CN212379643U

CN212379643U - Optical imaging system

Info

Publication number: CN212379643U
Application number: CN202021284539.1U
Authority: CN
Inventors: 张永明; 赖建勋; 刘燿维
Original assignee: Ability Opto Electronics Technology Co Ltd
Current assignee: Ability Opto Electronics Technology Co Ltd
Priority date: 2020-04-20
Filing date: 2020-07-03
Publication date: 2021-01-19
Anticipated expiration: 2030-07-03
Also published as: TWM600850U

Abstract

The utility model discloses an optical imaging system comprises a first lens, a second lens, a third lens and a fourth lens according to the preface from an object side to an image side. The first lens element with positive refractive power has a convex object-side surface. The second lens element to the third lens element have refractive power, and both surfaces of each of the lens elements may be aspheric. The fourth lens element with negative refractive power has a concave image-side surface, wherein both surfaces of the fourth lens element are aspheric, and at least one surface of the fourth lens element has an inflection point. The lens elements with refractive power in the optical imaging system are the first lens element to the fourth lens element. When the specific conditions are met, the optical imaging device can have larger light receiving capacity and better optical path adjusting capacity so as to improve the imaging quality.

Description

Optical imaging system

Technical Field

The utility model relates to an optical imaging system, and especially relate to a be applied to miniaturized optical imaging system on the electronic product.

Background

In recent years, with the rise of portable electronic products having a photographing function, the demand for optical systems has been increasing. The photosensitive elements of a general optical system are not limited to a Charge Coupled Device (CCD) or a Complementary Metal-Oxide Semiconductor (CMOS) Sensor, and with the refinement of Semiconductor process technology, the pixel size of the photosensitive elements is reduced, and the optical system gradually develops to the high pixel field, so the requirement for the imaging quality is also increasing.

The conventional optical system mounted on the portable device mainly adopts a two-piece or three-piece lens structure, however, the portable device is continuously lifting pixels and the terminal consumer needs a large aperture, such as a low light and night photographing function, or a wide viewing angle, such as a self-photographing function of a front lens. However, the optical system with large aperture is often subject to the situation of generating more aberrations, which results in the degradation of peripheral image quality and the difficulty of manufacturing, and the optical system with wide viewing angle is subject to the increase of distortion (distortion), so the conventional optical imaging system can not satisfy the higher-order photographing requirement.

Therefore, how to effectively increase the light-entering amount of the optical imaging system and increase the viewing angle of the optical imaging system, not only further improving the total pixels and quality of the image, but also simultaneously considering the balance design of the miniaturized optical imaging system, becomes a very important issue.

SUMMERY OF THE UTILITY MODEL

The utility model provides an optical imaging system can utilize the combination of the refractive power of four lenses, convex surface and concave surface (convex surface or concave surface mean the object side or the image side of each lens in principle describe in the epaxial geometry), and then effectively improve optical imaging system's the light inlet and increase optical imaging system's visual angle, improve the total pixel and the quality of formation of image simultaneously to be applied to on miniature electronic product.

The utility model provides an optical imaging system can focus and reach the certain performance respectively to visible light and infrared ray (bimodulus) simultaneously to the object side or the image side of its fourth lens are provided with anti-curved point, can effectively adjust each visual field incident in the angle of fourth lens, and revise to optical distortion and TV distortion. In addition, the surface of the fourth lens can have better optical path adjusting capability so as to improve the imaging quality.

According to the present invention, an optical imaging system includes, in order from an object side to an image side, a first lens element with negative refractive power having a concave object-side surface and at least one inflection point; a second lens element with refractive power; a third lens element with positive refractive power having a concave object-side surface on an optical axis; a fourth lens element with refractive power; and an imaging plane; wherein four lenses having refractive power in the optical imaging system, at least one of the second lens element and the fourth lens element has positive refractive power, focal lengths of the first lens element to the fourth lens element are respectively f1, f2, f3 and f4, the focal length of the optical imaging system is f, an entrance pupil diameter of the optical imaging system is HEP, a distance HOS is provided on an optical axis from an object-side surface of the first lens element to the image plane, a distance idtl is provided on the optical axis from the object-side surface of the first lens element to the image-side surface of the fourth lens element, a half of a maximum visual angle of the optical imaging system is HAF, thicknesses of the first lens element, the second lens element, the third lens element and the fourth lens element, which are at a height of 1/2HEP and parallel to the optical axis, are respectively ETP1, ETP2, ETP3 and ETP4, a sum of the ETP1 to ETP4 is SETP, and a sum of the first lens element is SETP 4, The thicknesses of the second lens, the third lens and the fourth lens on the optical axis are TP1, TP2, TP3 and TP4 respectively, the sum of the TP1 to the TP4 is STP, and the following conditions are satisfied: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.5 ≤ SETP/STP < 1.

Preferably, a horizontal distance parallel to the optical axis between a coordinate point on the object-side surface of the first lens at a height of 1/2HEP and the image plane is ETL, and a horizontal distance parallel to the optical axis between a coordinate point on the object-side surface of the first lens at a height of 1/2HEP and a coordinate point on the image-side surface of the fourth lens at a height of 1/2HEP is EIN, wherein the following conditions are satisfied: EIN/ETL is more than or equal to 0.2 and less than 1.

Preferably, the optical imaging system satisfies the following formula: SETP/EIN is more than or equal to 0.3 and less than 1.

Preferably, the second lens element with positive refractive power has a concave object-side surface on an optical axis.

Preferably, an image-side surface of the first lens element is convex on an optical axis and an image-side surface of the second lens element is convex on the optical axis.

Preferably, the image-side surface of the third lens is convex on the optical axis.

Preferably, the object-side surface and the image-side surface of the fourth lens are convex on the optical axis.

Preferably, the imaging height of the optical imaging system is HOI, and the modulation conversion contrast transfer rates of the three optical axes of visible light, 0.3HOI and 0.7HOI on the imaging plane at the spatial frequency of 55cycles/mm are respectively expressed by MTFE0, MTFE3 and MTFE7, which satisfy the following conditions: MTFE0 is more than or equal to 0.2; MTFE3 is more than or equal to 0.01; and MTFE7 is not less than 0.01.

Preferably, the optical imaging device further comprises an aperture, and a distance InS is formed between the aperture and the imaging plane on the optical axis, which satisfies the following formula: 0.2-1.1 of InS/HOS.

According to another aspect of the present invention, an optical imaging system includes, in order from an object side to an image side, a first lens element with negative refractive power having a concave object-side surface and at least one inflection point; a second lens element with refractive power; a third lens element with positive refractive power having a concave object-side surface on an optical axis and at least one inflection point; a fourth lens element with refractive power; and an imaging plane; wherein four lenses having refractive power in the optical imaging system, at least one of the second lens element and the fourth lens element has positive refractive power, the focal lengths from the first lens element to the fourth lens element are f1, f2, f3 and f4, respectively, the focal length of the optical imaging system is f, the diameter of the entrance pupil of the optical imaging system is HEP, a distance HOS is provided from the object-side surface of the first lens element to the image plane on the optical axis, a distance idtl is provided from the object-side surface of the first lens element to the image-side surface of the fourth lens element on the optical axis, a half of the maximum visible angle of the optical imaging system is HAF, a horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the image plane parallel to the optical axis is ETL, a horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the image-side surface of the fourth lens element parallel to the HEP height of 1/2 on the image-side surface is EIN Which satisfies the following conditions: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.2 ≤ EIN/ETL < 1.

Preferably, the imaging height of the optical imaging system is HOI, and the optical axis of visible light on the imaging plane, 0.3HOI and 0.7HOI are expressed by MTFQ0, MTFQ3 and MTFQ7 respectively as modulation conversion contrast transfer rates at a spatial frequency of 110cycles/mm, which satisfy the following conditions: MTFQ0 is more than or equal to 0.2; MTFQ3 is more than or equal to 0.01; and MTFQ7 is more than or equal to 0.01.

Preferably, the optical imaging system satisfies the following formula: HOS is more than 0mm and less than or equal to 4 mm.

Preferably, the thickness of the second lens at 1/2HEP height and parallel to the optical axis is ETP2, the thickness of the second lens on the optical axis is TP2, which satisfies the following conditions: ETP2/TP2 of 0.1-5.

Preferably, the optical imaging system satisfies the following condition: -3. ltoreq. f2/f 3. ltoreq.5.

Preferably, the optical imaging system satisfies the following condition: f2< f 3.

Preferably, the optical imaging system satisfies the following condition: -2. ltoreq. f1/f 4. ltoreq.3.

Preferably, the thicknesses of the second lens and the third lens on the optical axis are TP2 and TP3, respectively, which satisfy the following conditions: TP2/TP3 is more than or equal to 0.1 and less than or equal to 10.

Preferably, the thicknesses of the second lens and the third lens on the optical axis are TP2 and TP3, respectively, which satisfy the following conditions: TP2> TP 3.

According to another aspect of the present invention, an optical imaging system includes, in order from an object side to an image side, a first lens element with negative refractive power having a concave object-side surface and a convex image-side surface, the object-side surface and the image-side surface each having at least one inflection point; a second lens element with positive refractive power having a concave object-side surface on an optical axis; a third lens element with positive refractive power having a concave object-side surface on an optical axis and at least one inflection point; a fourth lens element with refractive power; and an imaging plane; wherein the optical imaging system comprises four lenses with refractive power, the focal lengths of the first lens element to the fourth lens element are f1, f2, f3 and f4, respectively, the focal length of the optical imaging system is f, the diameter of the entrance pupil of the optical imaging system is HEP, the distance HOS is between the object-side surface of the first lens element and the imaging surface along the optical axis, the distance idtl is between the object-side surface of the first lens element and the image-side surface of the fourth lens element along the optical axis, half of the maximum viewing angle of the optical imaging system is HAF, the horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the imaging surface along the optical axis is ETL, the horizontal distance between the point at the HEP height of 1/2 on the object-side surface of the first lens element and the coordinate point at the HEP height of 1/2 on the image-side surface of the fourth lens element along the optical axis is EIN, it satisfies the following conditions: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.2 ≤ EIN/ETL < 1.

Preferably, the distance between the third lens and the fourth lens on the optical axis is IN34, and the following formula is satisfied: 0< IN34/f is less than or equal to 5.

Preferably, the optical imaging system satisfies the following condition: f2/f3 is more than or equal to 0.1 and less than or equal to 5.

Preferably, the object-side surface and the image-side surface of the fourth lens are both concave on the optical axis.

Preferably, the image side surface of the fourth lens has at least two points of inflection.

Preferably, the optical imaging system further includes an aperture stop, an image sensor disposed on the image plane and having a distance InS from the aperture stop to the image plane, and a driving module coupled to the first lens element to the fourth lens element for displacing the first lens element to the fourth lens element, wherein the following formula is satisfied: 0.2-1.1 of InS/HOS.

The thickness of the single lens at the height of 1/2 entrance pupil diameter (HEP) particularly affects the ability of the shared field of view of each ray within the range of 1/2 entrance pupil diameter (HEP) to correct aberration and the optical path difference between the rays of each field of view, and the larger the thickness, the higher the ability to correct aberration is, however, the more difficult it is to manufacture, so that the thickness of the single lens at the height of 1/2 entrance pupil diameter (HEP) must be controlled, particularly the proportional relationship (ETP/TP) between the thickness (ETP) of the lens at the height of 1/2 entrance pupil diameter (HEP) and the Thickness (TP) of the lens on the optical axis belonging to the surface must be controlled. For example, the thickness of the first lens at 1/2 entrance pupil diameter (HEP) height is indicated by ETP 1. The thickness of the second lens at 1/2 entrance pupil diameter (HEP) height is indicated by ETP 2. The thickness of the remaining lenses in the optical imaging system at 1/2 entrance pupil diameter (HEP) height, and so forth. The sum of ETP1 to ETP4 is SETP, and the embodiments of the present invention can satisfy the following formula: SETP/EIN is more than or equal to 0.3 and less than 1.

In order to balance the ability to correct aberrations well and reduce manufacturing difficulties, it is particularly desirable to control the ratio (ETP/TP) between the thickness (ETP) of the lens at the 1/2 entrance pupil diameter (HEP) height and the Thickness (TP) of the lens on the optical axis. For example, the thickness of the first lens at 1/2 entrance pupil diameter (HEP) height is represented by ETP1, the thickness of the first lens on the optical axis is TP1, and the ratio of the two is ETP1/TP 1. The thickness of the second lens at 1/2 entrance pupil diameter (HEP) height is shown as ETP2, and the thickness of the second lens on the optical axis is TP2, the ratio of which is ETP2/TP 2. The proportional relationship between the thickness of the remaining lenses in the optical imaging system at the height of the entrance pupil diameter (HEP) at 1/2 and the thickness of the lens on the optical axis (TP) is expressed by analogy. The embodiment of the utility model can satisfy following formula: 0< ETP/TP.ltoreq.5, preferably 0.1. ltoreq. ETP/TP.ltoreq.5.

The horizontal distance between two adjacent lenses at the height of 1/2 entrance pupil diameter (HEP) is represented by ED, which is parallel to the optical axis of the optical imaging system and particularly affects the ability of the 1/2 entrance pupil diameter (HEP) position to correct the aberration in the shared region of each light field and the optical path difference between the light beams in each field, and the larger the horizontal distance, the higher the ability to correct the aberration is, but also increases the difficulty of manufacturing and limits the degree of "shrinkage" of the length of the optical imaging system, so that the horizontal distance (ED) between two adjacent lenses at the height of 1/2 entrance pupil diameter (HEP) must be controlled.

IN order to balance the difficulty of improving the aberration correction capability and reducing the length "shrink" of the optical imaging system, it is particularly necessary to control the ratio (ED/IN) between the horizontal distance (ED) between the adjacent two lenses at the height of the 1/2 entrance pupil diameter (HEP) and the horizontal distance (IN) between the adjacent two lenses on the optical axis. For example, the horizontal distance between the first lens and the second lens at the entrance pupil diameter (HEP) height of 1/2 is represented by ED12, the horizontal distance between the first lens and the second lens on the optical axis is IN12, and the ratio of ED12/IN 12. The horizontal distance between the second lens and the third lens at the entrance pupil diameter (HEP) height of 1/2 is denoted as ED23, and the horizontal distance between the second lens and the third lens on the optical axis is IN23, and the ratio of ED23/IN 23. The proportional relationship between the horizontal distance of the other two adjacent lenses in the optical imaging system at the height of the 1/2 entrance pupil diameter (HEP) and the horizontal distance of the two adjacent lenses on the optical axis is represented by the way of analogy.

The horizontal distance that is on a parallel with the optical axis between the coordinate point of 1/2HEP height to this imaging surface on this fourth lens image side is EBL, and the horizontal distance that is on a parallel with the optical axis with the nodical to this imaging surface of optical axis on this fourth lens image side is BL, the embodiment of the utility model discloses an improve the ability of revising the aberration and reserve other optical element's accommodation space for the while balance, can satisfy following formula: EBL/BL is more than or equal to 0.1 and less than or equal to 1.5.

The optical imaging system may further include a filter element, the filter element is located between the fourth lens element and the image plane, a distance between a coordinate point of 1/2HEP height on the image side surface of the fourth lens element and the filter element, which is parallel to the optical axis, is EIR, a distance between a point of the optical axis on the image side surface of the fourth lens element and the filter element, which is parallel to the optical axis, is PIR, and the following formula can be satisfied by embodiments of the present invention: EIR/PIR is more than or equal to 0.1 and less than or equal to 1.1.

The optical imaging system can be used to cooperate with an image sensor device having a diagonal dimension of 1/1.2 inch or less, wherein the size of the image sensor device is preferably 1/2.3 inch, the pixel size of the image sensor device is less than 1.4 micrometer (μm), preferably less than 1.12 micrometer (μm), and most preferably less than 0.9 micrometer (μm). In addition, the optical imaging system can be applied to an image sensing element with the length-width ratio of 16: 9.

The optical imaging system can be suitable for the recording requirement (such as 4K2K or UHD, QHD) of more than million or ten million pixels and has good imaging quality.

When f1 | > f4, the total Height (HOS) of the optical imaging System can be reduced to achieve miniaturization.

When |/f 2 | + -f 3 | f1 | + | f4 |, at least one of the second lens element to the third lens element has weak positive refractive power or weak negative refractive power. The term "weak refractive power" refers to the absolute value of the focal length of a particular lens element greater than 10 mm. When the present invention is used, at least one of the second lens element and the third lens element has weak positive refractive power, which effectively shares the positive refractive power of the first lens element to avoid the occurrence of unnecessary aberration too early, otherwise, if at least one of the second lens element and the third lens element has weak negative refractive power, the aberration of the correction system can be finely adjusted.

The fourth lens element with negative refractive power has a concave image-side surface. Thereby, it is advantageous to shorten the back focal length to maintain miniaturization. In addition, at least one surface of the fourth lens element can have at least one point of inflection, which can effectively suppress the incident angle of the light in the off-axis field of view, and further correct the aberration in the off-axis field of view.

Compared with the prior art, the utility model discloses one of following advantage has at least:

the utility model discloses an optical imaging system comprises a first lens, a second lens, a third lens and a fourth lens according to the preface from an object side to an image side. The first lens element with positive refractive power has a convex object-side surface. The second lens element to the third lens element have refractive power, and both surfaces of the lens elements may be aspheric. The fourth lens element with negative refractive power has a concave image-side surface, wherein both surfaces of the fourth lens element are aspheric, and at least one surface of the fourth lens element has an inflection point. The lens elements with refractive power in the optical imaging system are the first lens element to the fourth lens element. When the specific conditions are met, the optical imaging device can have larger light receiving capacity and better optical path adjusting capacity so as to improve the imaging quality.

Drawings

Fig. 1 is a schematic view of an optical imaging system of a first embodiment of the present invention;

fig. 2 is a graph of spherical aberration, astigmatism, and optical distortion of the optical imaging system of the first embodiment of the invention;

fig. 3 is a diagram of visible spectrum modulation conversion characteristics of the optical imaging system according to the first embodiment of the present invention;

fig. 4 is a schematic view of an optical imaging system of a second embodiment of the present invention;

fig. 5 is a graph of spherical aberration, astigmatism, and optical distortion of an optical imaging system of a second embodiment of the invention;

fig. 6 is a diagram of visible spectrum modulation conversion characteristics of a second embodiment optical imaging system of the present invention;

fig. 7 is a schematic view of an optical imaging system of a third embodiment of the present invention;

fig. 8 is a graph of spherical aberration, astigmatism, and optical distortion of an optical imaging system of a third embodiment of the invention;

fig. 9 is a diagram of visible spectrum modulation conversion characteristics of a third embodiment optical imaging system of the present invention;

fig. 10 is a schematic view of an optical imaging system of a fourth embodiment of the present invention;

fig. 11 is a graph showing spherical aberration, astigmatism and optical distortion of an optical imaging system according to a fourth embodiment of the present invention;

fig. 12 is a diagram of visible spectrum modulation conversion characteristics of a fourth embodiment optical imaging system of the present invention;

fig. 13 is a schematic view of an optical imaging system of a fifth embodiment of the present invention;

fig. 14 is a graph of spherical aberration, astigmatism, and optical distortion of the optical imaging system of the fifth embodiment of the invention;

fig. 15 is a diagram of visible spectrum modulation conversion characteristics of an optical imaging system according to a fifth embodiment of the present invention;

fig. 16 is a schematic view of an optical imaging system of a sixth embodiment of the present invention;

fig. 17 is a graph of spherical aberration, astigmatism, and optical distortion of an optical imaging system of a sixth embodiment of the invention;

fig. 18 is a diagram showing a visible light spectrum modulation conversion characteristic of an optical imaging system according to a sixth embodiment of the present invention.

Reference numerals and tabular notation: 10,20,30,40,50,60: optical imaging system 100,200,300,400,500,600: aperture 110,210,310,410,510,610: first lens; 112,212,312,412,512,612, object side; 114,214,314,414,514,614 image side; 120,220,320,420,520,620, a second lens; 122,222,322,422,522,622, object side; 124,224,324,424,524,624 image side; 130,230,330,430,530,630, a third lens; 132,232,332,432,532,632, object side; 134,234,334,434,534,634 image side; 140,240,340,440,540,640, a fourth lens; 142,242,342,442,542,642, object side; 144,244,344,444,544,644 image side; 170,270,370,470,570,670 infrared filter; 180,280,380,480,580,680, imaging surface; 190,290,390,490,590,690 image sensor element; f, focal length of the optical imaging system; f1, f2, f3, f4 focal lengths of the first lens to the fourth lens; F/HEP, Fno, F #: aperture value of the optical imaging system; HAF, half of the maximum viewing angle of the optical imaging system; NA1, abbe number of the first lens; NA2, NA3, NA4 Abbe numbers of second to fourth lenses; r1, R2 radius of curvature of the object-side and image-side surfaces of the first lens; r3, R4 radius of curvature of the object-side and image-side surfaces of the second lens; r5, R6 radius of curvature of object side and image side of the third lens; r7, R8 radius of curvature of object side and image side of the fourth lens; TP1 thickness of the first lens on the optical axis; TP2, TP3, TP4 thicknesses of the second to fourth lenses on the optical axis; Σ TP is the sum of the thicknesses of all the lenses with refractive power; IN12, the distance between the first lens and the second lens on the optical axis; IN23, the distance between the second lens and the third lens on the optical axis; IN34, the distance between the third lens and the fourth lens on the optical axis; InRS41 horizontal displacement distance from the intersection point of the object side surface of the fourth lens on the optical axis to the maximum effective radius position of the object side surface of the fourth lens on the optical axis; IF411, the point of inflection on the object-side surface of the fourth lens closest to the optical axis; SGI411 amount of subsidence of this point; HIF411 is the vertical distance between the inflection point closest to the optical axis on the object-side surface of the fourth lens and the optical axis; IF421, the point of inflection closest to the optical axis on the image-side surface of the fourth lens; SGI421: amount of subsidence of this point; HIF421, vertical distance between the inflection point closest to the optical axis and the optical axis on the image-side surface of the fourth lens; IF412, a second point of inflection near the optical axis on the object-side surface of the fourth lens; SGI412 the amount of subsidence of this point; HIF412, vertical distance between the second inflection point near the optical axis and the optical axis of the object-side surface of the fourth lens; IF422, a second inflection point near the optical axis on the image-side surface of the fourth lens; SGI422 the amount of subsidence at this point; HIF422 is the vertical distance between the second inflection point close to the optical axis on the image side of the fourth lens and the optical axis; IF413 the third point of inflection near the optical axis on the object-side of the fourth lens; SGI413 amount of subsidence of this point; HIF413 vertical distance between the third inflection point near the optical axis and the optical axis on the object-side surface of the fourth lens; an IF423, a third inflection point on the image-side surface of the fourth lens, which is close to the optical axis; SGI423 amount of this point subsidence; HIF423, vertical distance between the third inflection point close to the optical axis and the optical axis on the image side surface of the fourth lens; IF414, fourth point of inflection near the optical axis on the object-side of the fourth lens; SGI414 amount of subsidence at this point; HIF414 vertical distance between the fourth inflection point near the optical axis and the optical axis of the fourth lens object-side surface; IF424, fourth inflection point near the optical axis on the image-side surface of the fourth lens; SGI424 the amount of subsidence of this point; HIF424, vertical distance between the fourth inflection point near the optical axis and the optical axis on the image-side surface of the fourth lens; c41 critical point of object side of the fourth lens; c42 critical point of image side surface of the fourth lens; SGC41 horizontal displacement distance between the critical point of the object side surface of the fourth lens and the optical axis; SGC42 horizontal displacement distance between the critical point of the image side surface of the fourth lens and the optical axis; HVT41 is the perpendicular distance between the critical point of the object side surface of the fourth lens and the optical axis; HVT42 is the vertical distance between the critical point of the image side surface of the fourth lens and the optical axis; HOS, total system height (distance from the object side surface of the first lens to the imaging surface on the optical axis); dg is the diagonal length of the image sensing device; InS is the distance from the diaphragm to the imaging surface; the InTL is the distance from the object side surface of the first lens to the image side surface of the fourth lens; InB is the distance from the image side surface of the fourth lens to the imaging surface; HOI, half of diagonal length (maximum image height) of effective sensing area of image sensing element; TDT is TV Distortion (TV Distortion) of the optical imaging system during imaging; ODT is the Optical Distortion (Optical Distortion) of an Optical imaging system during image formation.

Detailed Description

The embodiment of the present invention relates to the following terms and their code numbers of the lens parameters, which are used as the reference for the following description:

lens parameters related to length or height: the imaging height of the optical imaging system is represented by HOI; the height of the optical imaging system is denoted by HOS; the distance between the object side surface of the first lens and the image side surface of the fourth lens of the optical imaging system is represented by InTL; the distance between the image side surface of the fourth lens of the optical imaging system and the imaging surface is represented by InB; instl + InB ═ HOS; the distance between a fixed diaphragm (aperture) of the optical imaging system and an imaging surface is represented by InS; the distance between the first lens and the second lens of the optical imaging system is denoted (exemplified) by IN 12; the thickness of the first lens of the optical imaging system on the optical axis is denoted by TP1 (illustrated).

Material dependent lens parameters: the abbe number of the first lens of the optical imaging system is denoted (exemplified) by NA 1; the refractive index of the first lens is denoted by Nd1 (for example).

Viewing angle-dependent lens parameters: the viewing angle is denoted AF; half of the viewing angle is denoted by HAF; the chief ray angle is denoted MRA.

Lens parameters related to entrance and exit pupils: the entrance pupil diameter of the optical imaging system is denoted by HEP; the maximum effective radius of any surface of a single lens refers to the vertical height between the intersection point (effective diameter) of the light rays of the incident light passing through the extreme edge of the entrance pupil at the maximum viewing angle of the system and the optical axis. For example, the maximum effective radius of the object-side surface of the first lens is indicated by EHD11 and the maximum effective radius of the image-side surface of the first lens is indicated by EHD 12. The maximum effective radius of the object-side surface of the second lens is indicated by EHD21 and the maximum effective radius of the image-side surface of the second lens is indicated by EHD 22. The maximum effective radius of any surface of the remaining lenses in the optical imaging system is expressed and so on.

Parameters related to lens profile depth: the horizontal displacement distance from the intersection point of the object-side surface of the fourth lens on the optical axis to the position of the maximum effective radius of the object-side surface of the fourth lens on the optical axis is shown (exemplified) by InRS 41; the horizontal displacement distance from the intersection point of the image side surface of the fourth lens on the optical axis to the maximum effective radius position of the image side surface of the fourth lens on the optical axis is shown by InRS42 (for example).

Parameters related to lens surface shape: the critical point C is a point on the surface of the particular lens that is tangent to a tangent plane perpendicular to the optical axis except for the intersection with the optical axis. For example, the perpendicular distance between the critical point C31 on the object-side surface of the third lens element and the optical axis is HVT31 (for example), the perpendicular distance between the critical point C32 on the image-side surface of the third lens element and the optical axis is HVT32 (for example), the perpendicular distance between the critical point C41 on the object-side surface of the fourth lens element and the optical axis is HVT41 (for example), and the perpendicular distance between the critical point C42 on the image-side surface of the fourth lens element and the optical axis is HVT42 (for example). The representation of the critical point on the object-side or image-side surface of the other lens and its perpendicular distance from the optical axis is comparable to the above.

The inflection point on the object-side surface of the fourth lens closest to the optical axis is IF411, the amount of this point depression is SGI411 (for example), SGI411 is the horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the fourth lens on the optical axis and the inflection point on the object-side surface of the fourth lens closest to the optical axis, and the vertical distance between this point of IF411 and the optical axis is HIF411 (for example). The inflection point on the image-side surface of the fourth lens closest to the optical axis is IF421, the amount of depression of the inflection point SGI421 (for example), SGI411 is the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the fourth lens on the optical axis and the inflection point on the image-side surface of the fourth lens closest to the optical axis, and the vertical distance between the point of the IF421 and the optical axis is HIF421 (for example).

The inflection point on the object-side surface of the fourth lens second closest to the optical axis is IF412, the amount of this point depression SGI412 (for example), SGI412 is the horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the fourth lens on the optical axis and the inflection point on the object-side surface of the fourth lens second closest to the optical axis, and the vertical distance between this point of IF412 and the optical axis is HIF412 (for example). The inflection point on the image-side surface of the fourth lens element second closest to the optical axis is IF422, the amount of this point depression SGI422 (for example), SGI422, i.e. the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the fourth lens element on the optical axis and the inflection point on the image-side surface of the fourth lens element second closest to the optical axis, and the vertical distance between this point of IF422 and the optical axis is HIF422 (for example).

The third inflection point on the object-side surface of the fourth lens near the optical axis is IF413, the depression amount SGI413 (for example) is the horizontal displacement distance parallel to the optical axis between SGI413, i.e., the intersection point of the object-side surface of the fourth lens on the optical axis, and the third inflection point on the object-side surface of the fourth lens near the optical axis, and the vertical distance between IF4132 and the optical axis is HIF413 (for example). The third inflection point on the image-side surface of the fourth lens near the optical axis is IF423, the depression amount SGI423 (for example) is a horizontal displacement distance parallel to the optical axis between the SGI423, that is, the intersection point of the image-side surface of the fourth lens on the optical axis and the third inflection point on the image-side surface of the fourth lens near the optical axis, and the vertical distance between the point of the IF423 and the optical axis is HIF423 (for example).

The fourth inflection point on the object-side surface of the fourth lens near the optical axis is IF414, the depression amount SGI414 (for example) is SGI414, i.e., the horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the fourth lens on the optical axis and the fourth inflection point on the object-side surface of the fourth lens near the optical axis, and the vertical distance between the point of IF414 and the optical axis is HIF414 (for example). The fourth inflection point on the image-side surface of the fourth lens element near the optical axis is IF424, the depression of the fourth inflection point is SGI424 (for example), SGI424 is the horizontal displacement distance parallel to the optical axis from the intersection point of the image-side surface of the fourth lens element on the optical axis to the fourth inflection point on the image-side surface of the fourth lens element near the optical axis, and the vertical distance between the point of IF424 and the optical axis is HIF424 (for example).

The representation of the inflection points on the object-side surface or the image-side surface of the other lens and the vertical distance between the inflection points and the optical axis or the amount of the depression of the inflection points is compared with the representation in the foregoing.

Aberration-related variables: optical Distortion (Optical Distortion) of an Optical imaging system is expressed in ODT; its TV Distortion (TV Distortion) is expressed in TDT and can further define the degree of aberration shift described between imaging 50% to 100% field of view; the spherical aberration offset is expressed as DFS; the coma aberration offset is denoted by DFC.

The Modulation Transfer Function (MTF) of the optical imaging system is used to test and evaluate the contrast and sharpness of the system image. The vertical axis of the modulation transfer function characteristic diagram represents the contrast ratio (value from 0 to 1), and the horizontal axis represents the spatial frequency (cycles/mm; lp/mm; line papers per mm). A perfect imaging system can theoretically present 100% of the line contrast of the subject, whereas a practical imaging system has a contrast transfer ratio value of less than 1 on the vertical axis. Furthermore, in general, the imaged edge regions may be more difficult to obtain a fine degree of reduction than the central region. In the visible spectrum, on the imaging plane, the contrast transfer rates (MTF values) of the optical axis, the field of view 0.3 and the field of view 0.7 at the spatial frequency of 55cycles/mm are respectively represented by MTFE0, MTFE3 and MTFE7, the contrast transfer rates (MTF values) of the optical axis, the field of view 0.3 and the field of view 0.7 at the spatial frequency of 110cycles/mm are respectively represented by MTFQ0, MTFQ3 and MTFQ7, the contrast transfer rates (MTF values) of the optical axis, the field of view 0.3 and the field of view 0.7 at the spatial frequency of 220cycles/mm are respectively represented by MTFH0, MTFH3 and MTFH7, and the contrast transfer rates (MTF values) of the optical axis, the field of view 0.3 and the field of view 0.7 at the spatial frequency of 440cycles/mm are respectively represented by MTF0, MTF3 and MTF7, and the three fields have respective MTF values for the center, the lens, the inner field and the representative of the optical performance of the particular imaging system. If the optical imaging system is designed to correspond to a photosensitive element with a Pixel Size (Pixel Size) of less than 1.12 μm, the quarter spatial frequency, half spatial frequency (half frequency) and full spatial frequency (full frequency) of the modulation transfer function characteristic map are at least 110cycles/mm, 220cycles/mm and 440cycles/mm, respectively.

If the optical imaging system needs to meet the imaging requirements for the infrared spectrum, such as night vision requirements for low-light sources, the used operating wavelength can be 850nm or 800nm, and since the main function is to identify the object contour formed by black and white light and shade, high resolution is not required, it is only necessary to select a spatial frequency less than 110cycles/mm to evaluate whether the performance of the specific optical imaging system in the infrared spectrum is excellent. When the operating wavelength is 850nm and the image is focused on the image plane, the contrast transfer ratios (MTF values) of the image at the spatial frequency of 55cycles/mm in the optical axis, 0.3 field and 0.7 field are respectively expressed by MTFI0, MTFI3 and MTFI 7. However, since the difference between the infrared operating wavelength of 850nm or 800nm and the common visible light wavelength is very large, it is difficult to design the optical imaging system to focus on both visible light and infrared (dual mode) and achieve certain performance.

An optical imaging system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element and a fourth lens element with refractive power. The optical imaging system further comprises an image sensing element disposed on the imaging surface.

The optical imaging system can be designed using three operating wavelengths, 486.1nm, 587.5nm, and 656.2nm, respectively, where 587.5nm is the primary reference wavelength for the primary extraction feature. The optical imaging system can also be designed using five operating wavelengths, 470nm, 510nm, 555nm, 610nm and 650nm, respectively, where 555nm is the primary reference wavelength for the primary extraction features.

The ratio PPR of the focal length f of the optical imaging system to the focal length fp of each lens with positive refractive power, the ratio NPR of the focal length f of the optical imaging system to the focal length fn of each lens with negative refractive power, the sum of the PPRs of all the lenses with positive refractive power is Σ PPR, and the sum of the NPRs of all the lenses with negative refractive power is Σ NPR, which is helpful to control the total refractive power and the total length of the optical imaging system when the following conditions are satisfied: 0.5 ≦ Σ PPR/| Σ NPR ≦ 4.5, preferably, the following condition may be satisfied: 1 ≦ Σ PPR/| Σ NPR | < 3.5.

The optical imaging system has a HOS system height, and when the HOS/f ratio approaches 1, the optical imaging system which is miniaturized and can image ultra-high pixels is facilitated to be manufactured.

The total sum fp of the focal length of each lens with positive refractive power of the optical imaging system is Σ PP, and the total sum of the focal length of each lens with negative refractive power is Σ NP, the utility model discloses an embodiment of the optical imaging system, it satisfies the following condition: 0< sigma PP is less than or equal to 200; and f 1/Sigma PP is less than or equal to 0.85. Preferably, the following conditions may be satisfied: 0< sigma PP is less than or equal to 150; and f 1/Sigma PP is more than or equal to 0.01 and less than or equal to 0.7. Thereby, it is helpful to control the focusing power of the optical imaging system and to properly distribute the positive refractive power of the system to suppress the premature generation of significant aberrations.

The first lens element with positive refractive power has a convex object-side surface. Therefore, the positive refractive power strength of the first lens element can be properly adjusted, which is beneficial to shortening the total track length of the optical imaging system.

The second lens element has negative refractive power. Thus, aberration generated by the first lens can be corrected.

The third lens element can have positive refractive power. Therefore, the positive refractive power of the first lens element can be shared.

The fourth lens element with negative refractive power has a concave image-side surface. Thereby, it is advantageous to shorten the back focal length to maintain miniaturization. In addition, at least one surface of the fourth lens element can have at least one point of inflection, which can effectively suppress the incident angle of the light in the off-axis field of view, and further correct the aberration in the off-axis field of view. Preferably, the object side and the image side of the image sensor have at least one inflection point.

The optical imaging system may further include an image sensor disposed on the imaging surface. Half of the diagonal length of the effective sensing area of the image sensor (i.e. the imaging height of the optical imaging system or the maximum image height) is HOI, and the distance from the object-side surface of the first lens to the imaging surface on the optical axis is HOS, which satisfies the following conditions: HOS/HOI is less than or equal to 3; and HOS/f is more than or equal to 0.5 and less than or equal to 3.0. Preferably, the following conditions may be satisfied: HOS/HOI is more than or equal to 1 and less than or equal to 2.5; and HOS/f is more than or equal to 1 and less than or equal to 2. Therefore, the optical imaging system can be kept small and can be mounted on light and thin portable electronic products.

Additionally, the utility model discloses an among the optical imaging system, can set up an at least light ring according to the demand to reduce stray light, help promoting image quality.

The utility model discloses an among the optical imaging system, the diaphragm configuration can be leading light ring or put the light ring, and wherein leading light ring meaning light ring sets up between shot object and first lens promptly, and the middle-placed light ring then shows that the light ring sets up between first lens and imaging surface. If the diaphragm is a front diaphragm, the exit pupil of the optical imaging system can generate a longer distance with the imaging surface to accommodate more optical elements, and the image receiving efficiency of the image sensing element can be increased; if the aperture is located in the middle, it is helpful to enlarge the field angle of the system, so that the optical imaging system has the advantage of wide-angle lens. The distance between the diaphragm and the imaging surface is InS, which satisfies the following condition: 0.2-1.1 of InS/HOS. Preferably, the following conditions may be satisfied: 0.8. ltoreq. InS/HOS. ltoreq.1, thereby maintaining both miniaturization of the optical imaging system and wide-angle characteristics.

The utility model discloses an among the optical imaging system, the distance between first lens body side to fourth lens image side is the InTL, and in the thickness sum sigma TP of all lens that have refractive power on the optical axis, it satisfies the following condition: the Sigma TP/InTL ratio is more than or equal to 0.45 and less than or equal to 0.95. Preferably, the following conditions may be satisfied: sigma TP/InTL is more than or equal to 0.6 and less than or equal to 0.9. Therefore, the contrast of system imaging and the yield of lens manufacturing can be considered simultaneously, and a proper back focus is provided for accommodating other elements.

The radius of curvature of the object-side surface of the first lens is R1, and the radius of curvature of the image-side surface of the first lens is R2, which satisfies the following conditions: the | R1/R2 | is not less than 0.01 and not more than 0.5. Therefore, the first lens element has proper positive refractive power strength, and the spherical aberration is prevented from increasing and speeding up. Preferably, the following conditions may be satisfied: the | R1/R2 | is not less than 0.01 and not more than 0.4.

The radius of curvature of the object-side surface of the fourth lens is R7, and the radius of curvature of the image-side surface of the fourth lens is R8, which satisfies the following conditions: -200< (R7-R8)/(R7+ R8) < 30. Thereby, astigmatism generated by the optical imaging system is favorably corrected.

The first lens and the second lens are separated by a distance IN12 on the optical axis, which satisfies the following condition: 0< IN12/f is less than or equal to 0.25. Preferably, the following conditions may be satisfied: IN12/f is more than or equal to 0.01 and less than or equal to 0.20. Therefore, the chromatic aberration of the lens is improved to improve the performance of the lens.

The second lens and the third lens are separated by a distance IN23 on the optical axis, which satisfies the following condition: 0< IN23/f is less than or equal to 0.25. Preferably, the following conditions may be satisfied: IN23/f is more than or equal to 0.01 and less than or equal to 0.20. Thereby contributing to improved lens performance.

The third lens element and the fourth lens element are separated by a distance IN34 on the optical axis, which satisfies the following condition: 0< IN34/f is less than or equal to 5. Preferably, the following conditions may be satisfied: IN34/f is more than or equal to 0.001 and less than or equal to 0.20. Thereby contributing to improved lens performance.

The thicknesses of the first lens element and the second lens element on the optical axis are TP1 and TP2, respectively, which satisfy the following conditions: (TP1+ IN12)/TP2 is more than or equal to 1 and less than or equal to 10. Thereby, it is helpful to control the sensitivity of the optical imaging system and improve its performance.

The thicknesses of the third lens element and the fourth lens element on the optical axis are TP3 and TP4, respectively, and the distance between the two lens elements on the optical axis is IN34, which satisfies the following conditions: (TP4+ IN34)/TP4 is not more than 0.2 and not more than 3. Thereby, it is helpful to control the sensitivity of the optical imaging system manufacturing and reduce the total system height.

The distance between the second lens element and the third lens element is IN23, and the total distance between the first lens element and the fourth lens element is Σ TP, which satisfies the following conditions: IN23/(TP2+ IN23+ TP3) is not less than 0.01 but not more than 0.5. Preferably, the following conditions may be satisfied: IN23/(TP2+ IN23+ TP3) is not less than 0.05 but not more than 0.4. Thereby helping to slightly correct the aberration generated during the incident light traveling process and reducing the total height of the system.

The utility model discloses an among the optical imaging system, the horizontal displacement distance that fourth lens object side 142 was placed in the optical axis at the point of intersection on the optical axis to the maximum effective radius position of fourth lens object side 142 is InRS41 (if horizontal displacement is towards the image side, InRS41 is the positive value; if horizontal displacement is towards the thing side, InRS41 is the negative value), the horizontal displacement distance that fourth lens image side 144 was placed in the optical axis at the point of intersection on the optical axis to the maximum effective radius position of fourth lens image side 144 is InRS42, fourth lens 140 is TP4 in the epaxial thickness of optical axis, it satisfies following condition: -1 mm. ltoreq. InRS 41. ltoreq.1 mm; -1 mm. ltoreq. InRS 42. ltoreq.1 mm; more than or equal to 1mm | InRS41 | + | InRS42 | is less than or equal to 2 mm; 0.01-10 of InRS 41/TP 4; 0.01-InRS 42-TP 4-10. Therefore, the maximum effective radius position between the two surfaces of the fourth lens can be controlled, thereby being beneficial to aberration correction of the peripheral field of view of the optical imaging system and effectively maintaining miniaturization of the optical imaging system.

The utility model discloses an among the optical imaging system, fourth lens object side represents with SGI411 with the parallel horizontal displacement distance of optical axis between the point of inflection of the most recent optical axis of the nodical of optical axis to fourth lens object side, and fourth lens image side represents with SGI421 with the parallel horizontal displacement distance of optical axis between the point of inflection of the most recent optical axis of the nodical of optical axis to fourth lens image side, and it satisfies the following condition: 0< SGI411/(SGI411+ TP4) < 0.9; 0< SGI421/(SGI421+ TP4) ≦ 0.9. Preferably, the following conditions may be satisfied: 0.01< SGI411/(SGI411+ TP4) < 0.7; 0.01< SGI421/(SGI421+ TP4) ≦ 0.7.

A horizontal displacement distance parallel to the optical axis between an intersection point of the object-side surface of the fourth lens element on the optical axis and an inflection point of the object-side surface of the fourth lens element second near the optical axis is represented by SGI412, and a horizontal displacement distance parallel to the optical axis between an intersection point of the image-side surface of the fourth lens element on the optical axis and an inflection point of the image-side surface of the fourth lens element second near the optical axis is represented by SGI422, which satisfies the following conditions: 0< SGI412/(SGI412+ TP4) ≦ 0.9; 0< SGI422/(SGI422+ TP4) ≦ 0.9. Preferably, the following conditions may be satisfied: SGI412/(SGI412+ TP4) is more than or equal to 0.1 and less than or equal to 0.8; SGI422/(SGI422+ TP4) is more than or equal to 0.1 and less than or equal to 0.8.

The vertical distance between the inflection point of the nearest optical axis of the object side surface of the fourth lens and the optical axis is represented by HIF411, the vertical distance between the inflection point of the nearest optical axis of the image side surface of the fourth lens and the optical axis from the intersection point of the image side surface of the fourth lens on the optical axis to the image side surface of the fourth lens is represented by HIF421, and the following conditions are satisfied: HIF411/HOI is more than or equal to 0.01 and less than or equal to 0.9; HIF421/HOI is more than or equal to 0.01 and less than or equal to 0.9. Preferably, the following conditions may be satisfied: HIF411/HOI is more than or equal to 0.09 and less than or equal to 0.5; HIF421/HOI is more than or equal to 0.09 and less than or equal to 0.5.

The vertical distance between the second near-optic axis inflection point of the object-side surface of the fourth lens and the optical axis is denoted by HIF412, and the vertical distance between the second near-optic axis inflection point of the image-side surface of the fourth lens and the optical axis from the intersection point of the image-side surface of the fourth lens and the optical axis is denoted by HIF422, wherein the following conditions are satisfied: HIF412/HOI 0.01 ≤ 0.9; HIF422/HOI is not less than 0.01 but not more than 0.9. Preferably, the following conditions may be satisfied: HIF412/HOI is more than or equal to 0.09 and less than or equal to 0.8; HIF422/HOI is more than or equal to 0.09 and less than or equal to 0.8.

The vertical distance between the third inflection point near the optical axis of the object-side surface of the fourth lens and the optical axis is represented by HIF413, and the vertical distance between the intersection point on the optical axis of the image-side surface of the fourth lens and the third inflection point near the optical axis and the optical axis is represented by HIF423, which satisfies the following conditions: 0.001mm ≦ HIF413 ≦ 5 mm; 0.001mm ≦ HIF423 ≦ 5 mm. Preferably, the following conditions may be satisfied: 0.1mm < l HIF423 > 3.5 mm; and | HIF413 | of 0.1mm is less than or equal to 3.5 mm.

The vertical distance between the fourth inflection point near the optical axis of the object-side surface of the fourth lens and the optical axis is represented by HIF414, and the vertical distance between the fourth inflection point near the optical axis and the optical axis from the intersection point on the optical axis of the image-side surface of the fourth lens to the image-side surface of the fourth lens is represented by HIF424, wherein the following conditions are satisfied: 0.001mm ≦ HIF414 ≦ 5 mm; 0.001mm ≦ HIF424 ≦ 5 mm. Preferably, the following conditions may be satisfied: 0.1mm ≦ HIF424 ≦ 3.5 mm; 0.1mm ≦ HIF414 ≦ 3.5 mm.

The utility model discloses an optical imaging system's an embodiment, the accessible has the lens staggered arrangement of high dispersion coefficient and low dispersion coefficient to help optical imaging system chromatic aberration's correction.

The equation for the aspheric surface is:

z＝ch²/[1+[1-(k+1)c²h²]^0.5]+A4h⁴+A6h⁶+A8h⁸+A10h¹⁰+A12h¹²+A14h¹⁴+A16h¹⁶+A18h¹⁸+A20h²⁰+… (1)

where z is a position value referenced to a surface vertex at a position of height h in the optical axis direction, k is a cone coefficient, c is an inverse of a curvature radius, and a4, a6, A8, a10, a12, a14, a16, a18, and a20 are high-order aspheric coefficients.

The utility model provides an among the optical imaging system, the material of lens can be plastic or glass. When the lens is made of plastic, the production cost and the weight can be effectively reduced. In addition, when the lens is made of glass, the thermal effect can be controlled and the design space for the refractive power configuration of the optical imaging system can be increased. In addition, the object side and the image side of first lens to fourth lens among the optical imaging system can be the aspheric surface, and it can obtain more control variable, except that being used for subducing the aberration, compare in the use of traditional glass lens and can reduce the number that the lens used even, consequently can effectively reduce the utility model discloses optical imaging system's overall height.

Furthermore, in the optical imaging system provided by the present invention, if the lens surface is convex, it means that the lens surface is convex at the position close to the optical axis; if the lens surface is concave, it means that the lens surface is concave at a paraxial region.

Additionally, the utility model discloses an among the optical imaging system, can set up an at least diaphragm according to the demand to reduce stray light, help promoting image quality.

The utility model discloses an optical imaging system more visual demand is applied to in the optical system that removes and focus to have good aberration concurrently and revise and good imaging quality's characteristic, thereby enlarge the application aspect.

The utility model discloses a more visual demand of optical imaging system includes a drive module, and this drive module can be coupled with these some lenses and make these some lenses produce the displacement. The driving module may be a Voice Coil Motor (VCM) for driving the lens to focus, or an optical anti-shake element (OIS) for reducing the frequency of out-of-focus caused by lens vibration during the shooting process.

The utility model discloses a more visual demand of optical imaging system makes at least one lens be the light filtering component that the wavelength is less than 500nm in first lens, second lens, third lens, the fourth lens, and the coating film on at least one surface of the lens of its accessible this special utensil filtering function or this lens itself are made by the material that has the filterable short wavelength and reach promptly.

The utility model discloses a more visual demand of imaging surface of optical imaging system selects to a plane or a curved surface. The imaging plane is a curved surface (e.g., a spherical surface with a radius of curvature), which helps to reduce the incident angle required for focusing light on the imaging plane, and besides helps to achieve the length (TTL) of the miniature optical imaging system, it is also beneficial to increase the relative illumination.

In the following, specific embodiments are provided and will be described in detail with reference to the drawings.

First embodiment

Referring to fig. 1 to fig. 3, wherein fig. 1 is a schematic diagram illustrating an optical imaging system according to a first embodiment of the present invention, and fig. 2 is a graph illustrating spherical aberration, astigmatism and optical distortion of the optical imaging system according to the first embodiment in order from left to right. Fig. 3 is a diagram of a visible light modulation conversion characteristic of the optical imaging system of the first embodiment. In fig. 1, the optical imaging system 10 includes, in order from an object side to an image side, an aperture stop 100, a first lens element 110, a second lens element 120, a third lens element 130, a fourth lens element 140, an ir-filter 170, an image plane 180, and an image sensor 190.

The first lens element 110 with positive refractive power has a convex object-side surface 112 and a concave image-side surface 114, and is aspheric, and the object-side surface 112 and the image-side surface 114 both have inflection points. The thickness of the first lens on the optical axis is TP1, and the thickness of the first lens at 1/2 entrance pupil diameter (HEP) height is indicated as ETP 1.

The horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the first lens on the optical axis and the inflection point of the nearest optical axis of the object-side surface of the first lens is represented by SGI111, and the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the first lens on the optical axis and the inflection point of the nearest optical axis of the image-side surface of the first lens is represented by SGI121, which satisfies the following conditions: SGI 111-0.2008 mm; SGI121 ═ 0.0113 mm; -SGI 111 |/(| SGI111 | + TP1) | -0.3018; | SGI121 |/(| SGI121 | + TP1) | 0.0238.

The vertical distance between the optical axis and the inflection point of the optical axis intersection point of the object-side surface of the first lens element to the nearest optical axis of the object-side surface of the first lens element is represented by HIF111, and the vertical distance between the optical axis and the inflection point of the optical axis intersection point of the image-side surface of the first lens element to the nearest optical axis of the image-side surface of the first lens element is represented by HIF121, which satisfies the following conditions: HIF 111-0.7488 mm; HIF 121-0.4451 mm; HIF111/HOI 0.2552; HIF121/HOI 0.1517.

The second lens element 120 with positive refractive power has a concave object-side surface 122 and a convex image-side surface 124, and is aspheric, and the object-side surface 122 has an inflection point. The thickness of the second lens on the optical axis is TP2, and the thickness of the second lens at 1/2 entrance pupil diameter (HEP) height is indicated as ETP 2.

The horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the second lens on the optical axis and the inflection point of the nearest optical axis of the object-side surface of the second lens is represented by SGI211, and the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the second lens on the optical axis and the inflection point of the nearest optical axis of the image-side surface of the second lens is represented by SGI221, which satisfies the following conditions: SGI211 ═ -0.1791 mm; | SGI211 |/(| SGI211 | + TP2) | -0.3109.

The vertical distance between the optical axis and the inflection point of the optical axis of the object-side surface of the second lens element from the optical axis to the nearest optical axis of the object-side surface of the second lens element is represented by HIF211, and the vertical distance between the optical axis and the inflection point of the optical axis from the optical axis of the image-side surface of the second lens element from the nearest optical axis of the image-side surface of the second lens element is represented by HIF221, which satisfies the following conditions: HIF 211-0.8147 mm; HIF211/HOI 0.2777.

The third lens element 130 with negative refractive power has a concave object-side surface 132 and a convex image-side surface 134, and is aspheric, and the image-side surface 134 has an inflection point. The thickness of the third lens on the optical axis is TP3, and the thickness of the third lens at 1/2 entrance pupil diameter (HEP) height is represented by ETP 3.

The horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the third lens on the optical axis and the inflection point of the nearest optical axis of the object-side surface of the third lens is represented by SGI311, and the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the third lens on the optical axis and the inflection point of the nearest optical axis of the image-side surface of the third lens is represented by SGI321, which satisfies the following conditions: SGI 321-0.1647 mm; -SGI 321 |/(| SGI321 | + TP3) — 0.1884.

The vertical distance between the inflection point of the nearest optical axis of the object-side surface of the third lens and the optical axis is represented by HIF311, the vertical distance between the inflection point of the nearest optical axis of the image-side surface of the third lens and the optical axis is represented by HIF321, and the following conditions are satisfied: HIF 321-0.7269 mm; HIF321/HOI 0.2477.

The fourth lens element 140 with negative refractive power has a convex object-side surface 142 and a concave image-side surface 144, and is aspheric, wherein the object-side surface 142 has two inflection points and the image-side surface 144 has one inflection point. The thickness of the fourth lens on the optical axis is TP4, and the thickness of the fourth lens at 1/2 entrance pupil diameter (HEP) height is indicated as ETP 4.

The horizontal displacement distance parallel to the optical axis between the intersection point of the object-side surface of the fourth lens on the optical axis and the inflection point of the nearest optical axis of the object-side surface of the fourth lens is represented by SGI411, and the horizontal displacement distance parallel to the optical axis between the intersection point of the image-side surface of the fourth lens on the optical axis and the inflection point of the nearest optical axis of the image-side surface of the fourth lens is represented by SGI421, which satisfies the following conditions: SGI411 ═ 0.0137 mm; SGI421 ═ 0.0922 mm; -SGI 411 |/(| SGI411 | + TP4) ═ 0.0155; | SGI421 |/(| SGI421 | + TP4) | -0.0956.

A horizontal displacement distance parallel to the optical axis between an intersection of the object-side surface of the fourth lens element on the optical axis to a second inflection point of the object-side surface of the fourth lens element adjacent to the optical axis is denoted by SGI412, which satisfies the following condition: SGI412 ═ -0.1518 mm; | SGI412 |/(| SGI412 | + TP4) | -0.1482.

The vertical distance between the inflection point of the nearest optical axis of the object-side surface of the fourth lens and the optical axis is represented by HIF411, and the vertical distance between the inflection point of the nearest optical axis of the image-side surface of the fourth lens and the optical axis is represented by HIF411, which satisfies the following conditions: HIF411 mm 0.2890 mm; HIF421 of 0.5794 mm; HIF411/HOI ═ 0.0985; HIF421/HOI 0.1975.

The vertical distance between the inflection point of the second paraxial region of the object-side surface of the fourth lens and the optical axis is denoted by HIF412, which satisfies the following conditions: HIF412 ═ 1.3328 mm; HIF412/HOI 0.4543.

The distance parallel to the optical axis between the coordinate point at the height of 1/2HEP on the object-side surface of the first lens element and the image plane is ETL, and the horizontal distance parallel to the optical axis between the coordinate point at the height of 1/2HEP on the object-side surface of the first lens element and the coordinate point at the height of 1/2HEP on the image-side surface of the fourth lens element is EIN, which satisfies the following conditions: ETL 18.744 mm; EIN 12.339 mm; EIN/ETL is 0.658.

This example satisfies the following condition, ETP1 ═ 0.949 mm; ETP2 ═ 2.483 mm; ETP3 ═ 0.345 mm; ETP4 ═ 1.168 mm. The sum SETP of the ETP1 to ETP4 is 4.945 mm. TP1 ═ 0.918 mm; TP2 ═ 2.500 mm; TP3 ═ 0.300 mm; TP4 ═ 1.248 mm; the sum STP of the aforementioned TP1 to TP4 is 4.966 mm; SETP/STP is 0.996; SETP/EIN 0.40076.

In the present embodiment, the proportional relationship (ETP/TP) between the thickness (ETP) of each lens at the height of the entrance pupil diameter (HEP) of 1/2 and the Thickness (TP) of the lens on the optical axis to which the surface belongs is controlled in order to balance manufacturability and aberration correction capability, which satisfies the following condition, ETP1/TP1 is 1.034; ETP2/TP2 ═ 0.993; ETP3/TP3 ═ 1.148; ETP4/TP4 is 0.936.

IN the present embodiment, the horizontal distance between two adjacent lenses at the height of 1/2 entrance pupil diameter (HEP) is controlled to balance the length HOS "shrinkage" degree of the optical imaging system, the manufacturability and the aberration correction capability, and particularly, the proportional relationship (ED/IN) between the horizontal distance (ED) between the height of 1/2 entrance pupil diameter (HEP) of the two adjacent lenses and the horizontal distance (IN) between the two adjacent lenses on the optical axis is controlled to satisfy the following condition, and the horizontal distance parallel to the optical axis between the first lens and the second lens at the height of 1/2 entrance pupil diameter (HEP) is ED12 ═ 4.529 mm; the horizontal distance parallel to the optical axis between the second lens and the third lens at the height of 1/2 entrance pupil diameter (HEP) is ED 23-2.735 mm; the horizontal distance parallel to the optical axis between the third lens and the fourth lens at the height of 1/2 entrance pupil diameter (HEP) is ED34 ═ 0.131 mm.

The horizontal distance between the first lens and the second lens on the optical axis is IN 12-4.571 mm, and the ratio between the two is ED12/IN 12-0.991. The horizontal distance between the second lens and the third lens on the optical axis is IN 23-2.752 mm, and the ratio between the two is ED23/IN 23-0.994. The horizontal distance between the third lens and the fourth lens on the optical axis is IN 34-0.094 mm, and the ratio between the two is ED34/IN 34-1.387.

The horizontal distance that is on a parallel with the optical axis between the coordinate point of 1/2HEP height on the fourth lens looks like the side to this image plane is EBL 6.405mm, on the fourth lens looks like the side with the crossing point of optical axis to this image plane between the horizontal distance that is on a parallel with the optical axis be BL 6.3642mm, the embodiment of the utility model can satisfy the following formula: and EBL/BL is 1.00641. In this embodiment, the distance between the coordinate point of the 1/2HEP height on the image-side surface of the fourth lens element and the infrared filter, which is parallel to the optical axis, is EIR 0.065mm, and the distance between the intersection point of the image-side surface of the fourth lens element and the optical axis and the infrared filter, which is parallel to the optical axis, is PIR 0.025mm, and the following formula is satisfied: EIR/PIR 2.631.

The infrared filter 170 is made of glass, and is disposed between the fourth lens element 140 and the image plane 180 without affecting the focal length of the optical imaging system.

In the optical imaging system of the first embodiment, the focal length of the optical imaging system is f, the entrance pupil diameter of the optical imaging system is HEP, and half of the maximum angle of view in the optical imaging system is HAF, which has the following values: 3.4375 mm; f/HEP is 2.23; and HAF 39.69 degrees and tan (HAF) 0.8299.

In the optical imaging system of the first embodiment, the focal length of the first lens 110 is f1, and the focal length of the fourth lens 140 is f4, which satisfies the following conditions: f1 is 3.2736 mm; | f/f1 | -1.0501; f 4-8.3381 mm; and | f1/f4 | -0.3926; f1/f 4-0.39261.

In the optical imaging system of the first embodiment, the focal lengths of the second lens 120 to the third lens 130 are f2 and f3, respectively, which satisfy the following conditions: | f2 | + -f 3 | -10.0976 mm; | f1 | + | f4 | _ 11.6116mm and | f2 | + f3 | f1 | + | f4 |.

In the optical imaging system of the first embodiment, the sum of the PPRs of all the lenses with positive refractive power is Σ PPR | f/f1 | + | f/f2 | -1.95585, and the sum of the NPRs of all the lenses with negative refractive power is Σ NPR | -f/f 3 | + | f/f4 | -0.95770, and Σ PPR/| NPR | -2.04224. The following conditions are also satisfied: | f/f1 | -1.05009; | f/f2 | -0.90576; | f/f3 | -0.54543; | f/f4 | -0.41227; f2/f 3-0.60219.

In the optical imaging system of the first embodiment, a distance between the object-side surface 112 of the first lens element and the image-side surface 144 of the fourth lens element is InTL, a distance between the object-side surface 112 of the first lens element and the image plane 180 of the first lens element is HOS, a distance between the aperture stop 100 and the image plane 180 of the first lens element is InS, a half of a diagonal length of an effective sensing area of the image sensor 190 is HOI, and a distance between the image-side surface 144 of the fourth lens element and the image plane 180 of the fourth lens element is InB, which satisfies the following conditions: instl + InB ═ HOS; HOS 4.4250 mm; HOI 2.9340 mm; HOS/HOI 1.5082; HOS/f 1.2873; 0.7191 for InTL/HOS; 4.2128mm for InS; and InS/HOS 0.95204.

In the optical imaging system of the first embodiment, the sum of the thicknesses of all the lenses with refractive power on the optical axis is Σ TP, which satisfies the following condition: Σ TP is 2.4437 mm; and Σ TP/intil 0.76793. Therefore, the contrast of system imaging and the yield of lens manufacturing can be considered simultaneously, and a proper back focus is provided for accommodating other elements.

In the optical imaging system of the first embodiment, the radius of curvature of the object-side surface 112 of the first lens is R1, and the radius of curvature of the image-side surface 114 of the first lens is R2, which satisfies the following conditions: R1/R2 | -0.1853. Therefore, the first lens element has proper positive refractive power strength, and the spherical aberration is prevented from increasing and speeding up.

In the optical imaging system of the first embodiment, the radius of curvature of the object-side surface 142 of the fourth lens is R7, and the radius of curvature of the image-side surface 144 of the fourth lens is R8, which satisfies the following conditions: (R7-R8)/(R7+ R8) ═ 0.2756. Thereby, astigmatism generated by the optical imaging system is favorably corrected.

In the optical imaging system of the first embodiment, the respective focal lengths of the first lens element 110 and the second lens element 120 are f1 and f2, respectively, and the sum of the focal lengths of all the lens elements with positive refractive power is Σ PP, which satisfies the following condition: f1+ f2 is 7.0688 mm; and f1/(f1+ f2) ═ 0.4631. Therefore, the positive refractive power of the first lens element 110 can be properly distributed to other positive lens elements, so as to suppress the occurrence of significant aberration during the incident light traveling process.

In the optical imaging system of the first embodiment, the respective focal lengths of the third lens element 130 and the fourth lens element 140 are f3 and f4, respectively, and the sum of the focal lengths of all the lens elements with negative refractive power is Σ NP, which satisfies the following condition: Σ NP ═ f3+ f4 ═ -14.6405 mm; and f4/(f2+ f4) ═ 0.5695. Therefore, the negative refractive power of the fourth lens element can be properly distributed to the other negative lens elements, so as to suppress the generation of significant aberration during the incident light traveling process.

IN the optical imaging system of the first embodiment, the first lens element 110 and the second lens element 120 are separated by an optical axis distance IN12, which satisfies the following condition: IN 12-0.3817 mm; IN12/f 0.11105. Therefore, the chromatic aberration of the lens is improved to improve the performance of the lens.

IN the optical imaging system of the first embodiment, the second lens element 120 and the third lens element 130 are separated by an optical axis distance IN23, which satisfies the following condition: IN 23-0.0704 mm; IN23/f 0.02048. Therefore, the chromatic aberration of the lens is improved to improve the performance of the lens.

IN the optical imaging system of the first embodiment, the third lens 130 and the fourth lens 140 are separated by an optical axis distance IN34, which satisfies the following condition: IN 34-0.2863 mm; IN34/f 0.08330. Therefore, the chromatic aberration of the lens is improved to improve the performance of the lens.

In the optical imaging system of the first embodiment, the thicknesses of the first lens element 110 and the second lens element 120 on the optical axis are TP1 and TP2, respectively, which satisfy the following conditions: TP 1-0.46442 mm; TP 2-0.39686 mm; TP1/TP2 ═ 1.17023 and (TP1+ IN12)/TP2 ═ 2.13213. Thereby, it is helpful to control the sensitivity of the optical imaging system and improve its performance.

IN the optical imaging system of the first embodiment, the thicknesses of the third lens element 130 and the fourth lens element 140 on the optical axis are TP3 and TP4, respectively, and the distance between the two lens elements on the optical axis is IN34, which satisfies the following conditions: TP 3-0.70989 mm; TP 4-0.87253 mm; TP3/TP4 ═ 0.81359; TP2/TP3 ═ 0.5591; and (TP4+ IN34)/TP3 ═ 1.63248. Thereby, it is helpful to control the sensitivity of the optical imaging system manufacturing and reduce the total system height.

In the optical imaging system of the first embodiment, the following conditions are satisfied: IN23/(TP2+ IN23+ TP3) 0.05980. Thereby helping to slightly correct the aberration generated during the incident light traveling process and reducing the total height of the system.

In the optical imaging system of the first embodiment, a horizontal displacement distance between an intersection point of the fourth lens object-side surface 142 on the optical axis and a maximum effective radius position of the fourth lens object-side surface 142 on the optical axis is InRS41, a horizontal displacement distance between an intersection point of the fourth lens image-side surface 144 on the optical axis and a maximum effective radius position of the fourth lens image-side surface 144 on the optical axis is InRS42, and a thickness of the fourth lens 140 on the optical axis is TP4, which satisfies the following conditions: InRS 41-0.23761 mm; InRS 42-0.20206 mm; | InRS41 | + | InRS42 | 0.43967 mm; | InRS41 |/TP 4 ═ 0.27232; and | InRS42 |/TP 4 ═ 0.23158. Therefore, the lens is beneficial to manufacturing and molding and effectively maintains the miniaturization of the lens.

In the optical imaging system of the present embodiment, the perpendicular distance between the critical point C41 of the object-side surface 142 of the fourth lens element and the optical axis is HVT41, and the perpendicular distance between the critical point C42 of the image-side surface 144 of the fourth lens element and the optical axis is HVT42, which satisfies the following conditions: HVT41 ═ 0.5695 mm; HVT42 ═ 1.3556 mm; HVT41/HVT 42-0.4201. Therefore, the aberration of the off-axis field can be effectively corrected.

The optical imaging system of the embodiment satisfies the following conditions: HVT42/HOI 0.4620. Thereby, aberration correction of the peripheral field of view of the optical imaging system is facilitated.

The optical imaging system of the embodiment satisfies the following conditions: HVT42/HOS 0.3063. Thereby, aberration correction of the peripheral field of view of the optical imaging system is facilitated.

In the optical imaging system of the first embodiment, the first lens has an abbe number NA1, the second lens has an abbe number NA2, the third lens has an abbe number NA3, and the fourth lens has an abbe number NA4, and the following conditions are satisfied: -NA 1-NA 2-0; NA3/NA2 0.39921. This contributes to correction of chromatic aberration of the optical imaging system.

In the optical imaging system of the first embodiment, the TV distortion at the time of image formation of the optical imaging system is TDT, and the optical distortion at the time of image formation is ODT, which satisfy the following conditions: | TDT | -0.4%; and | ODT | -2.5%.

In the optical imaging system of the present embodiment, the modulation conversion contrast transfer ratios (MTF values) at half frequency of the optical axis, 0.3HOI and 0.7HOI on the imaging plane are respectively expressed by MTFH0, MTFH3 and MTFH7, which satisfy the following conditions: MTFH0 was about 0.525; MTFH3 was about 0.375; and MTFH7 was about 0.35.

The imaging height of the optical imaging system is HOI, and the optical axis, 0.3HOI and 0.7HOI of visible light on the imaging surface are respectively represented by MTFE0, MTFE3 and MTFE7 at a spatial frequency of 55cycles/mm, which satisfy the following conditions: MTFE0 was about 0.89; MTFE3 was about 0.88; and MTFE7 is about 0.85.

The imaging height of the optical imaging system is HOI, and the optical axis of visible light on the imaging surface, 0.3HOI and 0.7HOI are respectively represented by MTFQ0, MTFQ3 and MTFQ7 at a spatial frequency of 110cycles/mm, which satisfy the following conditions: MTFQ0 was about 0.74; MTFQ3 was about 0.68; and MTFQ7 is about 0.62.

The following list I and list II are referred to cooperatively.

TABLE II aspherical coefficients of the first example

The first embodiment is a detailed structural data of the first embodiment, wherein the unit of the radius of curvature, the thickness, the distance, and the focal length is mm, and the surfaces 0-14 sequentially represent the surfaces from the object side to the image side. Table II shows aspheric data of the first embodiment, where k represents the cone coefficients in the aspheric curve equation, and A1-A20 represents the aspheric coefficients of order 1-20 of each surface. In addition, the following tables of the embodiments correspond to the schematic diagrams and aberration graphs of the embodiments, and the definitions of the data in the tables are the same as those of the first and second tables of the first embodiment, which is not repeated herein.

Second embodiment

Referring to fig. 4 to 6, wherein fig. 4 is a schematic view illustrating an optical imaging system according to a second embodiment of the present invention, and fig. 5 is a graph illustrating spherical aberration, astigmatism and optical distortion of the optical imaging system according to the second embodiment in order from left to right. Fig. 6 is a diagram showing a visible spectrum modulation conversion characteristic of the optical imaging system of the second embodiment. In fig. 4, the optical imaging system 20 includes, in order from an object side to an image side, a first lens element 210, an aperture stop 200, a second lens element 220, a third lens element 230, a fourth lens element 240, an ir-filter 270, an image plane 280 and an image sensor 290.

The first lens element 210 with negative refractive power has a concave object-side surface 212 and a concave image-side surface 214, and is aspheric, and the object-side surface 212 has an inflection point.

The second lens element 220 with positive refractive power has a convex object-side surface 222 and a concave image-side surface 224, and is aspheric, and the object-side surface 222 has an inflection point.

The third lens element 230 with positive refractive power has a convex object-side surface 232 and a convex image-side surface 234, and is aspheric, and the object-side surface 232 has an inflection point.

The fourth lens element 240 with negative refractive power has a convex object-side surface 242 and a concave image-side surface 244, and is aspheric, and the object-side surface 242 has an inflection point.

The infrared filter 270 is made of glass, and is disposed between the fourth lens element 240 and the image plane 280 without affecting the focal length of the optical imaging system.

Please refer to the following table three and table four.

TABLE IV aspheric coefficients of the second embodiment

In the second embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.

According to the third table and the fourth table, the following conditional expressions can be obtained:

the values associated with the profile curve length can be obtained according to table three and table four:

third embodiment

Referring to fig. 7 to 9, wherein fig. 7 is a schematic view illustrating an optical imaging system according to a third embodiment of the present invention, and fig. 8 is a graph illustrating spherical aberration, astigmatism and optical distortion of the optical imaging system according to the third embodiment in order from left to right. Fig. 9 is a diagram showing a visible spectrum modulation conversion characteristic of the optical imaging system of the third embodiment. In fig. 7, the optical imaging system 30 includes, in order from an object side to an image side, a first lens element 310, an aperture stop 300, a second lens element 320, a third lens element 330, a fourth lens element 340, an ir-filter 370, an image plane 380, and an image sensor 390.

The first lens element 310 with negative refractive power has a concave object-side surface 312 and a convex image-side surface 314, and is aspheric, and the object-side surface 312 and the image-side surface 314 have two inflection points.

The second lens element 320 with positive refractive power has a concave object-side surface 322 and a convex image-side surface 324.

The third lens element 330 with positive refractive power has a concave object-side surface 332 and a convex image-side surface 334, and is aspheric, and the object-side surface 332 and the image-side surface 334 both have inflection points.

The fourth lens element 340 with negative refractive power has a concave object-side surface 342 and a concave image-side surface 344, which are both aspheric, and has an inflection point on the object-side surface 332 and two inflection points on the image-side surface 334.

The infrared filter 370 is made of glass, and is disposed between the fourth lens element 340 and the image plane 380 without affecting the focal length of the optical imaging system.

Please refer to table five and table six below.

TABLE sixth, aspherical coefficients of the third example

In the third embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.

According to table five and table six, the following conditional values can be obtained:

fourth embodiment

Referring to fig. 10 to 12, wherein fig. 10 is a schematic view illustrating an optical imaging system according to a fourth embodiment of the present invention, and fig. 11 is a graph illustrating spherical aberration, astigmatism and optical distortion of the optical imaging system according to the fourth embodiment in order from left to right. Fig. 12 is a diagram showing a visible spectrum modulation conversion characteristic of the optical imaging system of the fourth embodiment. In fig. 10, the optical imaging system 40 includes, in order from an object side to an image side, a first lens element 410, an aperture stop 400, a second lens element 420, a third lens element 430, a fourth lens element 440, an ir-filter 470, an image plane 480 and an image sensor 490.

The first lens element 410 with negative refractive power has a concave object-side surface 412 and a concave image-side surface 414, which are both aspheric, and the object-side surface 412 has an inflection point.

The second lens element 420 with positive refractive power has a convex object-side surface 422 and a convex image-side surface 424, and is aspheric, and the object-side surface 422 has a inflection point.

The third lens element 430 with positive refractive power has a convex object-side surface 432 and a concave image-side surface 434, and is aspheric, and the object-side surface 432 has an inflection point.

The fourth lens element 440 with negative refractive power has a concave object-side surface 442 and a convex image-side surface 444, and is aspheric, and the image-side surface 444 has an inflection point.

The ir filter 470 is made of glass, and is disposed between the fourth lens element 440 and the image plane 480 without affecting the focal length of the optical imaging system.

Please refer to table seven and table eight below.

TABLE eighth, fourth example aspherical surface coefficients

In the fourth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.

According to the seventh and eighth tables, the following conditional values can be obtained:

fifth embodiment

Referring to fig. 13 to 15, wherein fig. 13 is a schematic view of an optical imaging system according to a fifth embodiment of the present invention, and fig. 14 is a graph of spherical aberration, astigmatism and optical distortion of the optical imaging system according to the fifth embodiment in order from left to right. Fig. 15 is a diagram showing a visible spectrum modulation conversion characteristic of the optical imaging system of the fifth embodiment. In fig. 13, the optical imaging system 50 includes, in order from an object side to an image side, a first lens element 510, an aperture stop 500, a second lens element 520, a third lens element 530, a fourth lens element 540, an ir-filter 570, an image plane 580 and an image sensor 590.

The first lens element 510 with negative refractive power has a convex object-side surface 512 and a concave image-side surface 514, and is aspheric, and the object-side surface 512 and the image-side surface 314 have inflection points.

The second lens element 520 with positive refractive power has a convex object-side surface 522 and a concave image-side surface 524, which are both aspheric, and the object-side surface 522 has an inflection point.

The third lens element 530 with positive refractive power has a convex object-side surface 532 and a convex image-side surface 534, and is aspheric, and the object-side surface 532 has two inflection points.

The fourth lens element 540 with negative refractive power has a convex object-side surface 542 and a convex image-side surface 544, and is aspheric, and the image-side surface 544 has an inflection point.

The infrared filter 570 is made of glass, and is disposed between the fourth lens element 540 and the image plane 580 without affecting the focal length of the optical imaging system.

Please refer to table nine and table ten below.

Aspherical surface coefficients of Table ten and fifth example

In the fifth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.

The following conditional values are obtained according to table nine and table ten:

sixth embodiment

Referring to fig. 16 to 18, wherein fig. 16 is a schematic view illustrating an optical imaging system according to a sixth embodiment of the present invention, and fig. 17 is a graph illustrating spherical aberration, astigmatism and optical distortion of the optical imaging system according to the sixth embodiment in order from left to right. Fig. 18 is a diagram showing a visible spectrum modulation conversion characteristic of the optical imaging system of the sixth embodiment. In fig. 16, the optical imaging system 60 includes, in order from an object side to an image side, a first lens element 610, an aperture stop 600, a second lens element 620, a third lens element 630, a fourth lens element 640, an ir-filter 670, an image plane 680 and an image sensor 690.

The first lens element 610 with negative refractive power has a convex object-side surface 612 and a concave image-side surface 614, and is aspheric, and the object-side surface 612 has an inflection point.

The second lens element 620 with positive refractive power has a convex object-side surface 622 and a convex image-side surface 624, and is aspheric, and the object-side surface 622 has an inflection point.

The third lens element 630 with positive refractive power has a concave object-side surface 632, a convex image-side surface 634, and an inflection point on both the object-side surface 632 and the image-side surface 634.

The fourth lens element 640 with negative refractive power has a convex object-side surface 642 and a concave image-side surface 644, which are both aspheric, and has an inflection point on an object-side surface 632 and two inflection points on an image-side surface 634.

The infrared filter 670 is made of glass, and is disposed between the fourth lens element 640 and the image plane 680 without affecting the focal length of the optical imaging system.

Please refer to the following table eleven and table twelve.

TABLE twelfth and sixth examples of aspherical surface coefficients

In the sixth embodiment, the curve equation of the aspherical surface represents the form as in the first embodiment. In addition, the following parameters are defined in the same way as in the first embodiment and will not be described herein.

The following conditional values were obtained according to table eleven and table twelve:

although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.

Claims

1. An optical imaging system, in order from an object side to an image side comprising:

a first lens element with negative refractive power having a concave object-side surface on an optical axis and at least one inflection point;

a second lens element with refractive power;

a third lens element with positive refractive power having a concave object-side surface on an optical axis;

a fourth lens element with refractive power; and

an imaging surface;

wherein four lenses having refractive power in the optical imaging system, at least one of the second lens element and the fourth lens element has positive refractive power, focal lengths of the first lens element to the fourth lens element are respectively f1, f2, f3 and f4, the focal length of the optical imaging system is f, an entrance pupil diameter of the optical imaging system is HEP, a distance HOS is provided on an optical axis from an object-side surface of the first lens element to the image plane, a distance idtl is provided on the optical axis from the object-side surface of the first lens element to the image-side surface of the fourth lens element, a half of a maximum visual angle of the optical imaging system is HAF, thicknesses of the first lens element, the second lens element, the third lens element and the fourth lens element, which are at a height of 1/2HEP and parallel to the optical axis, are respectively ETP1, ETP2, ETP3 and ETP4, a sum of the ETP1 to ETP4 is SETP, and a sum of the first lens element is SETP 4, The thicknesses of the second lens, the third lens and the fourth lens on the optical axis are TP1, TP2, TP3 and TP4 respectively, the sum of the TP1 to the TP4 is STP, and the following conditions are satisfied: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.5 ≤ SETP/STP < 1.

2. The optical imaging system of claim 1, wherein a horizontal distance parallel to the optical axis between a coordinate point on the object-side surface of the first lens at a height of 1/2HEP and the image plane is ETL, and a horizontal distance parallel to the optical axis between a coordinate point on the object-side surface of the first lens at a height of 1/2HEP and a coordinate point on the image-side surface of the fourth lens at a height of 1/2HEP is EIN, wherein the following conditions are satisfied: EIN/ETL is more than or equal to 0.2 and less than 1.

3. The optical imaging system of claim 2, wherein it satisfies the following formula: SETP/EIN is more than or equal to 0.3 and less than 1.

4. The optical imaging system of claim 1, wherein the second lens element has positive refractive power and an object-side surface that is concave on an optical axis.

5. The optical imaging system of claim 4, wherein the image-side surface of the first lens element is convex along the optical axis and the image-side surface of the second lens element is convex along the optical axis.

6. The optical imaging system of claim 1, wherein the image-side surface of the third lens element is convex along the optical axis.

7. The optical imaging system of claim 1, wherein the object-side surface and the image-side surface of the fourth lens are convex on the optical axis.

8. The optical imaging system according to claim 1, wherein an imaging height of the optical imaging system is HOI, and modulation conversion contrast transfer ratios of visible light at three spatial frequencies of 55cycles/mm on the imaging plane, namely, an optical axis of visible light, 0.3HOI and 0.7HOI, are expressed as MTFE0, MTFE3 and MTFE7, respectively, satisfy the following conditions: MTFE0 is more than or equal to 0.2; MTFE3 is more than or equal to 0.01; and MTFE7 is not less than 0.01.

9. The optical imaging system of claim 1, further comprising an aperture and having a distance InS on an optical axis from the aperture to the image plane that satisfies the following equation: 0.2-1.1 of InS/HOS.

10. An optical imaging system, in order from an object side to an image side comprising:

a second lens element with refractive power;

a third lens element with positive refractive power having a concave object-side surface on an optical axis and at least one inflection point;

a fourth lens element with refractive power; and

an imaging surface;

wherein four lenses having refractive power in the optical imaging system, at least one of the second lens element and the fourth lens element has positive refractive power, the focal lengths from the first lens element to the fourth lens element are f1, f2, f3 and f4, respectively, the focal length of the optical imaging system is f, the diameter of the entrance pupil of the optical imaging system is HEP, a distance HOS is provided from the object-side surface of the first lens element to the image plane on the optical axis, a distance idtl is provided from the object-side surface of the first lens element to the image-side surface of the fourth lens element on the optical axis, a half of the maximum visible angle of the optical imaging system is HAF, a horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the image plane parallel to the optical axis is ETL, a horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the image-side surface of the fourth lens element parallel to the HEP height of 1/2 on the image-side surface is EIN Which satisfies the following conditions: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.2 ≤ EIN/ETL < 1.

11. The optical imaging system according to claim 10, wherein an imaging height of the optical imaging system is HOI, and modulation conversion contrast transfer rates of visible light at the optical axis, 0.3HOI and 0.7HOI on the imaging plane are expressed by MTFQ0, MTFQ3 and MTFQ7, respectively, which satisfy the following conditions: MTFQ0 is more than or equal to 0.2; MTFQ3 is more than or equal to 0.01; and MTFQ7 is more than or equal to 0.01.

12. The optical imaging system of claim 10, wherein the optical imaging system satisfies the following equation: HOS is more than 0mm and less than or equal to 4 mm.

13. The optical imaging system of claim 10, wherein the second lens has a thickness ETP2 at 1/2HEP height and parallel to the optical axis, and the second lens has a thickness TP2 on the optical axis, satisfying the following conditions: ETP2/TP2 of 0.1-5.

14. The optical imaging system of claim 10, wherein the second lens element has positive refractive power and an object-side surface that is concave along an optical axis.

15. The optical imaging system of claim 10, wherein the optical imaging system satisfies the following condition: -3. ltoreq. f2/f 3. ltoreq.5.

16. The optical imaging system of claim 10, wherein the optical imaging system satisfies the following condition: f2< f 3.

17. The optical imaging system of claim 10, wherein the optical imaging system satisfies the following condition: -2. ltoreq. f1/f 4. ltoreq.3.

18. The optical imaging system of claim 10, wherein the thicknesses of the second lens and the third lens on the optical axis are TP2 and TP3, respectively, which satisfy the following condition: TP2/TP3 is more than or equal to 0.1 and less than or equal to 10.

19. The optical imaging system of claim 10, wherein the thicknesses of the second lens and the third lens on the optical axis are TP2 and TP3, respectively, which satisfy the following condition: TP2> TP 3.

20. An optical imaging system, in order from an object side to an image side comprising:

a first lens element with negative refractive power having a concave object-side surface and a convex image-side surface, both of which have at least one inflection point;

a second lens element with positive refractive power having a concave object-side surface on an optical axis;

a fourth lens element with refractive power; and

an imaging surface;

wherein the optical imaging system comprises four lenses with refractive power, the focal lengths of the first lens element to the fourth lens element are f1, f2, f3 and f4, respectively, the focal length of the optical imaging system is f, the diameter of the entrance pupil of the optical imaging system is HEP, the distance HOS is between the object-side surface of the first lens element and the imaging surface along the optical axis, the distance idtl is between the object-side surface of the first lens element and the image-side surface of the fourth lens element along the optical axis, half of the maximum viewing angle of the optical imaging system is HAF, the horizontal distance between the coordinate point at the HEP height of 1/2 on the object-side surface of the first lens element and the imaging surface along the optical axis is ETL, the horizontal distance between the point at the HEP height of 1/2 on the object-side surface of the first lens element and the coordinate point at the HEP height of 1/2 on the image-side surface of the fourth lens element along the optical axis is EIN, it satisfies the following conditions: f/HEP is more than or equal to 1.8 and less than or equal to 2.8; 45deg < HAF ≤ 80deg and 0.2 ≤ EIN/ETL < 1.

21. The optical imaging system of claim 20, wherein the distance between the third lens and the fourth lens on the optical axis is IN34, and the following formula is satisfied: 0< IN34/f is less than or equal to 5.

22. The optical imaging system of claim 20, wherein the optical imaging system satisfies the following condition: f2/f3 is more than or equal to 0.1 and less than or equal to 5.

23. The optical imaging system of claim 20, wherein the fourth lens element has a concave object-side surface and a concave image-side surface on the optical axis.

24. The optical imaging system of claim 20, wherein the image side surface of the fourth lens has at least two points of inflection.

25. The optical imaging system of claim 20, further comprising an aperture stop, an image sensor disposed on the image plane and having a distance InS from the aperture stop to the image plane, and a driving module coupled to the first lens element to the fourth lens element and configured to displace the first lens element to the fourth lens element, wherein the following equation is satisfied: 0.2-1.1 of InS/HOS.