Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The embodiment of the application provides a camera module, which comprises a lens barrel, an electronic photosensitive element and an optical system provided by the embodiment of the application, wherein a first lens, a second lens, a third lens and a fourth lens of the optical system and a prism are arranged in the lens barrel, the electronic photosensitive element is arranged at the image side of the optical system and is used for converting optical signals of objects which are incident on the electronic photosensitive element through the first lens, the prism, the second lens and the third lens into electric signals of images. The electron sensitive element may be a complementary metal oxide semiconductor (Complementary Metal Oxide Semiconductor, CMOS) or a Charge-coupled Device (CCD). The camera module can be an independent lens of a digital camera or an imaging module integrated on electronic equipment such as a smart phone. By installing the first lens to the seventh lens and the prism of the optical system in the camera module, the surface type and the refractive power of each lens of the first lens to the seventh lens are reasonably configured, so that the camera module provided by the embodiment of the application can realize structural miniaturization while meeting better remote shooting effect.
The embodiment of the application provides electronic equipment, which comprises a shell and a camera module provided by the embodiment of the application. The camera module and the electronic photosensitive element are arranged in the shell. The electronic device may be a smart phone, a Personal Digital Assistant (PDA), a tablet computer, a smart watch, an unmanned aerial vehicle, an electronic book reader, a vehicle recorder, a wearable device, etc. By arranging the camera module provided by the embodiment of the application in the electronic equipment, the electronic equipment can realize the miniaturization of the structure while meeting the better remote shooting effect.
The embodiment of the application provides an optical system, which sequentially comprises a first lens and a prism from an object side to an image side along a first optical axis direction, wherein the prism is used for turning an optical path to enable the optical path to have a first optical axis ① turned to a second optical axis ②, the first optical axis ① is intersected with the second optical axis ②, and the optical system sequentially comprises a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens from the object side to the image side along a second optical axis ② direction. In the first lens to the seventh lens, an air space may be provided between any adjacent two lenses.
Specifically, the specific shape and structure of the seven lenses are as follows:
The lens system includes a first lens element with positive refractive power having a convex object-side paraxial region and a planar first lens element with a convex image-side paraxial region, a second lens element with positive refractive power having a convex object-side paraxial region and a convex image-side paraxial region, a third lens element with refractive power having a concave object-side paraxial region, a fourth lens element with refractive power having a concave object-side paraxial region, a fifth lens element with refractive power having a negative refractive power, a sixth lens element with a convex object-side paraxial region and a concave image-side paraxial region, and a seventh lens element with negative refractive power. By reasonably configuring the surface type and the refractive power of each lens of the first lens to the seventh lens, the optical system can realize the miniaturization of the structure while meeting the better telephoto effect.
In one embodiment, at least one surface of at least one of the first to seventh lenses is aspherical. With this structure, the optical system can realize structural miniaturization while satisfying a good telephoto effect.
In one embodiment, the optical system satisfies the conditional expression 1.6< TTL/(ImgH 2) <2.5;11 DEG HFOV <16 DEG; 0.6< DL/TTL <0.8, wherein TTL is the distance from the object side surface of the second lens element to the imaging surface of the optical system on the second optical axis ②, imgH is half the diagonal length of the effective imaging area of the optical system on the imaging surface, HFOV is half the maximum field angle of the optical system, and DL is the distance from the object side surface of the second lens element to the image side surface of the seventh lens element on the second optical axis ②. When the optical system meets the above conditional expression, the second lens to the seventh lens are reasonably arranged, so that the ratio of the height of the lens to the imaging surface is in a smaller range, the optical system is miniaturized, and the space of the lens part is reduced on the basis of the miniaturization, thereby being beneficial to the arrangement of the module structure end.
In one embodiment, the optical system satisfies a conditional expression of 0.9< TTL/f <1.2, wherein TTL is a distance from an object side surface of the second lens to an imaging surface of the optical system on the second optical axis ②, and f is an effective focal length of the optical system. When the optical system satisfies the above conditional expression, a lower lens height can be provided in the range of HFOV <16 ° so that the optical system is more easily implanted in the portable device. Meanwhile, due to the use of the aspheric surface, the ratio of TTL to f is in a smaller numerical range, and under the condition of realizing telephoto and long-shot photography, the optical system is beneficial to balancing chromatic aberration, spherical aberration and other aberrations, so that good imaging quality is obtained.
In one embodiment, the optical system satisfies the conditional expression EFY (L2-L7) >10mm, wherein EFY (L2-L7) is the focal length of the rear lens group consisting of the second lens to the seventh lens. When the optical system meets the above conditional expression, namely, the focal power of the first lens and the rear lens group is reasonably configured, the light entering through the first lens group is effectively balanced and the generated aberration and the effective convergence of marginal light are corrected through the rear lens group, so that the optical system has better shooting and distant effects while ensuring the compactness and miniaturization of the optical system.
In one embodiment, the optical system satisfies the condition that T56/T67<0.25, wherein T56 is a distance between the image side surface of the fifth lens element and the object side surface of the sixth lens element on the second optical axis ②, and T67 is a distance between the image side surface of the sixth lens element and the object side surface of the seventh lens element on the second optical axis ②. When the optical system meets the above conditional expression, namely, the length dimension of the optical system can be effectively compressed by reasonably configuring the position relationship between the fifth lens and the sixth lens and the position relationship between the sixth lens and the seventh lens, the direction change of light entering the optical system is slowed down, and the stray light intensity is reduced.
In one embodiment, the optical system satisfies the conditional expression of |f2/f1| <0.3, wherein f1 is the effective focal length of the first lens and f2 is the effective focal length of the second lens. When the optical system meets the above conditions, that is, the sizes and the refractive powers of the first lens and the second lens are reasonably configured, the larger spherical aberration generated by the front lens group can be balanced, the overall resolution of the optical system is improved, the bending power configuration at the rear end of the optical system is controlled, the peripheral aberration correction of the optical system is enhanced, and meanwhile, the size compression is facilitated, so that the optical system is miniaturized.
In one embodiment, the optical system satisfies the conditional expression of V2-V4 >30, wherein V2 is the Abbe number of the second lens and V4 is the Abbe number of the fourth lens. When the optical system meets the above conditional expression, the abbe numbers of the second lens and the fourth lens are reasonably configured, which is favorable for chromatic aberration correction and performance guarantee of the optical system.
In a first embodiment of the present invention,
Referring to fig. 1a and 1b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens element L3 with negative refractive power has concave object-side surface S5 and concave image-side surface S6, and concave image-side surface S6 and concave image-side surface S3;
the fourth lens element L4 with positive refractive power has a concave object-side surface S7 near the axis, a convex object-side surface S7 near the circumference, a convex image-side surface S8 near the axis, and a concave image-side surface S8 near the circumference;
The fifth lens element L5 with negative refractive power has a convex object-side surface S9 at the paraxial region and the near-circumferential region, and a concave object-side surface S10 at the paraxial region and the near-circumferential region of the fifth lens element L5;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
the seventh lens element L7 with negative refractive power has a convex object-side surface S13 near the axis, a concave object-side surface S13 near the circumference, a concave image-side surface S14 near the axis, and a convex image-side surface S14 near the circumference.
Of the above-described first to seventh lenses L1 to L7, at least one lens is made of a first plastic material, and at least one lens is made of a second plastic material, wherein the first plastic material and the second plastic material are different in optical characteristics.
Further, the optical system includes a stop STO, an infrared filter L8, and an imaging surface S17. A stop STO is provided on a side of the second lens L2 remote from the third lens L3 for controlling the amount of light entering. In other embodiments, the stop STO may be disposed between two adjacent lenses, or on other lenses. The infrared filter L8 is disposed on the image side of the seventh lens L7, and includes an object side surface S15 and an image side surface S16, where the infrared filter L8 is configured to filter infrared light, so that the light incident on the imaging surface S17 is visible light, and the wavelength of the visible light is 380nm-780nm. The infrared filter L8 is made of glass and can be coated on the glass. S17 is an imaging surface of the optical system, and an area mapped to the effective pixel area of the electronic photosensitive element is an effective imaging area. It will be appreciated that the imaging surface overlaps but does not overlap with the electronic photosensitive element, and in one particular embodiment, the imaging surface in the cell phone is a circumscribed circle of the active pixel area.
Table 1a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 1a
Where f is the effective focal length of the optical system, FNO is the f-number of the optical system, FOV is the field angle of the optical system, TTL is the distance from the object side surface of the second lens element to the imaging surface of the optical system on the second optical axis ②, imgH is half the diagonal length of the effective imaging area of the optical system on the imaging surface, DL is the distance from the object side surface of the second lens element to the image side surface of the seventh lens element on the second optical axis ②.
In the present embodiment, at least one surface of at least one of the first lens L1 to the seventh lens L7 is an aspherical surface, and the surface shape x of each aspherical lens can be defined by, but not limited to, the following aspherical formula:
Where x is the distance vector height of the aspherical surface at a position h in the optical axis direction from the apex of the aspherical surface, c is the paraxial curvature of the aspherical surface, c=1/R (i.e., paraxial curvature c is the reciprocal of the radius R of Y in table 1a above), k is a conic coefficient, and Ai is the correction coefficient of the i-th order of the aspherical surface. Table 1b shows the higher order coefficients A4, A6, A8, A10, A12, A14, A16, A18 and A20 that can be used for each of the aspherical mirrors S1-S16 in the first embodiment.
TABLE 1b
Fig. 1b shows a longitudinal spherical aberration curve, an astigmatic curve and a distortion curve of the optical system of the first embodiment. The longitudinal spherical aberration curve represents the deviation of the converging focus of light rays with different wavelengths after passing through each lens of the optical system, the astigmatic curve represents meridian image surface bending and sagittal image surface bending, and the distortion curve represents distortion magnitude values corresponding to different field angles. As can be seen from fig. 1b, the optical system according to the first embodiment can achieve good imaging quality.
Second embodiment
Referring to fig. 2a and 2b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens element L3 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S5 of the third lens element L3 are concave, and the paraxial region and the near-circumferential region of the image-side surface S6 of the third lens element L3 are convex;
The fourth lens element L4 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S7 of the fourth lens element L4 are convex, and the paraxial region and the near-circumferential region of the image-side surface S8 of the fourth lens element L4 are concave;
The fifth lens element L5 with negative refractive power has a convex object-side surface S9 at the paraxial region and the near-circumferential region, and a concave object-side surface S10 at the paraxial region and the near-circumferential region of the fifth lens element L5;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
the seventh lens element L7 with negative refractive power has a convex object-side surface S13 near the axis, a concave object-side surface S13 near the circumference, a concave image-side surface S14 near the axis, and a convex image-side surface S14 near the circumference.
The other structures of the second embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 2a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 2a
The meaning of each parameter in table 2a is the same as that of each parameter in the first embodiment.
Table 2b gives the higher order coefficients that can be used for each aspherical mirror in the second embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.
TABLE 2b
Fig. 2b shows a longitudinal spherical aberration curve, an astigmatic curve and a distortion curve of the optical system of the second embodiment. As can be seen from fig. 2b, the optical system according to the second embodiment can achieve good imaging quality.
Third embodiment
Referring to fig. 3a and 3b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens element L3 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S5 of the third lens element L3 are concave, and the paraxial region and the near-circumferential region of the image-side surface S6 of the third lens element L3 are convex;
the fourth lens element L4 with positive bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S7 of the fourth lens element L4 are convex, and the paraxial region and the near-circumferential region of the image-side surface S8 of the fourth lens element L4 are concave;
The fifth lens element L5 with negative refractive power has a convex object-side surface S9 at the paraxial region and the near-circumferential region, and a concave object-side surface S10 at the paraxial region and the near-circumferential region of the fifth lens element L5;
The sixth lens element L6 with positive refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
The seventh lens L7 has a negative bending force, the object-side surface S13 of the seventh lens L7 is concave at the paraxial region and the near-circumferential region, and the image-side surface S14 of the seventh lens L7 is convex at the paraxial region and the near-circumferential region.
The other structures of the third embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 3a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 3a
The meaning of each parameter in table 3a is the same as that of each parameter in the first embodiment.
Table 3b gives the higher order coefficients that can be used for each of the aspherical mirror surfaces in the third embodiment, where each of the aspherical surface types can be defined by the formula given in the first embodiment.
TABLE 3b
Fig. 3b shows a longitudinal spherical aberration curve, an astigmatic curve and a distortion curve of the optical system of the third embodiment. As can be seen from fig. 3b, the optical system according to the third embodiment can achieve good imaging quality.
Fourth embodiment
Referring to fig. 4a and 4b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
the third lens L3 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S5 of the third lens L3 are concave, and the paraxial and the near-circumferential positions of the image side surface S6 of the third lens L3 are convex;
The fourth lens element L4 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S7 of the fourth lens element L4 are concave, the paraxial region of the image-side surface S8 of the fourth lens element L4 is convex, and the near-circumferential region of the image-side surface S8 is concave;
The fifth lens element L5 with positive refractive power has a concave object-side surface S9 at a paraxial region thereof, a convex object-side surface S9 at a paraxial region thereof, and a convex image-side surface S10 at a paraxial region thereof, wherein the concave image-side surface S10 at a paraxial region thereof;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
the seventh lens element L7 with negative refractive power has a convex object-side surface S13 near the axis, a concave object-side surface S13 near the circumference, a concave image-side surface S14 near the axis, and a convex image-side surface S14 near the circumference.
The other structures of the fourth embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 4a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 4a
The meaning of each parameter in table 4a is the same as that of each parameter in the first embodiment.
Table 4b gives the higher order coefficients that can be used for each aspherical mirror in the fourth embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.
TABLE 4b
Fig. 4b shows a longitudinal spherical aberration curve, an astigmatic curve and a distortion curve of the optical system of the fourth embodiment. As can be seen from fig. 4b, the optical system according to the fourth embodiment can achieve good imaging quality.
Fifth embodiment
Referring to fig. 5a and 5b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens element L3 with negative refractive power has concave object-side surface S5 and concave image-side surface S6, and concave image-side surface S6 and concave image-side surface S3;
the fourth lens element L4 with positive refractive power has a concave object-side surface S7 near the axis, a convex object-side surface S7 near the circumference, a convex image-side surface S8 near the axis, and a concave image-side surface S8 near the circumference;
The fifth lens element L5 with negative refractive power has a concave object-side surface S9 at a paraxial region thereof, a convex object-side surface S9 at a paraxial region thereof, and a convex image-side surface S10 at a paraxial region thereof, wherein the concave image-side surface S10 at a paraxial region thereof;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
the seventh lens element L7 with negative refractive power has a convex object-side surface S13 near the axis, a concave object-side surface S13 near the circumference, a concave image-side surface S14 near the axis, and a convex image-side surface S14 near the circumference.
The other structures of the fifth embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 5a shows a table of characteristics of the optical system of the present embodiment in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 5a
The meaning of each parameter in table 5a is the same as that of each parameter in the first embodiment.
Table 5b gives the higher order coefficients that can be used for each of the aspherical mirror surfaces in the fifth embodiment, where each of the aspherical surface types can be defined by the formula given in the first embodiment.
TABLE 5b
Fig. 5b shows a longitudinal spherical aberration curve, an astigmatic curve and a distortion curve of the optical system of the fifth embodiment. As can be seen from fig. 5b, the optical system according to the fifth embodiment can achieve good imaging quality.
Sixth embodiment
Referring to fig. 6a and 6b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens element L3 with negative refractive power has concave object-side surface S5 and concave image-side surface S6, and concave image-side surface S6 and concave image-side surface S3;
The fourth lens element L4 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S7 of the fourth lens element L4 are convex, and the paraxial region and the near-circumferential region of the image-side surface S8 of the fourth lens element L4 are concave;
the fifth lens element L5 with positive refractive power has a convex object-side surface S9 at a paraxial region and a near-circumferential region, and a convex image-side surface S10 at a paraxial region and a concave image-side surface S10 at a near-circumferential region, respectively;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
The seventh lens element L7 has a negative refractive power, wherein the object-side surface S13 of the seventh lens element L7 has concave surfaces at the paraxial region and the near-circumferential region, the image-side surface S14 of the seventh lens element L7 has concave surfaces at the paraxial region, and the image-side surface S14 has convex surfaces at the near-circumferential region.
The other structures of the sixth embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 6a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 6a
The meaning of each parameter in table 6a is the same as that of each parameter in the first embodiment.
Table 6b gives the higher order coefficients that can be used for each aspherical mirror in the sixth embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.
TABLE 6b
Fig. 6b shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the sixth embodiment. As can be seen from fig. 6b, the optical system according to the sixth embodiment can achieve good imaging quality.
Seventh embodiment
Referring to fig. 7a and 7b, the optical system of the present embodiment includes, in order from an object side to an image side along an optical axis:
the first lens L1 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S1 of the first lens L1 are convex, and the paraxial and the near-circumferential positions of the image side surface S2 of the first lens L1 are plane;
a prism Lp for turning over the optical path;
the second lens L2 has positive bending force, the paraxial and the near-circumferential positions of the object side surface S3 of the second lens L2 are convex, and the paraxial and the near-circumferential positions of the image side surface S4 of the second lens L2 are convex;
The third lens L3 has negative bending force, the paraxial and the near-circumferential positions of the object side surface S5 of the third lens L3 are concave surfaces, and the paraxial and the near-circumferential positions of the image side surface S6 of the third lens L3 are concave surfaces;
The fourth lens element L4 with negative bending force, wherein the paraxial region and the near-circumferential region of the object-side surface S7 of the fourth lens element L4 are convex, and the paraxial region and the near-circumferential region of the image-side surface S8 of the fourth lens element L4 are concave;
The fifth lens element L5 with positive refractive power has a convex object-side surface S9 at the paraxial region and the near-circumferential region, and a concave object-side surface S10 at the paraxial region and the near-circumferential region of the fifth lens element L5;
The sixth lens element L6 with negative refractive power, wherein the object-side surface S11 of the sixth lens element L6 is convex at the paraxial region and the near-circumferential region, and the image-side surface S12 of the sixth lens element L6 is concave at the paraxial region and the near-circumferential region;
The seventh lens L7 has a negative bending force, the object-side surface S13 of the seventh lens L7 is concave at the paraxial region and the near-circumferential region, and the image-side surface S14 of the seventh lens L7 is convex at the paraxial region and the near-circumferential region.
The other structures of the seventh embodiment are the same as those of the first embodiment, and reference is made thereto.
Table 7a shows a table of characteristics of the optical system of the present embodiment, in which data of focal length is obtained using light having a wavelength of 555nm, data of refractive index and dispersion coefficient is obtained using light having a wavelength of 587.56nm, and units of curvature radius and thickness are millimeters (mm).
TABLE 7a
The meaning of each parameter in table 7a is the same as that of each parameter in the first embodiment.
Table 7b gives the higher order coefficients that can be used for each aspherical mirror in the seventh embodiment, where each aspherical mirror profile can be defined by the formula given in the first embodiment.
TABLE 7b
Fig. 7b shows a longitudinal spherical aberration curve, an astigmatic curve, and a distortion curve of the optical system of the seventh embodiment. As can be seen from fig. 7b, the optical system according to the seventh embodiment can achieve good imaging quality.
Table 8 shows the values of TTL/(imgh×2), HFOV, DL/TTL, TTL/f, EFY (L2-L7), T56/T67, |f2/f1|, and|v2—v4| for the optical systems of the first to seventh embodiments.
TABLE 8
| TTL/(ImgH*2) | HFOV(°) | DL/TTL | TTL/f |
| First embodiment | 1.990456714 | 13.3 | 0.659246575 | 0.947283049 |
| Second embodiment | 2.010906612 | 13.3 | 0.674576271 | 0.962479608 |
| Third embodiment | 2.060327198 | 13.1 | 0.675765095 | 0.971084337 |
| Fourth embodiment | 1.954669393 | 15.2 | 0.721011334 | 1.071962617 |
| Fifth embodiment | 2.099522836 | 12.6 | 0.666396104 | 0.955779674 |
| Sixth embodiment | 2.109747785 | 12.6 | 0.684975767 | 0.961926962 |
| Seventh embodiment | 1.862644853 | 15 | 0.719121683 | 1.002752294 |
| EFY(L2~L7)(mm) | T56/T67 | |f2/f1| | |V2-V4| |
| First embodiment | 15.74 | 0.140785592 | 0.089818061 | 34.61 |
| Second embodiment | 15.52 | 0.18738194 | 0.085389998 | 34.61 |
| Third embodiment | 15.14 | 0.186302972 | 0.078322455 | 34.61 |
| Fourth embodiment | 12.36 | 0.138018458 | 0.072255703 | 34.61 |
| Fifth embodiment | 12.6 | 0.090736713 | 0.091149281 | 34.61 |
| Sixth embodiment | 16.47 | 0.089362322 | 0.09386172 | 34.61 |
| Seventh embodiment | 13.08 | 0.099603401 | 0.097745095 | 34.61 |
As can be seen from Table 8, each example satisfies the following conditional expression ：1.6<TTL/(ImgH*2)<2.5、11°<HFOV<16°、0.6<DL/TTL<0.8、0.9<TTL/f<1.2、EFY(L2～L7)>10mm、T56/T67<0.25、|f2/f1|<0.3、|V2-V4|>30.
The technical features of the above embodiments may be arbitrarily combined, and in order to make the description brief, all possible combinations of the technical features of the above embodiments are not described, however, as long as there is no contradiction between the combinations of the technical features, it should be considered as the scope of the description.
The foregoing examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.