the optical axis when the object distance is changed between an infinite distance and a close distance.

Other features and aspects will become apparent from the following claims, the accompanying drawings, and the following detailed description.

Drawings

Fig. 1 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a first example of an optical imaging system when an object distance is infinite.

Fig. 2 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a first example of the optical imaging system when the object distance is a short distance (600 mm).

Fig. 3 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a second example of the optical imaging system when the object distance is infinite.

Fig. 4 is an expanded view showing the wide-angle end, the standard end, and the telephoto end of the second example of the optical imaging system when the object distance is a short distance (600 mm).

Fig. 5 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a third example of the optical imaging system when the object distance is infinite.

Fig. 6 is a development view showing a wide-angle end, a standard end, and a telephoto end of a third example of the optical imaging system when the object distance is a close distance (600 mm).

Like reference numerals refer to like elements throughout the drawings and detailed description. The figures may not be drawn to scale and the relative sizes, proportions and depictions of the elements in the figures may be exaggerated for clarity, illustration and convenience.

Detailed Description

The following detailed description is provided to assist the reader in obtaining a thorough understanding of the methods, apparatuses, and/or systems described herein. Various changes, modifications, and equivalents of the methods, devices, and/or systems described herein will, however, become apparent after understanding the disclosure of this application. For example, the order of operations described herein is merely an example, and is not limited to the order set forth herein, except as operations that must occur in a particular order, but may be varied as will be apparent upon understanding the disclosure of the present application. In addition, descriptions of features well known in the art may be omitted for greater clarity and conciseness.

The features described herein may be embodied in different forms and should not be construed as limited to the examples described herein. Rather, the examples described herein are provided merely to illustrate some of the many possible ways to implement the methods, apparatuses, and/or systems described herein that will be apparent after understanding the disclosure of the present application.

In this document, use of the word "may" in describing various examples, such as in relation to what an example may include or implement, means that there is at least one example in which such a feature is included or implemented, but not all examples are limited to such.

Throughout the specification, when an element such as a layer, region or substrate is described as being "on," "connected to" or "coupled to" another element, it can be directly on, connected to or coupled to the other element or one or more other elements may be present between the element and the other element. In contrast, when an element is referred to as being "directly on," "directly connected to" or "directly coupled to" another element, there are no other elements intervening between the element and the other element.

As used herein, the term "and/or" includes any one of the associated listed items as well as any combination of any two or more of the items.

Although terms such as "first", "second", and "third" may be used herein to describe various elements, components, regions, layers or sections, these elements, components, regions, layers or sections are not limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first member, first component, first region, first layer, or first portion referred to in these examples may also be referred to as a second member, second component, second region, second layer, or second portion without departing from the teachings of the examples described herein.

Spatially relative terms such as "over 8230; \8230; above", "under 8230; \8230; and" below "may be used herein for ease of description to describe the relationship of one element to another as shown in the figures. These spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "above" or "upper" relative to other elements would then be oriented "below" or "lower" relative to the other elements. Thus, the phrase "over" encompasses both orientations of "over" and "under", depending on the spatial orientation of the device, 8230 \8230 @. The device may also be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative terms used herein should be interpreted accordingly.

The terminology used herein is for the purpose of describing various examples only and is not intended to be limiting of the disclosure. The articles "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" specify the presence of stated features, integers, operations, elements, and/or groups thereof, but do not preclude the presence or addition of one or more other features, integers, operations, elements, components, and/or groups thereof.

Variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, may be expected. Thus, examples described herein are not limited to the specific shapes shown in the drawings, but include changes in shape that occur during manufacture.

The features of the examples described herein may be combined in various ways that will be apparent after understanding the disclosure of this application. Further, while the examples described herein have a variety of configurations, other configurations are possible as will be apparent after understanding the disclosure of this application.

In the drawings, the thickness, size, and shape of the lens may be slightly exaggerated for convenience of explanation. In particular, the shapes of the spherical surface or the aspherical surface shown in the drawings are shown by way of example. That is, the shapes of the spherical surface or the aspherical surface are not limited to those shown in the drawings.

Examples of the optical imaging system described in the present application may be installed in a mobile electronic device. For example, the optical imaging system may be a component of a camera module installed in the mobile electronic device. The mobile electronic device may be a portable electronic device such as a mobile communication terminal, a smart phone, or a tablet personal computer.

In the examples described herein, the first lens (or the frontmost lens) refers to a lens closest to the object side of the optical imaging system, and the last lens (or the last lens) refers to a lens closest to the imaging plane (or the image sensor) of the optical imaging system.

Further, the first surface of each lens means a surface thereof close to the object side of the optical imaging system (or an object side surface), and the second surface of each lens means a surface thereof close to the imaging surface of the optical imaging system (or an image side surface).

The values of the radius of curvature, thickness, distance and focus are expressed in millimeters (mm), the value of the field of view (FOV) is expressed in degrees, and the values of the F-number (Fno) and Magnification (MAG) are dimensionless quantities.

The radius of curvature of the lens surface is measured at the optical axis. The thicknesses of the lens and other optical elements and the distances between the lens and other optical elements are measured along the optical axis of the optical imaging system.

Unless otherwise specified, the shape of a lens surface refers to the shape of the paraxial region of the lens surface. The paraxial region of the lens surface, in which light rays incident on the lens surface form a small angle θ with the optical axis, is the central portion of the lens surface around and including the optical axis of the lens surface, and approximations of sin θ ≈ θ, tan θ ≈ θ, and cos θ ≈ 1 are effective.

For example, the expression that the object side of the lens is convex means that at least the paraxial region of the object side of the lens is convex, and the expression that the image side of the lens is concave means that at least the paraxial region of the image side of the lens is concave. Thus, even though the object side surface of the lens may be described as convex, the entire object side surface of the lens may not be convex, and the peripheral region of the object side surface of the lens may be concave. Further, even though the image side surface of the lens may be described as concave, the entire image side surface of the lens may not be concave, and the peripheral region of the image side surface of the lens may be convex.

An imaging plane may refer to a virtual surface on which an image of an object is focused by an optical imaging system. Alternatively, the imaging plane may refer to one surface of the image sensor on which light is received.

An example of an optical imaging system may include a plurality of lens groups. As an example, the optical imaging system may include a first lens group, a second lens group, a third lens group, and a fourth lens group.

At least some of the first to fourth lens groups may include a plurality of lenses. As an example, the optical imaging system may comprise at least seven lenses.

In one example, the optical imaging system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and an eighth lens that are disposed in this order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system.

In another example, the optical imaging system may include a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens that are disposed in this order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system.

The optical imaging system may further include a reflecting member having a reflecting surface that changes an optical path. As an example, the reflecting member may be a mirror or a prism.

By bending the optical path with the reflecting member, a long optical path can be formed in a relatively narrow space.

Therefore, the optical imaging system can be miniaturized and can have a long focal length.

In addition, the optical imaging system may further include an image sensor that converts an image of an object incident on the image sensor into an electrical signal.

Further, the optical imaging system may further include an infrared cut filter (hereinafter referred to as a filter) that cuts infrared light. A filter may be disposed between the last lens and the image sensor.

Further, the optical imaging system may further include a stop disposed between the second lens group and the third lens group. In one example, the stop may be disposed between the fifth lens and the sixth lens. In another example, a stop may be disposed between the fourth lens and the fifth lens.

In one example, the first lens group may include a first lens, a second lens, and a reflective member, the second lens group may include a third lens, a fourth lens, and a fifth lens, the third lens group may include a sixth lens and a seventh lens, and the fourth lens group may include an eighth lens. That is, the reflective member may be disposed between the second lens and the third lens. The third lens group may further include a stop disposed in front of the sixth lens.

In another example, the first lens group may include a first lens, a reflective member, and a second lens, the second lens group may include a third lens and a fourth lens, the third lens group may include a fifth lens and a sixth lens, and the fourth lens group may include a seventh lens. That is, the reflective member may be disposed between the first lens and the second lens. The third lens group may further include a stop disposed in front of the fifth lens.

In another example, the first lens group may include a first lens, a second lens, and a reflective member, the second lens group may include a third lens and a fourth lens, the third lens group may include a fifth lens and a sixth lens, and the fourth lens group may include a seventh lens. That is, the reflective member may be disposed between the second lens and the third lens. The third lens group may further include a stop disposed in front of the fifth lens.

Some of the multiple lenses may be bonded to each other to form one or more bonded lenses. In one example, the first and second lenses may be bonded to each other to form a bonded lens, and the fourth and fifth lenses may be bonded to each other to form another bonded lens. In another example, the first lens and the second lens may be bonded to each other to form a bonded lens.

At least some of the plurality of lenses may be spaced apart from each other at predetermined intervals along the optical axis.

At least one lens group among the first to fourth lens groups may be configured to be movable so as to change an overall focal length of the optical imaging system.

For example, the interval between the first lens group and the second lens group may be changed so as to change the overall focal length of the optical imaging system. As an example, the first lens group may be disposed at a fixed position, and the second lens group may be configured to be movable in the optical axis direction. When the second lens group moves away from the object side toward the imaging surface, the total focal length of the optical imaging system may be changed from the wide-angle end to the telephoto end.

Since the first lens group is located at the forefront in the optical imaging system, when the first lens group is disposed at a fixed position, a waterproof and dustproof optical imaging system can be easily realized.

The first lens group may include a reflective member and at least one lens disposed in front of the reflective member and having a meniscus shape whose object side surface is convex, and the first lens group as a whole may have a positive refractive power. Further, light passing through at least one lens disposed in front of the reflecting member may be refracted to be condensed and incident on the reflecting member.

In one example, the first lens group may include a reflective member and two lenses (e.g., a first lens and a second lens).

At least one of the two lenses may be disposed in front of the reflecting member. That is, both the first lens and the second lens may be disposed in front of the reflective member, or the first lens may be disposed in front of the reflective member and the second lens may be disposed behind the reflective member.

Each of the first lens and the second lens may have a meniscus shape whose object side is convex.

When both the first lens and the second lens are disposed in front of the reflection member, a composite focal length of the first lens and the second lens may have a positive value.

When the first lens is disposed in front of the reflection member, a focal length of the first lens may have a positive value, and a focal length of the second lens may have a negative value.

Further, the first lens and the second lens may be made of materials having different optical characteristics. For example, the first lens may be made of a material having a high dispersion value, and the second lens may be made of a material having a low dispersion value. Therefore, the chromatic aberration correction capability of the optical imaging system can be improved.

In one example, an abbe number of one of the first lens and the second lens may be 50 or more, and an abbe number of the other of the first lens and the second lens may be 40 or less.

In one example, an abbe number of a lens having a positive refractive power among the first lens and the second lens may be 50 or more, and an abbe number of a lens having a negative refractive power among the first lens and the second lens may be 40 or less.

In one example, an average of the refractive index of the first lens and the refractive index of the second lens may exceed 1.7.

The second lens group may include a plurality of lenses, and may have a negative refractive power as a whole.

In one example, the second lens group may include a third lens, a fourth lens, and a fifth lens. Any one of the third lens to the fifth lens may have a shape in which both surfaces are concave.

For example, the third lens may have a meniscus shape whose object side is convex, and may have a negative refractive power. The fourth lens may have a shape in which both surfaces thereof are concave, and may have a negative refractive power. The fifth lens may have a meniscus shape whose object side surface is convex, and may have a positive refractive power.

In another example, the second lens group may include a third lens and a fourth lens. Either one of the third lens and the fourth lens may have a shape in which both surfaces are concave.

For example, the third lens may have a concave shape in which both surfaces thereof are concave, and may have a negative refractive power. The fourth lens may have a meniscus shape whose object side is convex, and may have a positive refractive power.

The third lens group may include a stop and a plurality of lenses, and may have a positive refractive power as a whole.

A lens disposed closest to the stop (e.g., a lens located directly behind the stop) among the plurality of lenses included in the third lens group may have a positive refractive power.

The composite focal length of the first lens group and the second lens group may have a negative value. This makes the light passing through the first lens group and the second lens group diverge, so that the diameter of the lens disposed behind the lens disposed closest to the stop can be reduced by making the lens disposed closest to the stop, among the plurality of lenses included in the third lens group, have positive refractive power.

Further, a lens disposed closest to the diaphragm (e.g., a lens located directly behind the diaphragm) may have an aspheric surface.

In one example, the third lens group may include a stop, a sixth lens, and a seventh lens.

The sixth lens may have a shape in which both surfaces thereof are convex, and may have a positive refractive power. The seventh lens may have a meniscus shape whose object side is convex, and may have a negative refractive power.

In another example, the third lens group may include a stop, a fifth lens, and a sixth lens.

The fifth lens may have a shape in which both surfaces thereof are convex, and may have a positive refractive power. The sixth lens may have a meniscus shape whose object side is convex, and may have a negative refractive power.

The stop included in the third lens group may be an variable stop having a variable diameter. In this case, it is necessary to apply electric power to change the diameter of the stop, and thus the third lens group can be disposed at a fixed position.

The fourth lens group may include at least one lens, and may have a positive refractive power as a whole.

In one example, the fourth lens group may include an eighth lens, and the eighth lens may have a meniscus shape whose object side surface is convex, and may have a positive refractive power.

In another example, the fourth lens group may include a seventh lens, and the seventh lens may have a meniscus shape whose object side surface is convex, and may have a positive refractive power.

At least one lens group among the first to fourth lens groups may be configured to be movable so as to correct a focal position according to a change in a total focal length of the optical imaging system.

For example, the fourth lens group may be configured to be movable in the optical axis direction. When the fourth lens group moves, an interval between the third lens group and the fourth lens group and an interval between the fourth lens group and the image sensor change.

When the total focal length of the optical imaging system is changed from the wide-angle end to the telephoto end, the fourth lens group may be moved away from the imaging surface toward the object side to correct a focal position.

Further, when the object distance is changed from infinity to a close distance (e.g., 600 mm), the fourth lens group may be moved away from the imaging plane toward the object side.

The second lens group is movable along the optical axis to change an overall focal length of the optical imaging system (optical zoom function), and the fourth lens group is movable along the optical axis to correct a focal position with a change in the overall focal length of the optical imaging system.

Thus, an example of the optical imaging system may have an optical zoom function.

Further, an example of an optical imaging system may feature a telephoto lens having a relatively narrow field of view and a long focal length.

At least one of the plurality of lenses may have an aspherical surface. For example, the lens disposed closest to the diaphragm may have an aspherical surface.

In one example, the third lens group may include a stop. Further, at least one of an object side surface and an image side surface of a lens disposed closest to the stop among the plurality of lenses included in the third lens group may be aspherical.

The lens disposed closest to the diaphragm has a large influence on the optical characteristics (e.g., aberration correction) of the optical imaging system, and thus can be configured to have an aspherical surface.

The aspherical surface of the lens may be represented by the following equation 1:

in equation 1, C is a curvature of the lens surface and is equal to an inverse of a curvature radius of the lens surface at an optical axis of the lens surface, K is a conic constant, Y is a distance from any point on the lens surface to the optical axis of the lens surface in a direction perpendicular to the optical axis of the lens surface, a, B, C, and D are aspheric constants, and Z (or sag) is a distance from a point on the lens surface at a distance Y from the optical axis of the lens surface to a tangential plane perpendicular to the optical axis and intersecting a vertex of the lens surface in a direction parallel to the optical axis of the lens surface.

An example of the optical imaging system may satisfy any one of the following conditional expressions 1 to 6 or any combination of any two or more.

D13/TTL is more than or equal to 0.4 and less than or equal to 0.6 (conditional expression 1)

0.4. Ltoreq. D13/fG 1. Ltoreq.0.8 (conditional expression 2)

fGc/fG2 of 0.6. Ltoreq.0.9 (conditional expression 3)

Kf/kr is not less than-1.8 and not more than-1.2 (conditional expression 4)

fG12w/fG12t 0.4. Ltoreq.0.7 (conditional expression 5)

Less than or equal to 0 | Laf/fG4| less than or equal to 0.1 (conditional expression 6)

In one example of the optical imaging system, 0.4 ≦ D13/TTL ≦ 0.6 may be satisfied, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and TTL is an optical axis distance from the first surface of the first lens group to the imaging surface.

The diameter of the stop may decrease as the stop is farther from the first lens group. Therefore, moving the stop farther from the first lens group can contribute to reducing the thickness of the optical imaging system (or the thickness of a mobile electronic device in which the optical imaging system is disposed (here, the thickness is the thickness of the optical imaging system in a direction perpendicular to the optical axis direction)). However, when the stop becomes too far from the first lens group, there may be a problem that the total length (e.g., TTL) of the optical imaging system becomes long.

Further, when the stop is positioned too close to the first lens group, the diameter of the stop may increase. When the diameter of the diaphragm is increased, the opening of the diaphragm may have a non-circular shape due to a thickness limitation of the optical imaging system, so that Fno may become large and thus the amount of light may decrease, resulting in a dark photographed image. Fno is the F-number of the optical imaging system.

Therefore, 0.4 ≦ D13/TTL ≦ 0.6 may be satisfied, so that the optical imaging system may have appropriate Fno, thickness, and total length.

In another example of the optical imaging system, 0.4 ≦ D13/fG1 ≦ 0.8 may be satisfied, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and fG1 is a focal length of the first lens group.

The condition indicates a relationship between the focal length of the first lens group and the stop position. Since the first lens group has positive refractive power, light passing through the first lens group can be refracted to be condensed, and a stop needs to be provided at an appropriate position according to the degree of condensation of the light. Therefore, 0.4 ≦ D13/fG1 ≦ 0.8 may be satisfied, so that the first lens group may have an appropriate refractive power, and the optical imaging system may have an appropriate Fno, thickness, and total length.

In another example of the optical imaging system, 0.6 ≦ fGc/fG2 ≦ 0.9 may be satisfied, where fGc is a focal length of a lens whose both surfaces are convex, among lenses included in the second lens group, and fG2 is a focal length of the second lens group.

Since the second lens group is used to change the field of view of the optical imaging system (or change the total focal length of the optical imaging system), aberration variation due to the movement of the second lens group needs to be significantly reduced. The second lens group may include lenses of which both surfaces are concave, and the lenses of which both surfaces are concave may have a great influence on the optical characteristics of the optical imaging system. Therefore, 0.6 ≦ fGc/fG2 ≦ 0.9 may be satisfied, so that the second lens group may have an appropriate refractive power for changing the field of view of the optical imaging system (or changing the total focal length of the optical imaging system), and aberration variation due to movement of the second lens group may be significantly reduced.

In another example of the optical imaging system, 1.8 ≦ kf/kr ≦ -1.2 may be satisfied, where kf is a refractive power of the first surface of the fourth lens group, and kr is a refractive power of the last surface of the fourth lens group. The optical power k of each surface may be defined as k = c (n '-n), where c is the curvature of the surface (i.e., the inverse of the radius of curvature of the surface), n' is the refractive index of the medium behind the surface, and n is the refractive index of the medium in front of the surface.

Since the fourth lens group is disposed closest to the imaging surface, the fourth lens group needs to function as a field flattener (i.e., to effectively suppress an imaging surface curvature phenomenon in which an outer portion of the field of view is blurred or curved into a curved surface when the outer portion is focused on a plane), and may have a meniscus shape exhibiting weak refractive power. Therefore, kf/kr ≦ 1.2 of-1.8 may be satisfied, so that the fourth lens group may have an appropriate refractive power to effectively correct the curvature of the imaging surface.

In another example of the optical imaging system, 0.4 ≦ fG12w/fG12t ≦ 0.7 may be satisfied, where fG12w is a composite focal length of the first lens group and the second lens group at the wide-angle end, and fG12t is a composite focal length of the first lens group and the second lens group at the telephoto end.

The condition may be a condition for determining a zoom magnification, and in an example of the optical imaging system, a field of view of the optical imaging system may change due to movement of the second lens group. Therefore, 0.4. Ltoreq. FG12w/fG12 t. Ltoreq.0.7 can be satisfied, so that the optical imaging system can have an appropriate zoom magnification and the aberration correction capability can be improved.

In another example of the optical imaging system, 0 ≦ Laf/fG4 ≦ 0.1 may be satisfied, where Laf is an amount of movement of the fourth lens group at the telephoto end when the object distance is changed from infinite to a near distance (e.g., 600 mm), and fG4 is a focal length of the fourth lens group.

Since the fourth lens group is disposed closest to the imaging surface, the fourth lens group needs to function as a field flattener as described above. Therefore, 0 ≦ Laf/fG4| ≦ 0.1 may be satisfied, so that the curvature of the imaging surface may be effectively corrected.

Fig. 1 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a first example of an optical imaging system when an object distance is infinite, and fig. 2 is an expanded view showing a wide-angle end, a standard end, and a telephoto end of a first example of an optical imaging system when an object distance is a close distance (600 mm).

Referring to fig. 1 and 2, a first example of an optical imaging system may include a first lens group G11, a second lens group G12, a third lens group G13, and a fourth lens group G14.

The first lens group G11 may include, in order from the object side, a first lens 110, a second lens 120, and a reflective member R, the second lens group G12 may include a third lens 130, a fourth lens 140, and a fifth lens 150, the third lens group G13 may include a stop S, a sixth lens 160, and a seventh lens 170, and the fourth lens group G14 may include an eighth lens 180.

In addition, the optical imaging system may further include an optical filter 190 and an image sensor IS.

The optical imaging system may focus the image on an imaging plane 191. Imaging plane 191 may refer to a surface on which an image is focused by an optical imaging system. As an example, the imaging plane 191 may refer to one surface of the image sensor IS on which light IS received.

The reflecting member R may be a prism, but may alternatively be a mirror.

At least one of the first lens group G11 to the fourth lens group G14 may be moved so as to change the total focal length of the optical imaging system. As an example, the first lens group G11 and the third lens group G13 are fixed, and the second lens group G12 moves along the optical axis to change the total focal length of the optical imaging system. That is, when the second lens group G12 is moved from the object side toward the image side, the total focal length of the optical imaging system may be changed from the wide-angle end to the telephoto end.

Further, at least one of the first lens group G11 to the fourth lens group G14 may be moved so as to correct a focal position according to a variation in the total focal length of the optical imaging system. As an example, when the total focal length of the optical imaging system is changed from the wide-angle end to the telephoto end, the fourth lens group G14 may be moved from the image side toward the object side to correct the focal position.

Further, when the object distance changes from infinity to a close distance (for example, 600 mm), the fourth lens group G14 may move from the image side toward the object side.

Optical characteristics (radius of curvature, thickness of lens or distance between lenses, refractive index, abbe number, and focal length) of each element in the first example are listed in table 1 below.

TABLE 1

Table 2 below lists various other optical characteristics in the first example.

TABLE 2

In table 2, D0 is an object distance, D1 is an optical axis distance between the reflecting member R and the third lens 130, D2 is an optical axis distance between the fifth lens 150 and the stop S, D3 is an optical axis distance between the seventh lens 170 and the eighth lens 180, and D4 is an optical axis distance between the eighth lens 180 and the filter 190.

F is the total focal length of the optical imaging system, MAG is the magnification of the optical imaging system, FOV is the field of view of the optical imaging system, fno is the F-number of the optical imaging system, and TTL is the optical axis distance from the object side surface of the first lens 110 to the imaging plane 191.

A focal length fG1 of the first lens group G11 may be 26.9778mm, a focal length fG2 of the second lens group G12 may be-7.37 mm, a focal length fG3 of the third lens group G13 may be 10.5996mm, and a focal length fG4 of the fourth lens group G14 may be 22.3592mm.

A composite focal length fG12w of the first lens group G11 and the second lens group G12 at the wide-angle end may be-14.9327 mm, and a composite focal length fG12t of the first lens group G11 and the second lens group G12 at the telephoto end may be-29.2539 mm.

A refractive power kf of a first surface (e.g., an object-side surface of the eighth lens 180) of the fourth lens group G14 may be 0.0944mm, and a refractive power kr of a last surface (e.g., an image-side surface of the eighth lens 180) of the fourth lens group G14 may be-0.0597 mm.

In the first example, first lens group G11 as a whole may have positive refractive power, second lens group G12 as a whole may have negative refractive power, third lens group G13 as a whole may have positive refractive power, and fourth lens group G14 as a whole may have positive refractive power.

The first lens 110 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The second lens 120 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be flat.

The first lens 110 and the second lens 120 may be bonded to each other to form a bonded lens.

The reflective member R may be disposed behind the second lens 120.

The third lens 130 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The fourth lens 140 may have a negative refractive power, and the first and second surfaces thereof may be concave.

The fifth lens 150 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The fourth lens 140 and the fifth lens 150 may be combined with each other to form another combined lens.

The sixth lens 160 may have a positive refractive power, and the first and second surfaces thereof may be convex. The stop S may be disposed in front of the sixth lens 160.

The seventh lens 170 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The eighth lens 180 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The first surface of the sixth lens 160 may have aspherical coefficients as shown in table 3 below. That is, the object side surface of the sixth lens 160 may be aspherical.

TABLE 3

	S13
		Constant of quadratic curve (K)	-0.51693
Fourth order coefficient (A)	-3.805358E-04
		Coefficient of sixth order (B)	2.481040E-05
Coefficient of eighth order (C)	-5.132311E-06
		Coefficient of tenth order (D)	1.189786E-07

Fig. 3 is a development view showing a wide-angle end, a standard end, and a telephoto end of the second example of the optical imaging system when the object distance is infinity, and fig. 4 is a development view showing a wide-angle end, a standard end, and a telephoto end of the second example of the optical imaging system when the object distance is a short distance (600 mm).

Referring to fig. 3 and 4, a second example of an optical imaging system may include a first lens group G21, a second lens group G22, a third lens group G23, and a fourth lens group G24.

The first lens group G21 may include a first lens 210, a reflective member R, and a second lens 220, the second lens group G22 may include a third lens 230 and a fourth lens 240, the third lens group G23 may include a stop S, a fifth lens 250, and a sixth lens 260, and the fourth lens group G24 may include a seventh lens 270, in order from the object side.

In addition, the optical imaging system may further include a filter 290 and an image sensor IS.

The optical imaging system may focus an image on the imaging surface 291. The imaging plane 291 may refer to a surface on which an image is focused by the optical imaging system. As an example, the imaging plane 291 may refer to one surface of the image sensor IS on which light IS received.

The reflecting member R may be a prism, but may alternatively be a mirror.

At least one of the first lens group G21 to the fourth lens group G24 may be moved so as to change the total focal length of the optical imaging system. As an example, the first lens group G21 and the third lens group G23 are fixed, and the second lens group G22 moves along the optical axis to change the total focal length of the optical imaging system. That is, when the second lens group G22 moves from the object side toward the image side, the total focal length of the optical imaging system can be changed from the wide-angle end to the telephoto end.

Further, at least one of the first lens group G21 to the fourth lens group G24 may be moved so as to correct a focal position according to a variation in the total focal length of the optical imaging system. As an example, when the total focal length of the optical imaging system is changed from the wide-angle end to the telephoto end, the fourth lens group G24 may be moved from the image side toward the object side to correct the focal position.

Further, when the object distance is changed from infinity to a close distance (e.g., 600 mm), the fourth lens group G24 may be moved from the image side toward the object side.

The optical characteristics (radius of curvature, thickness of lens or distance between lenses, refractive index, abbe number, and focal length) of each element in the second example are listed in table 4 below.

TABLE 4

Table 5 below lists various other optical properties in the second example.

TABLE 5

In table 5, D0 is an object distance, D1 is an optical axis distance between the second lens 220 and the third lens 230, D2 is an optical axis distance between the fourth lens 240 and the stop S, D3 is an optical axis distance between the sixth lens 260 and the seventh lens 270, and D4 is an optical axis distance between the seventh lens 270 and the filter 290.

F is the total focal length of the optical imaging system, MAG is the magnification of the optical imaging system, FOV is the field of view of the optical imaging system, fno is the F-number of the optical imaging system, and TTL is the optical axis distance from the object side surface of the first lens 210 to the imaging surface 291.

The focal length fG1 of the first lens group G21 may be 38.7741mm, the focal length fG2 of the second lens group G22 may be-7.7549 mm, the focal length fG3 of the third lens group G23 may be 10.4556mm, and the focal length fG4 of the fourth lens group G24 may be 20.4823mm.

A composite focal length fG12w of the first lens group G21 and the second lens group G22 at the wide-angle end may be-16.2723 mm, and a composite focal length fG12t of the first lens group G21 and the second lens group G22 at the telephoto end may be-24.9821 mm.

A refractive power kf of a first surface (e.g., an object side surface of the seventh lens 270) of the fourth lens group G24 may be 0.1157mm, and a refractive power kr of a last surface (e.g., an image side surface of the seventh lens 270) of the fourth lens group G24 may be-0.0891 mm.

In the second example, the first lens group G21 as a whole may have a positive refractive power, the second lens group G22 as a whole may have a negative refractive power, the third lens group G23 as a whole may have a positive refractive power, and the fourth lens group G24 as a whole may have a positive refractive power.

The first lens 210 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be flat.

The second lens 220 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The reflective member R may be disposed between the first lens 210 and the second lens 220.

The third lens 230 may have a negative refractive power, and the first and second surfaces thereof may be concave.

The fourth lens 240 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The fifth lens 250 may have a positive refractive power, and the first and second surfaces thereof may be convex. The stop S may be disposed in front of the fifth lens 250.

The sixth lens 260 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The seventh lens 270 may have a positive refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The first surface of the fifth lens 250 may have aspherical coefficients as shown in table 6 below. That is, the object side surface of the fifth lens 250 may be aspherical.

TABLE 6

	S12
		Second order constant (K)	-0.34792
Fourth order coefficient (A)	-3.390915E-04
		Coefficient of sixth order (B)	-2.210576E-05
Coefficient of eighth order (C)	-1.690132E-06
		Coefficient of tenth order (D)	9.416985E-09

Fig. 5 is a development view showing a wide-angle end, a standard end, and a telephoto end of a third example of the optical imaging system when the object distance is infinite, and fig. 6 is a development view showing a wide-angle end, a standard end, and a telephoto end of the third example of the optical imaging system when the object distance is a short distance (600 mm).

Referring to fig. 5 and 6, a third example of an optical imaging system may include a first lens group G31, a second lens group G32, a third lens group G33, and a fourth lens group G34.

The first lens group G31 may include a first lens 310, a second lens 320, and a reflective member R, the second lens group G32 may include a third lens 330 and a fourth lens 340, the third lens group G33 may include a stop S, a fifth lens 350, and a sixth lens 360, and the fourth lens group G34 may include a seventh lens 370, in order from the object side.

In addition, the optical imaging system may further include an optical filter 390 and an image sensor IS.

The optical imaging system may focus an image on an imaging plane 391. Imaging plane 391 may refer to a surface on which an image is focused by an optical imaging system. As an example, the imaging plane 391 may refer to one surface of the image sensor IS on which light IS received.

The reflecting member R may be a prism, but may alternatively be a mirror.

At least one of the first lens group G31 to the fourth lens group G34 may be moved so as to change the overall focal length of the optical imaging system. As an example, the first lens group G31 and the third lens group G33 are fixed, and the second lens group G32 is moved along the optical axis to change the total focal length of the optical imaging system. That is, when the second lens group G32 is moved from the object side toward the image side, the total focal length of the optical imaging system can be changed from the wide-angle end to the telephoto end.

Further, at least one of the first lens group G31 to the fourth lens group G34 may be moved so as to correct a focal position according to a change in the total focal length of the optical imaging system. As an example, when the total focal length of the optical imaging system is changed from the wide-angle end to the telephoto end, the fourth lens group G34 may be moved from the image side toward the object side to correct the focal position.

Further, when the object distance is changed from infinity to a close distance (e.g., 600 mm), the fourth lens group G34 may be moved from the image side toward the object side.

Optical characteristics (radius of curvature, thickness of lens or distance between lenses, refractive index, abbe number, and focal length) of each element of the third example are listed in table 7 below.

TABLE 7

Table 8 below lists various other optical characteristics in the third example.

TABLE 8

In table 8, D0 is an object distance, D1 is an optical axis distance between the reflecting member R and the third lens 330, D2 is an optical axis distance between the fourth lens 340 and the stop S, D3 is an optical axis distance between the sixth lens 360 and the seventh lens 370, and D4 is an optical axis distance between the seventh lens 370 and the filter 390.

F is the total focal length of the optical imaging system, MAG is the magnification of the optical imaging system, FOV is the field of view of the optical imaging system, fno is the F-number of the optical imaging system, and TTL is the optical axis distance from the object side of the first lens 310 to the imaging plane 391.

The focal length fG1 of the first lens group G31 may be 27.4666mm, the focal length fG2 of the second lens group G32 may be-7.3579 mm, the focal length fG3 of the third lens group G33 may be 10.2712mm, and the focal length fG4 of the fourth lens group G34 may be 24.9239mm.

The composite focal length fG12w of the first lens group G31 and the second lens group G32 at the wide-angle end may be-14.357 mm, and the composite focal length fG12t of the first lens group G31 and the second lens group G32 at the telephoto end may be-26.591 mm.

A refractive power kf of a first surface (e.g., an object-side surface of the seventh lens 370) of the fourth lens group G34 may be 0.1011mm, and a refractive power kr of a last surface (e.g., an image-side surface of the seventh lens 370) of the fourth lens group G34 may be-0.0703 mm.

In the third example, the first lens group G31 as a whole may have a positive refractive power, the second lens group G32 as a whole may have a negative refractive power, the third lens group G33 as a whole may have a positive refractive power, and the fourth lens group G34 as a whole may have a positive refractive power.

The first lens 310 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The second lens 320 may have a positive optical power, and a first surface thereof may be convex and a second surface thereof may be flat.

The first lens 310 and the second lens 320 may be bonded to each other to form a bonded lens.

The reflective member R may be disposed behind the second lens 320.

The third lens 330 may have a negative refractive power, and the first and second surfaces thereof may be concave.

The fourth lens 340 may have a positive optical power, and a first surface thereof may be convex and a second surface thereof may be concave.

The fifth lens 350 may have a positive refractive power, and the first and second surfaces thereof may be convex. The stop S may be disposed in front of the fifth lens 350.

The sixth lens 360 may have a negative refractive power, and a first surface thereof may be convex and a second surface thereof may be concave.

The seventh lens 370 may have positive optical power, and a first surface thereof may be convex and a second surface thereof may be concave.

The second surface of the fifth lens 350 may have aspherical coefficients as shown in table 9 below. That is, the image side surface of the fifth lens 350 may be aspherical.

TABLE 9

	S13
		Constant of quadratic curve (K)	-0.3551
Fourth order coefficient (A)	-2.962413E-04
		Coefficient of sixth order (B)	-1.479960E-05
Coefficient of eighth order (C)	2.944110E-06
		Coefficient of tenth order (D)	-8.737973E-08

Table 10 below lists the values of fG1, fG2, fG3, fG4, fGc, fG12w, fG12t, kf, kr, laf, D13 and TTL and the values of the amounts of D13/TTL, D13/fG1, fGc/fG2, kf/kr, fG12w/fG12t and Laf/fG4 in the conditional expressions 1 to 6 of the first to third examples. As can be seen from table 10, all of the first to third examples satisfy all of conditional expressions 1 to 6.

Watch 10

As described above, the examples of the optical imaging system described above can realize the zoom function by changing the focal length.

While the present disclosure includes specific examples, it will be apparent upon an understanding of the present disclosure that various changes in form and detail may be made to these examples without departing from the spirit and scope of the claims and their equivalents. Therefore, the scope of the present disclosure is defined not by the specific embodiments but by the claims and their equivalents, and all modifications within the scope of the claims and their equivalents should be understood as being included in the present disclosure.

Claims (20)

1. An optical imaging system comprising:

a first lens group, a second lens group, a third lens group, and a fourth lens group that are provided in this order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system; and

an image sensor configured to convert an image of an object incident on the image sensor through the first to fourth lens groups into an electrical signal,

wherein at least one lens group among the first lens group to the fourth lens group is configured to be movable along the optical axis,

the first lens group has positive refractive power and includes a reflective member and at least one lens disposed between the object side and the second lens group of the optical imaging system, and

the at least one lens is configured to refract light passing through the at least one lens to condense the light to be incident on the reflecting member.

2. The optical imaging system of claim 1, wherein the at least one lens of the first lens group includes a first lens and a second lens disposed in order along the optical axis from the object side of the optical imaging system toward the imaging surface of the optical imaging system,

the first lens is disposed between the object side of the optical imaging system and the reflecting member, and

the second lens is disposed between the object side of the optical imaging system and the reflection member, or between the reflection member and the second lens group.

3. The optical imaging system according to claim 2, wherein one of the first lens and the second lens has an abbe number of 50 or more, and the other of the first lens and the second lens has an abbe number of 40 or less.

4. The optical imaging system of claim 2, wherein one of the first and second lenses has a positive optical power and the other of the first and second lenses has a negative optical power, and

an abbe number of a lens having a positive refractive power among the first lens and the second lens is 50 or more, and an abbe number of a lens having a negative refractive power among the first lens and the second lens is 40 or less.

5. The optical imaging system of claim 1, wherein the second lens group has a negative refractive power and is configured to be movable away from the object side of the optical imaging system toward the imaging surface of the optical imaging system to narrow a field of view of the optical imaging system and movable away from the imaging surface of the optical imaging system toward the object side of the optical imaging system to expand the field of view of the optical imaging system.

6. The optical imaging system of claim 5, wherein the second lens group includes a plurality of lenses having negative compound power, and

any one of the plurality of lenses of the second lens group has a concave object side surface and a concave image side surface.

7. The optical imaging system of claim 6, wherein 0.6 ≦ fGc/fG2 ≦ 0.9 is satisfied, where fGc is a focal length of the lens having a concave object side surface and a concave image side surface, and fG2 is a focal length of the second lens group.

8. The optical imaging system of claim 5, wherein the first lens group and the third lens group are disposed at fixed positions on the optical axis, and

the fourth lens group is configured to be movable away from the imaging surface of the optical imaging system toward the object side of the optical imaging system to correct a focal position of the optical imaging system when the second lens group is moved away from the object side of the optical imaging system toward the imaging surface of the optical imaging system to narrow the field of view of the optical imaging system, and to be movable away from the object side of the optical imaging system toward the imaging surface of the optical imaging system to correct the focal position of the optical imaging system when the second lens group is moved away from the imaging surface of the optical imaging system toward the object side of the optical imaging system to widen the field of view of the optical imaging system.

9. The optical imaging system of claim 8, wherein-1.8 ≦ kf/kr ≦ -1.2, where kf is a refractive power of a first surface of the fourth lens group closest to the object side of the optical imaging system, and kr is a refractive power of a last surface of the fourth lens group closest to the imaging surface of the optical imaging system.

10. The optical imaging system of claim 8, wherein the fourth lens group is further configured to be movable away from the imaging plane of the optical imaging system toward the object side of the optical imaging system when an object distance changes from an infinite number to a close distance, and

satisfy 0 ≦ Laf/fG4 ≦ 0.1, where Laf is an amount of movement of the fourth lens group when an object distance changes from infinity to a close distance at a telephoto end of the optical imaging system where the field of view of the optical imaging system is narrowest, and fG4 is a focal length of the fourth lens group.

11. The optical imaging system of claim 8, wherein the third lens group and the fourth lens group each have positive refractive power.

12. The optical imaging system of claim 5, wherein the third lens group includes a diaphragm and a plurality of lenses disposed in order along the optical axis away from the object side of the optical imaging system toward the imaging surface of the optical imaging system, and

a lens disposed closest to the stop among the plurality of lenses of the third lens group has a positive refractive power.

13. The optical imaging system of claim 12, wherein an object-side or image-side surface of the lens disposed closest to the stop is aspheric.

14. The optical imaging system of claim 12, wherein the first surface of the first lens group is a surface of the first lens group disposed on the object side of the optical imaging system, and

0.4 ≦ D13/TTL ≦ 0.6 is satisfied, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and TTL is an optical axis distance from the first surface of the first lens group to the imaging surface.

15. The optical imaging system of claim 12, wherein the first surface of the first lens group is a surface of the first lens group disposed on the object side of the optical imaging system, and

0.4 ≦ D13/fG1 ≦ 0.8 is satisfied, where D13 is an optical axis distance from the first surface of the first lens group to the stop, and fG1 is a focal length of the first lens group.

16. The optical imaging system according to claim 5, wherein 0.4 ≦ fG12w/fG12t ≦ 0.7, where fG12w is a composite focal length of the first lens group and the second lens group at a wide angle end of the optical imaging system where the field of view of the optical imaging system is widest, and fG12t is a composite focal length of the first lens group and the second lens group at a telephoto end of the optical imaging system where the field of view of the optical imaging system is narrowest.

17. An optical imaging system comprising:

a first lens group, a second lens group, a third lens group, and a fourth lens group that are disposed in this order from an object side of the optical imaging system toward an imaging surface of the optical imaging system along an optical axis of the optical imaging system; and

an image sensor configured to convert an image of an object incident on the image sensor through the first to fourth lens groups into an electrical signal,

wherein one lens group among the first lens group to the fourth lens group is configured to be movable along the optical axis to change a focal length of the optical imaging system,

another lens group among the first lens group to the fourth lens group is configured to be movable along the optical axis to correct a focal position of the optical imaging system, and

the first lens group includes a reflecting member configured to change a path of light incident on the reflecting member, and at least one lens configured to condense the light entering the optical imaging system onto the reflecting member.

18. The optical imaging system of claim 17, wherein the first lens group and the third lens group are disposed at fixed positions on the optical axis,

the second lens group is configured to be movable along the optical axis to change the focal length of the optical imaging system, an

The fourth lens group is configured to be movable along the optical axis to correct the focal position of the optical imaging system when the second lens group is moved along the optical axis to change the focal length of the optical imaging system.

19. The optical imaging system of claim 18, wherein the second lens group and the fourth lens group are further configured to be movable in opposite directions relative to each other along the optical axis when the second lens group is moved along the optical axis to change the focal length of the optical imaging system, and the fourth lens group is moved along the optical axis to correct the focal position of the optical imaging system when the second lens group is moved along the optical axis to change the focal length of the optical imaging system.

20. The optical imaging system of claim 17, wherein the other lens group among the first through fourth lens groups is further configured to be movable along the optical axis when an object distance varies between an infinite and close distance.

Images