Imaging optical system and camera module applying same

Abstract

The invention provides an imaging optical system and a camera module applying the same. A first lens has negative focal power, the object side surface of the first lens is a plane, and the image side surface of the first lens is a concave surface; the second lens has positive focal power, and the object side surface of the second lens is a convex surface; the third lens has focal power; the fourth lens has positive focal power, the object side surface of the fourth lens is a convex surface, and the image side surface of the fourth lens is a convex surface; the fifth lens has positive focal power, and the image side surface of the fifth lens is a convex surface; the sixth lens has negative focal power, and the object side surface of the sixth lens is a concave surface; by reasonably configuring the refractive power and the surface type of each lens, the optical lens can have the characteristics of small caliber, large field angle, high relative illumination and high resolution, and meanwhile, the total length of the lens is short, and the lens is lighter than a glass lens, so that the requirements of compactness and light weight are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical imaging, in particular to an imaging optical system and a camera module using the same. BACKGROUND

[0002] As an examination and treatment instrument, endoscopes have been widely used due to their advantage of being able to directly enter the human body for observation. With the rapid development of clinical medical detection technology and minimally invasive surgery, in order to alleviate the discomfort caused by, for example, a gastrointestinal mirror and facilitate the flexibility of the lens after entering the human body, it is often required that the endoscope has a front end outer diameter size as small as possible. In order to facilitate the acquisition of information for diagnosis and observation, it is required that the endoscope has a large field of view to obtain sufficient observation field of view and avoid poor illumination around the field of view caused by the edge dark angle. However, under the condition of small caliber, it is often faced with significant contradictions to realize large field of view imaging: the limited caliber of the front end lens makes it difficult for the edge light beam to fully enter, resulting in limited field of view angle; and the increase of the light beam incidence angle will cause the edge dark angle to deepen and the resolution to be insufficient.

[0003] Therefore, how to realize a large field of view angle in a limited small caliber, ensure the edge illumination and imaging quality, and take into account the compactness and lightness of the system has become the research and development direction of the current endoscope optical system. SUMMARY

[0004] The present application provides an imaging optical system, which has the characteristics of small caliber, large field of view angle, high relative illumination and high resolution by reasonably configuring the refractive power and surface type of each lens, and at the same time, the total length of the lens is short, and the lens is lighter than the glass lens, so as to meet the needs of compactness and lightness.

[0005] The present application adopts the following technical solutions: 1. An imaging optical system, which is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens and a sixth lens in sequence from an object plane to an image plane along an optical axis; The first lens has a negative focal power, and its object side surface is a plane and its image side surface is a concave surface; The second lens has a positive focal power, and its object side surface is a convex surface; The third lens has a focal power; The fourth lens has a positive focal power, and its object side surface is a convex surface and its image side surface is a convex surface; The fifth lens has a positive focal power, and its image side surface is a convex surface; The sixth lens has a negative focal power, and its object side surface is a concave surface.

[0006] Further, the imaging optical system satisfies the following relationship: 0.7<|f2 / R3|<2.1; 1.2 < (R7-R8) / (R7+R8) < 3.6; wherein f2 is the focal length of the second lens, R3 is the radius of curvature of the image side surface of the second lens, R7 is the radius of curvature of the object side surface of the fourth lens, and R8 is the radius of curvature of the image side surface of the fourth lens.

[0007] Further, the imaging optical system satisfies the following relationship: 1.2 < |f2 / f1| < 2.3; 0.7 < |f3-f4| / |f3+f4| < 3.0; wherein f2 is the focal length of the second lens, f1 is the focal length of the first lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

[0008] Further, the imaging optical system satisfies the following relationship: 1.8 < |f123 / f456| < 3.6; 1.5 < |f56 / f| < 3.5; wherein f123 is the combined focal length of the first lens, the second lens and the third lens, f456 is the combined focal length of the fourth lens, the fifth lens and the sixth lens, f56 is the combined focal length of the fifth lens and the sixth lens, and f is the effective focal length of the entire optical system.

[0009] Further, the imaging optical system satisfies the following relationship: 10.0 mm < (FNO*f*IMGH) / DT11 < 12.5 mm; wherein FNO is the F number of the optical imaging lens, f is the effective focal length of the imaging optical system, IMGH is half of the diagonal length of the effective pixel area on the imaging surface of the optical system, and DT11 is half of the maximum effective clear aperture diameter of the object side surface of the first lens.

[0010] Further, the imaging optical system satisfies the following relationship: 8.0 < (tan(HFOV)*TTL) / IMGH < 11.2; wherein HFOV is half of the maximum field of view angle of the imaging optical system, TTL is the axial distance from the object side surface of the first lens to the imaging surface, and IMGH is half of the diagonal length of the effective pixel area on the imaging surface of the optical system.

[0011] Further, the imaging optical system satisfies the following relationship: 2.4 < (CT1+CT2) / T12 < 4.7; wherein CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the axial distance from the image side surface of the first lens to the object side surface of the second lens.

[0012] Further, the imaging optical system satisfies the following relationship: the imaging optical system satisfies the following relationship: 2.4 < ΣCT / ΣAT < 3.5; Wherein, ΣCT is the sum of the center thickness of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens on the optical axis, and ΣAT is the sum of the axial distance from the image side surface of the first lens to the object side surface of the second lens, the axial distance from the image side surface of the second lens to the object side surface of the third lens, the axial distance from the image side surface of the third lens to the object side surface of the fourth lens, the axial distance from the image side surface of the fourth lens to the object side surface of the fifth lens, and the axial distance from the image side surface of the fifth lens to the object side surface of the sixth lens.

[0013] Further, the F number of the imaging optical system is ≤6, the total length is ≤4.7 mm, the lens diameter is ≤2 mm, and the field of view angle is ≥140°.

[0014] Further, the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens are all aspherical lenses.

[0015] Another object of the present application is to provide a camera module comprising at least an optical lens, wherein the optical lens is internally mounted with the above-mentioned imaging optical system.

[0016] Compared with the prior art, the present application has the following advantages: The present application provides an imaging optical system and a camera module using the same, which is composed of six lenses. By reasonably configuring the refractive power and surface shape of each lens, the optical lens can have the characteristics of small aperture, large field of view angle, high relative luminance and high resolution, and the total length of the lens is short and the lens is lighter than the glass lens, so as to meet the requirements of compactness and lightness. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows.

[0018] Figure 1 is a structural schematic diagram of the optical system or camera module of the embodiment 1 of the present application; Figure 2 is the axial chromatic aberration, astigmatism and distortion curve of the optical system or camera module of the embodiment 1 of the present application; Figure 3 is the relative luminance curve of the optical system or camera module of the embodiment 1 of the present application; Figure 4 is a structural schematic diagram of the optical system or camera module of the embodiment 2 of the present application; Figure 5 is the axial chromatic aberration, astigmatism and distortion curve of the optical system or camera module of the embodiment 2 of the present application; Figure 6 is a relative illumination curve of the optical system or camera module of Embodiment 2 of the present application; Figure 7 is a structural schematic diagram of the optical system or camera module of Embodiment 3 of the present application; Figure 8 is an on-axis chromatic aberration, astigmatism and distortion curve of the optical system or camera module of Embodiment 3 of the present application; Figure 9 is a relative illumination curve of the optical system or camera module of Embodiment 3 of the present application; Figure 10 is a structural schematic diagram of the optical system or camera module of Embodiment 4 of the present application; Figure 11 is an on-axis chromatic aberration, astigmatism and distortion curve of the optical system or camera module of Embodiment 4 of the present application; Figure 12 is a relative illumination curve of the optical system or camera module of Embodiment 4 of the present application. DETAILED DESCRIPTION

[0019] The present application provides an imaging optical system, comprising, from the object side, a first lens E1, a second lens E2, a third lens E3, a stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6 and an infrared filter E7; the first lens E1 has a negative focal power, the object side surface thereof is a plane, and the image side surface thereof is a concave surface; the second lens E2 has a positive focal power, the object side surface thereof is a convex surface; the third lens E3 has a focal power; the fourth lens E4 has a positive focal power, the object side surface thereof is a convex surface, and the image side surface thereof is a convex surface; the fifth lens E5 has a positive focal power, the image side surface thereof is a convex surface; and the sixth lens E6 has a negative focal power, the object side surface thereof is a concave surface. The optical system of the embodiment of the present application is composed of six lenses. By reasonably configuring the refractive power and surface shape of each lens, the optical lens can have the characteristics of small aperture, large field of view, high relative illumination and high resolution, and the overall length of the lens is short, and the lens is lighter than the glass lens, so as to meet the needs of compactness and lightness.

[0020] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 10.0 mm < FNO*f*IMGH / DT11 < 12.5 mm, wherein FNO is the F number of the optical imaging lens, f is the effective focal length of the optical imaging system, IMGH is half of the diagonal length of the effective pixel area on the imaging surface of the optical system, and DT11 is half of the maximum effective entrance pupil radius of the object side of the first lens. The relationship reflects the constraints of the optical lens in terms of large field of view, small aperture, and aperture characteristics. Satisfying the relationship enables the optical system to have sufficient light intake while having the advantages of small aperture and large field of view, and enables the front lens aperture to be sufficient to support the combination of the field of view and the aperture. When lower than the lower limit of the relationship, the optical imaging system cannot meet the requirement of a large field of view; and when higher than the upper limit of the relationship, the optical imaging system cannot obtain sufficient light intake, and is prone to edge dark corners and reduced resolution.

[0021] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 8.0 < tan(HFOV)*TTL / IMGH < 11.2, wherein HFOV is half of the maximum field of view angle of the optical imaging system, TTL is the axial distance from the object side of the first lens to the imaging surface, and IMGH is half of the diagonal length of the effective pixel area on the imaging surface of the optical system. The formula can ensure that a small-size large-field-of-view optical system has sufficient image height, so that the system still has a certain margin in imaging image height under the characteristics of compact size and large field of view. When lower than the lower limit of the relationship, the field of view and the corresponding image height are too large relative to the current TTL, and the front lens will be shaded or have edge dark corners; and when higher than the upper limit of the relationship, it is difficult to realize the required large field of view or large effective image surface in a compact and small optical system.

[0022] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 0.7 < |f2 / R3| < 2.1, wherein f2 is the focal length of the second lens, and R3 is the curvature radius of the image side of the second lens. The formula reflects the shape of the image side of the second lens, and through the formula, it can be ensured that the image side of the second lens will not be excessively curved, the tolerance sensitivity of high-order aberrations of the surface in processing, coating, and assembly is reduced, and the feasibility of lens molding and lens thickness manufacturing is maintained. When lower than the lower limit of the relationship, it is difficult to correct the chromatic aberration of the optical system; and when higher than the upper limit of the relationship, the eccentricity and tilt sensitivity of the second lens increases, the mold precision requirement is higher, which causes problems of yield reduction and cost increase.

[0023] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 1.2 < (R7-R8) / (R7+R8) < 3.6, wherein R7 is the curvature radius of the object side surface of the fourth lens, and R8 is the curvature radius of the image side surface of the fourth lens. The formula reflects the asymmetry of the two sides of the fourth lens, controls the influence of the spherical aberration and the astigmatism generated by the lens on the whole system, and reduces the manufacturing difficulty of the lens. When lower than the lower limit of the relationship, the compensation ability for the asymmetric aberration is insufficient; when higher than the upper limit of the relationship, the sensitivity of the fourth lens to the processing and assembly errors is increased.

[0024] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 1.2 < |f2 / f1| < 2.3, wherein f2 is the focal length of the second lens, and f1 is the focal length of the first lens. The formula reflects the ratio of the effective focal lengths of the second lens and the first lens, ensures the balance among the entrance pupil position, the entrance pupil diameter, and the aberration correction distribution, ensures that the aberration distribution is controllable and the front lens size meets the requirements. When lower than the lower limit of the relationship, the first lens bears more aberration correction functions, and the manufacturing and coating difficulty of the first lens is increased; when higher than the upper limit of the relationship, the change of the entrance pupil position affects the sensitivity of the system, and the processing difficulty of the second lens is increased.

[0025] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 0.7 < |f3-f4| / |f3+f4| < 3.0, wherein f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens. The formula reflects the symmetry of the third lens and the fourth lens, and by limiting the ratio, the distribution of the third lens and the fourth lens can be ensured, the uniformity of the image quality of the system is maintained, the system has a certain degree of freedom but does not produce uncontrollable aberration. When lower than the value, the freedom of the two lenses is small, which limits the correction ability of the optical system to the coma and the astigmatism; when higher than the upper limit of the relationship, one of the lenses bears too much aberration correction function, the system is more asymmetric, which is easy to bring the assembly error in the manufacturing, and additionally increases the process difficulty and cost.

[0026] As a preferred embodiment of the present application but not as a limitation, the imaging optical system satisfies the following relationship: 1.8 < |f123 / f456| < 3.6, wherein f123 is the combined focal length of the first lens, the second lens and the third lens, and f456 is the combined focal length of the fourth lens, the fifth lens and the sixth lens. The formula reflects the balance of the imaging performance and the aberration correction ability of the lens group and the rear lens, so that the system can meet the focal length requirement while reasonably controlling the entrance pupil position and the edge image quality. When lower than the lower limit of the relationship, the focal length of the front lens group is too small, which leads to the increase of the chief ray angle, the increase of the distortion, the insufficient illumination of the edge field of view, and the decrease of the resolution; when higher than the upper limit of the relationship, the focal length of the rear lens group is too small, which leads to the backward movement of the entrance pupil position, the lengthening of the overall structure, and the disadvantage of the compactness.

[0027] As a preferred embodiment of the present application but not limited, the imaging optical system satisfies the following relationship: 1.5 < |f56 / f| < 3.5, wherein f56 is the combined focal length of the fifth lens and the sixth lens, and f is the effective focal length of the entire optical system. The formula reflects that the rear-end lens ensures the effective focal length ratio of the entire optical system. The adjustment capability of the effective focal length and the correction capability of coma and chromatic aberration. When lower than the lower limit of the relationship, it is not conducive to the small aperture design of the front-end lens, and the manufacturing difficulty of the front-end lens increases; when higher than the upper limit of the relationship, there is a problem of light blocking in the rear-end lens, and it is difficult to ensure the image quality of the edge field of view of imaging.

[0028] As a preferred embodiment of the present application but not limited, the imaging optical system satisfies the following relationship: 2.4 < (CT1+CT2) / T12 < 4.7, wherein CT1 is the central thickness of the first lens on the optical axis, CT2 is the central thickness of the second lens on the optical axis, and T12 is the axial distance from the image side surface of the first lens to the object side surface of the second lens. The formula reflects the concentration degree of the length distribution of the first lens and the second lens on the axis relative to the front lens spacing, and ensures that the lens position and thickness arrangement of the optical system are reasonable by satisfying the formula, the light has a suitable space between the lenses for aberration correction, and the imaging stability is maintained. When lower than the lower limit of the relationship, there is not enough space to place optical elements, which limits the freedom of aberration correction; when higher than the upper limit of the relationship, the lens spacing is too small, which affects the layout balance and the entrance pupil position, and is easy to cause light blocking at the front lens.

[0029] As a preferred embodiment of the present application but not limited, the imaging optical system satisfies the following relationship: 2.4 < ΣCT / ΣAT < 3.5, wherein ΣCT is the sum of the central thicknesses of the first lens, the second lens, the third lens, the fourth lens, the fifth lens and the sixth lens on the optical axis, and ΣAT is the sum of the axial distances from the image side surface of the first lens to the object side surface of the second lens, from the image side surface of the second lens to the object side surface of the third lens, from the image side surface of the third lens to the object side surface of the fourth lens, from the image side surface of the fourth lens to the object side surface of the fifth lens, and from the image side surface of the fifth lens to the object side surface of the sixth lens. The formula reflects the ratio of the total length of the lens material to the sum of the air gaps, which ensures the manufacturing feasibility and the margin during lens assembly, ensures the weight balance of the lens, and reduces internal reflection and absorption. When lower than the lower limit of the relationship, the sensitivity to air gap tolerance increases significantly, which brings assembly and thermal expansion problems; when higher than the upper limit of the relationship, the thicker lens brings injection molding problems, the tilt and eccentricity errors of the lens affect the yield of the lens, the weight of the lens increases, and the structure of the lens barrel is more complex, which is not conducive to the lightweight of the lens.

[0030] As a preferred embodiment of the present application but not a limitation, the imaging optical system satisfies the following relationships: F number of the imaging optical system ≤ 6, total length ≤ 4.7 mm, lens diameter ≤ 2 mm, and field of view angle ≥ 140°. The first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 are aspherical lenses and are separated by air. The endoscope objective optical system of the present application has the characteristics of small caliber, large field of view angle, high relative luminance, and high resolution, and has a short total length and a compact structure. The use of plastic lenses reduces the weight of the lens.

[0031] Embodiment one, The following refers to Figures 1 to 3 An optical imaging lens according to Embodiment 1 of the present application is described. Figure 1 An optical imaging lens according to Embodiment 1 of the present application is described.

[0032] As Figure 1 shown, the optical imaging lens according to an exemplary embodiment of the present application includes, in order from the object side to the image side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, an infrared filter E7, an image sensor protection lens E8, and an imaging surface S17.

[0033] The first lens E1 has a negative focal power, the object side surface S1 is a plane, and the image side surface S2 is a concave surface. The second lens E2 has a positive focal power, the object side surface S3 is a convex surface, and the image side surface S4 is a convex surface. The third lens E3 has a negative focal power, the object side surface S5 is a concave surface, and the image side surface S6 is a concave surface. The fourth lens E4 has a positive focal power, the object side surface S7 is a convex surface, and the image side surface S8 is a convex surface. The fifth lens E5 has a positive focal power, the object side surface S9 is a convex surface, and the image side surface S10 is a convex surface. The sixth lens E6 has a negative focal power, the object side surface S11 is a concave surface, and the image side surface S12 is a concave surface. The filter E7 has an object side surface S13 and an image side surface S14. The image sensor CCD protection lens E8 has an object side surface S15 and an image side surface S16. Light from an object sequentially passes through the surfaces S1 to S16 and is finally imaged on the imaging surface S17.

[0034] Table 1 shows the surface type, the radius of curvature, the thickness, and the material of each lens of the optical imaging lens of Embodiment 1, wherein the units of the radius of curvature and the thickness are millimeters (mm).

[0035] Table 1

[0036] In Table 1, the image-side surface of the first lens E1, and the object-side and image-side surfaces of any one of the lenses E2, E3, E4, E5, and E6 are all Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0037] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, and a m r is the aspherical coefficient. max The maximum value of the radial radius coordinate is u = r / r max Table 2 provides the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28 and A30 for each aspherical surface that can be used in the first embodiment.

[0038] Table 2

[0039] Example 2 The following is for reference Figures 4 to 6 Describes an optical imaging lens according to Embodiment 2 of this application. Figure 4 A schematic diagram of the structure of an optical imaging lens according to Embodiment 2 of this application is shown.

[0040] like Figure 1 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, an aperture stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, an infrared filter E7, an image sensor protective lens E8, and an imaging surface S15.

[0041] The first lens E1 has negative optical power, with its object-side surface S1 being flat and its image-side surface S2 being concave. The second lens E2 has positive optical power, with its object-side surface S3 being convex and its image-side surface S4 being concave. The third lens E3 has negative optical power, with its object-side surface S5 being convex and its image-side surface S6 being concave. The fourth lens E4 has positive optical power, with its object-side surface S7 being convex and its image-side surface S8 being convex. The fifth lens E5 has positive optical power, with its object-side surface S9 being concave and its image-side surface S10 being convex. The sixth lens E6 has negative optical power, with its object-side surface S11 being concave and its image-side surface S12 being concave. The filter E7 has an object-side surface S13 and an image-side surface S14, and the CCD protective lens E8 of the image sensor has an object-side surface S15 and an image-side surface S16. Light from the object passes sequentially through each surface S1 to S16 and is finally imaged onto the imaging surface S17.

[0042] Table 3 shows the surface type, radius of curvature, thickness, and material of each lens in the optical imaging lens of Example 2, wherein the units for radius of curvature and thickness are millimeters (mm).

[0043] Table 3

[0044] In Table 3, the object-side surface and image-side surface of any one of the lenses E1, E2, E3, E4, E5, and E6 are Q-type aspherical surfaces. The surface shape of each aspherical lens can be defined using, but is not limited to, the following aspherical formulas:

[0045] Where Z is the distance from the corresponding point on the aspherical surface to the plane tangent to the vertex of the surface, r is the radial coordinate of the aspherical surface, c is the curvature of the vertex of the aspherical surface, K is the conic coefficient, and a m r is the aspherical coefficient. max The maximum value of the radial radius coordinate is u = r / r max Table 4 provides the conic coefficients and higher-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28 and A30 for each aspherical surface that can be used in the second embodiment.

[0046] Table 4

[0047] Example 3 The following is for reference Figures 7 to 9 Describes an optical imaging lens according to Embodiment 3 of this application. Figure 7 A schematic diagram of the structure of an optical imaging lens according to Embodiment 3 of this application is shown.

[0048] like Figure 5 As shown, the optical imaging lens according to an exemplary embodiment of this application includes, in sequence along the optical axis from the object side to the image side: a first lens E1, a second lens E2, a third lens E3, an aperture stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, an infrared filter E7, an image sensor protective lens E8, and an imaging surface S15.

[0049] The first lens E1 has negative focal power, the object side surface S1 is a plane, and the image side surface S2 is a concave surface. The second lens E2 has positive focal power, the object side surface S3 is a convex surface, and the image side surface S4 is a convex surface. The third lens E3 has negative focal power, the object side surface S5 is a concave surface, and the image side surface S6 is a concave surface. The fourth lens E4 has positive focal power, the object side surface S7 is a convex surface, and the image side surface S8 is a convex surface. The fifth lens E5 has positive focal power, the object side surface S9 is a concave surface, and the image side surface S10 is a convex surface. The sixth lens E6 has negative focal power, the object side surface S11 is a concave surface, and the image side surface S12 is a convex surface. The filter E7 has an object side surface S13 and an image side surface S14. The image sensor CCD protective lens E8 has an object side surface S15 and an image side surface S16. Light from an object sequentially passes through the surfaces S1 to S16 and is finally imaged on the imaging surface S17.

[0050] Table 5 shows the surface type, the radius of curvature, the thickness and the material of each lens of the optical imaging lens of Example 3, wherein the units of the radius of curvature and the thickness are millimeters (mm).

[0051] Table 5

[0052] In Table 5, the object side surface and the image side surface of each of the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5 and the sixth lens E6 are Q type aspheric surfaces. The surface type of each aspheric surface can be defined by, but not limited to, the following aspheric surface formula:

[0053] wherein Z is the distance from a corresponding point on the aspheric surface to a plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the vertex of the aspheric surface, K is the conic coefficient, a m is the aspheric coefficient, r max is the maximum radial radius coordinate, and u = r / r max Table 6 shows the conic coefficient and the high order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28 and A30 of each aspheric surface that can be used in the third embodiment.

[0054] Table 6

[0055] Example Four, The optical imaging lens according to the fourth embodiment of the present application is described below with reference to Figures 10 to 12 The structure of the optical imaging lens according to the fourth embodiment of the present application is shown in FIG. 4. Figure 10 The structure of the optical imaging lens according to the fourth embodiment of the present application is shown in FIG. 4.

[0056] AsFigure 7 As shown, the optical imaging lens according to the exemplary embodiment of the present application comprises, in sequence from the object side to the image side along the optical axis, a first lens E1, a second lens E2, a third lens E3, a stop STO, a fourth lens E4, a fifth lens E5, a sixth lens E6, an infrared filter E7, an image sensor protection lens E8, and an imaging surface S15.

[0057] The first lens E1 has a negative focal power, the object side surface S1 is a plane, and the image side surface S2 is a concave surface; the second lens E2 has a positive focal power, the object side surface S3 is a convex surface, and the image side surface S4 is a concave surface; the third lens E3 has a positive focal power, the object side surface S5 is a concave surface, and the image side surface S6 is a convex surface; the fourth lens E4 has a positive focal power, the object side surface S7 is a convex surface, and the image side surface S8 is a convex surface; the fifth lens E5 has a positive focal power, the object side surface S9 is a convex surface, and the image side surface S10 is a convex surface; the sixth lens E6 has a negative focal power, the object side surface S11 is a concave surface, and the image side surface S12 is a concave surface. The filter E7 has an object side surface S13 and an image side surface S14, and the image sensor CCD protection lens E8 has an object side surface S15 and an image side surface S16. Light from an object passes through the surfaces S1 to S16 in sequence and is finally imaged on the imaging surface S17.

[0058] Table 7 shows the surface type, the radius of curvature, the thickness, and the material of each lens of the optical imaging lens of Example 4, wherein the units of the radius of curvature and the thickness are millimeters (mm).

[0059] Table 7

[0060] In Table 7, the object side surface and the image side surface of each of the first lens E1, the second lens E2, the third lens E3, the fourth lens E4, the fifth lens E5, and the sixth lens E6 are Q-type aspheric surfaces, and the surface type of each aspheric lens can be defined by, but is not limited to, the following aspheric surface formula:

[0061] wherein Z is the distance from a corresponding point on the aspheric surface to a plane tangent to the vertex of the surface, r is the radial coordinate of the aspheric surface, c is the curvature of the vertex of the aspheric surface, K is the conic coefficient, a m is the aspheric coefficient, r max is the maximum radial radius coordinate, and u = r / r max . Table 8 shows the conic coefficient and the high-order coefficients A4, A6, A8, A10, A12, A14, A16, A18, A20, A22, A24, A26, A28, and A30 of each aspheric surface that can be used in the fourth embodiment.

[0062] Table 8

[0063] In the examples 1-4, the basic data are as follows: Table 9

[0064] In the examples 1-4, the respective conditions are as follows: Table 10

[0065] A camera module at least comprises an optical lens, and the optical lens is internally mounted with the imaging optical system, the imaging optical system is configured by selecting six plastic aspheric lenses, and the refractive power and surface shape of each lens are reasonably configured, so that the optical lens can have the characteristics of small aperture, large field of view, high relative luminance and high resolution, and the total length of the lens is short, and the lens is lighter than the glass lens, so as to meet the needs of compactness and lightness.

[0066] The above is one or more embodiments provided in combination with specific content, and it is not intended that the specific implementation of the present application is limited to these descriptions. Any approximation, similarity or replacement of the method, structure, etc. of the present application, or any technical deduction or replacement under the premise of the concept of the present application, should be considered as the protection scope of the present application.

Claims

1. An imaging optical system, characterized in that: Along the optical axis from the object plane to the image plane, it consists of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, and a sixth lens in sequence; The first lens has negative optical power, and its object side is flat while its image side is concave. The second lens has positive optical power and its object-side surface is convex. The third lens has optical power; The fourth lens has positive optical power, and its object side is convex, as is its image side; The fifth lens has positive optical power and its image-side surface is convex. The sixth lens has negative optical power and its object side is concave. The imaging optical system satisfies the following relationship: 0.7 < |f2 / R3| < 2.1; 1.2 < (R7-R8) / (R7+R8) < 3.6; Where f2 is the focal length of the second lens, R3 is the radius of curvature of the image side of the second lens, R7 is the radius of curvature of the object side of the fourth lens, and R8 is the radius of curvature of the image side of the fourth lens.

2. The imaging optical system according to claim 1, characterized in that: The imaging optical system satisfies the following relationship: 1.2 < |f2 / f1| < 2.3; 0.7 < |f3-f4| / |f3+f4| < 3.0; Where f2 is the focal length of the second lens, f1 is the focal length of the first lens, f3 is the focal length of the third lens, and f4 is the focal length of the fourth lens.

3. The imaging optical system according to claim 1, characterized in that: The imaging optical system satisfies the following relationship: 1.8 < |f123 / f456| < 3.6; 1.5 < |f56 / f| < 3.5; Where f123 is the combined focal length of the first, second and third lenses, f456 is the combined focal length of the fourth, fifth and sixth lenses, f56 is the combined focal length of the fifth and sixth lenses, and f is the effective focal length of the entire optical system.

4. The imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 10.0mm < (FNO*f*IMGH) / DT11 < 12.5mm; Wherein, FNO is the F-number of the optical imaging lens, f is the effective focal length of the imaging optical system, IMGH is half the diagonal length of the effective pixel area on the imaging surface of the optical system, and DT11 is half the maximum effective light transmission radius of the object side of the first lens.

5. The imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 8.0 < (tan(HFOV)*TTL) / IMGH < 11.2; Where HFOV is half of the maximum field of view of the imaging optical system, TTL is the on-axis distance from the object side of the first lens to the imaging surface, and IMGH is half the diagonal length of the effective pixel area on the imaging surface of the optical system.

6. The imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 2.4 < (CT1+CT2) / T12 < 4.7; Wherein, CT1 is the center thickness of the first lens on the optical axis, CT2 is the center thickness of the second lens on the optical axis, and T12 is the axial distance from the image side of the first lens to the object side of the second lens.

7. The imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system satisfies the following relationship: 2.4 < ΣCT / ΣAT < 3.5; Wherein, ΣCT is the sum of the center thicknesses of the first lens, second lens, third lens, fourth lens, fifth lens, and sixth lens on the optical axis, and ΣAT is the sum of the axial distances from the image side of the first lens to the object side of the second lens, from the image side of the second lens to the object side of the third lens, from the image side of the third lens to the object side of the fourth lens, from the image side of the fourth lens to the object side of the fifth lens, and from the image side of the fifth lens to the object side of the sixth lens.

8. The imaging optical system according to any one of claims 1-3, characterized in that: The imaging optical system has an F-number ≤ 6, an overall length ≤ 4.7 mm, a lens diameter ≤ 2 mm, and a field of view ≥ 140°.

9. The imaging optical system according to any one of claims 1-3, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens, and the sixth lens are all aspherical lenses.

10. A camera module, comprising at least an optical lens, characterized in that: The optical lens is equipped with an imaging optical system according to any one of claims 1-9.

Images