Internal focusing type micro-single prime lens

Abstract

The invention provides an internal focusing type micro-single prime lens, which comprises a first lens group with positive focal power, a second lens group with positive focal power, a third lens group with negative focal power and a fourth lens group with positive focal power which are sequentially arranged from an object space to an image space along an optical axis, and is characterized in that the third lens group is a focusing lens group; the first lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged from the object space to the image space along the optical axis; the second lens group comprises an eighth lens, a ninth lens, a tenth lens and an eleventh lens which are sequentially arranged from the object space to the image space along the optical axis; the third lens group comprises a twelfth lens and a thirteenth lens which are sequentially arranged from the object space to the image space along the optical axis; the fourth lens group includes a fourteenth lens. According to the embodiment of the invention, a large-aperture, high-resolution and full-frame micro-single short-focus lens with a focal length of 14 mm is realized, and the cost of a focusing micro-single fixed-focus lens is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical lens, in particular to an inner focusing type micro single fixed focus lens. BACKGROUND

[0002] With the development of science and technology, the market demand of micro single camera is expanding, and there are various demands for lenses with different focal lengths, different apertures, different focusing modes, different prices, etc. Micro single fixed focus lens emphasizes its large aperture advantage. Large aperture can produce shallow depth of field, highlight the main body and create a soft background blur effect, which is suitable for portrait and still photography. At the same time, fixed focus lens usually has higher resolution and contrast, which can bring excellent image quality. However, the micro single lenses of mainstream micro single lens manufacturers on the market are usually expensive in domestic market, and most ordinary consumers have high threshold to start photography. SUMMARY

[0003] The embodiment of the present application provides an inner focusing type micro single fixed focus lens, so as to realize a focal length of 14mm, a large aperture, a high resolution and a full-frame micro single short focus lens, and reduce the cost of the focusing type micro single fixed focus lens.

[0004] The embodiment of the present application provides an inner focusing type micro single fixed focus lens, which comprises a first lens group with positive refractive power, a second lens group with positive refractive power, a third lens group with negative refractive power and a fourth lens group with positive refractive power arranged in order along the optical axis from the object side to the image side, and the third lens group is a focusing lens group.

[0005] The first lens group comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in order along the optical axis from the object side to the image side.

[0006] The second lens group comprises an eighth lens, a ninth lens, a tenth lens and an eleventh lens arranged in order along the optical axis from the object side to the image side.

[0007] The third lens group comprises a twelfth lens and a thirteenth lens arranged in order along the optical axis from the object side to the image side.

[0008] The fourth lens group comprises a fourteenth lens.

[0009] Optionally, the first lens has negative refractive power, the second lens has negative refractive power, the third lens has negative refractive power, the fourth lens has positive refractive power, the fifth lens has negative refractive power, the sixth lens has positive refractive power, and the seventh lens has positive refractive power.

[0010] The eighth lens has negative refractive power, the ninth lens has positive refractive power, the tenth lens has positive refractive power, and the eleventh lens has positive refractive power.

[0011] the twelfth lens has positive refractive power, and the thirteenth lens has negative refractive power;

[0012] the fourteenth lens has positive refractive power;

[0013] The fixed focus lens further comprises a stop, which is located between the seventh lens and the eighth lens.

[0014] Optionally, at least one of the following relationships is satisfied:

[0015] -10.906≤F1 / F3≤-8.451;

[0016] -0.589≤F2 / F3≤-0.450;

[0017] -5.140≤F4 / F3≤-4.731;

[0018] wherein F1 represents the refractive power of the first lens group, F2 represents the refractive power of the second lens group, F3 represents the refractive power of the third lens group, and F4 represents the refractive power of the fourth lens group.

[0019] Optionally, the following relationship is satisfied:

[0020] -0.193≤Φ1 / F1≤-0.036;

[0021] -0.091≤Φ2 / F1≤-0.020;

[0022] wherein F1 represents the refractive power of the first lens group, Φ1 represents the refractive power of the first lens, and Φ2 represents the refractive power of the second lens.

[0023] Optionally, the following relationship is satisfied:

[0024] 0.479≤(R1-R2) / (R1+R2)≤0.560;

[0025] 0.000≤CT1 / (R1-R2)≤0.060;

[0026] wherein R1 represents the radius of curvature of the object side surface of the first lens, R2 represents the radius of curvature of the image side surface of the first lens L1, and CT1 represents the central thickness of the first lens on the optical axis.

[0027] Optionally, the following relationship is satisfied:

[0028] 7.198≤TTL / EFL≤10.080;

[0029] 0.117≤BFL / TTL≤0.335;

[0030] wherein TTL represents an optical total length of the fixed focus lens, EFL represents an optical power of the fixed focus lens, and BFL represents an optical back focus of the fixed focus lens.

[0031] Optionally, at least three glass aspherical lenses are included, wherein the first lens group and the third lens group each include at least one glass aspherical lens.

[0032] Optionally, the second lens, the seventh lens and the thirteenth lens are the glass aspherical lenses.

[0033] Optionally, the following relationship is satisfied:

[0034] 80.00≤Vd1≤96.00;

[0035] 45.00≤Vd2≤60.00;

[0036] 30.00≤Vd3≤45.00;

[0037] wherein Vd1 represents the Abbe number of the second lens, Vd2 represents the Abbe number of the seventh lens, and Vd3 represents the Abbe number of the thirteenth lens.

[0038] Optionally, the following relationship is satisfied:

[0039] -0.398≤DIS / HI≤0.217;

[0040] wherein DIS represents the optical distortion of the fixed focus lens, and HI represents the maximum image surface of the fixed focus lens.

[0041] The embodiment of the present application provides an inner focusing type micro single fixed focus lens, which meets the imaging requirements of high resolution and low distortion under the premise of ensuring low cost and small size. Through the number distribution of each lens in the lens group and the reasonable distribution of the optical power of each lens group, an inner focusing type micro single fixed focus lens with a focal length of 14 mm, an imaging target surface of 43.2 mm and an F number of about 1.9 is realized. Under full aperture, the MTF value of all fields reaches above 0.5 at a spatial frequency of 30 lp / mm while realizing |distortion|≤10%. The sagittal chromatic aberration is corrected. In short, the embodiment of the present application realizes a focal length of 14 mm, a large aperture, a high resolution, a full-frame micro single short focus lens, and reduces the cost of the focusing type micro single fixed focus lens. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 Fig. 1 is a structural schematic diagram of an infinity focus lens in the embodiment of the present application;

[0043] Figure 2 Fig. 1 is an MTF diagram of the infinity focus lens in the embodiment of the present application;

[0044] Figure 3 Field curvature curve of the infinite- distance object lens in Example 1;

[0045] Figure 4 Distortion curve of the infinite- distance object lens in Example 1;

[0046] Figure 5 Vignetting curve of the infinite- distance object lens in Example 1;

[0047] Figure 6 Structure schematic diagram of the infinite- distance object lens in Example 2;

[0048] Figure 7 MTF diagram of the infinite- distance object lens in Example 2;

[0049] Figure 8 Field curvature curve of the infinite- distance object lens in Example 2;

[0050] Figure 9 Distortion curve of the infinite- distance object lens in Example 2;

[0051] Figure 10 Vignetting curve of the infinite- distance object lens in Example 2;

[0052] Figure 11 Structure schematic diagram of the infinite- distance object lens in Example 3;

[0053] Figure 12 MTF diagram of the infinite- distance object lens in Example 3;

[0054] Figure 13 Field curvature curve of the infinite- distance object lens in Example 3;

[0055] Figure 14 Distortion curve of the infinite- distance object lens in Example 3;

[0056] Figure 15 Vignetting curve of the infinite- distance object lens in Example 3. DETAILED DESCRIPTION

[0057] The application will be further described below in conjunction with the drawings and examples. It should be understood that the specific examples described herein are intended to be illustrative only and are not intended to limit the scope of the present application. In addition, it should be noted that only the parts related to the present application are shown in the drawings for the purpose of description.

[0058] Example 1

[0059] Figure 1 Structure schematic diagram of the infinite- distance object lens in Example 1;Figure 1 The inner focusing micro-single fixed focus lens comprises, in order along the optical axis from the object side to the image side, a first lens group G1 with positive refractive power, a second lens group G2 with positive refractive power, a third lens group G3 with negative refractive power, and a fourth lens group G4 with positive refractive power, and the third lens group G3 is a focusing lens group.

[0060] The first lens group G1 comprises, in order along the optical axis from the object side to the image side, a first lens L1, a second lens L2, a third lens L3, a fourth lens L4, a fifth lens L5, a sixth lens L6, and a seventh lens L7; the second lens group G2 comprises, in order along the optical axis from the object side to the image side, an eighth lens L8, a ninth lens L9, a tenth lens L10, and an eleventh lens L11; the third lens group G3 comprises, in order along the optical axis from the object side to the image side, a twelfth lens L12 and a thirteenth lens L13; and the fourth lens group G4 comprises a fourteenth lens L14.

[0061] The embodiment of the present application provides an inner focusing micro-single fixed focus lens, which meets the imaging requirements of high resolution and low distortion under the premise of ensuring low cost and small size. Through the number distribution of each lens in the lens group and the reasonable distribution of the refractive power of each lens group, the inner focusing micro-single fixed focus lens with a focal length of 14 mm, an imaging target surface of 43.2 mm, and an F number of about 1.9 is realized. Under full aperture, the MTF values of all fields reach above 0.5 at a spatial frequency of 30 lp / mm, while |distortion|≤10%. The sagittal chromatic aberration is corrected. In short, the embodiment of the present application realizes a micro-single short focus lens with a focal length of 14 mm, a large aperture, high resolution, and a full-frame, and reduces the cost of the focusing micro-single fixed focus lens.

[0062] Exemplarily, the first lens L1, the second lens L2, the third lens L3, the fourth lens L4, the fifth lens L5, the sixth lens L6, the seventh lens L7, the eighth lens L8, the ninth lens L9, the tenth lens L10, the eleventh lens L11, the twelfth lens L12, the thirteenth lens L13, and the fourteenth lens L14 are glass lenses, and the embodiment of the present application adopts a full-glass structure.

[0063] Optionally, the first lens L1 has negative optical power, the second lens L2 has negative optical power, the third lens L3 has negative optical power, the fourth lens L4 has positive optical power, the fifth lens L5 has negative optical power, the sixth lens L6 has positive optical power, the seventh lens L7 has positive optical power, the eighth lens L8 has negative optical power, the ninth lens L9 has positive optical power, the tenth lens L10 has positive optical power, the eleventh lens L11 has positive optical power, the twelfth lens L12 has positive optical power, the thirteenth lens L13 has negative optical power, and the fourteenth lens L14 has positive optical power.

[0064] Optionally, the fixed focus lens satisfies at least one of the following relationships: -10.906≤F1 / F3≤-8.451; -0.589≤F2 / F3≤-0.450; -5.140≤F4 / F3≤-4.731; wherein F1 represents the optical power of the first lens group G1, F2 represents the optical power of the second lens group G2, F3 represents the optical power of the third lens group G3, and F4 represents the optical power of the fourth lens group G4. The optical power of the lens group decreases, and the focusing movement increases. The optical power of the lens group increases, and the focusing movement decreases. The above requirements can compress the total length of the fixed focus lens. The system distortion is the sum of the distortion of all lenses. By limiting the optical power of each lens before and after the stop STO, the distortion can be balanced. The optical power of each lens before the stop STO is reflected in the limitation of the optical power of the first lens group G1. The optical power of each lens before the stop STO is reflected in the limitation of the optical power of the second lens group G2, the third lens group G3, and the fourth lens group G4.

[0065] Optionally, the fixed focus lens satisfies the following relationship: -0.193≤Φ1 / F1≤-0.036; -0.091≤Φ2 / F1≤-0.020; wherein F1 represents the optical power of the first lens group G1, Φ1 represents the optical power of the first lens L1, and Φ2 represents the optical power of the second lens L2. The above relationship satisfies the reasonable control of the ratio of the optical power of the first lens L1 and the second lens L2 to the optical power of the first lens group G1, which can expand the field of view angle together with the first lens L1. The maximum field of view angle FOV of the fixed focus lens can satisfy: FOV≥120°. The large field of view light entering the fixed focus lens is diverged to the rear of the optical system, which is beneficial to reduce the lens distortion together with the first lens L1, and can effectively flatten the incident angle of the light, which is beneficial to correct high-order aberration and improve the resolution of the fixed focus lens.

[0066] Optionally, the fixed focus lens satisfies the following relationship: 0.479≤(R1-R2) / (R1+R2)≤0.560; 0.000≤CT1 / (R1-R2)≤0.060; wherein R1 represents the curvature radius of the surface of the first lens L1 close to the object side, that is, R1 represents the curvature radius of the object side surface of the first lens L1. R2 represents the curvature radius of the surface of the first lens L1 close to the image side, R2 represents the curvature radius of the image side surface of the first lens L1. CT1 represents the central thickness of the first lens L1 on the optical axis. By controlling the ratio of the sum of the curvature radius of the object side surface of the first lens L1 and the curvature radius of the image side surface of the first lens L1 to the central thickness of the first lens L1 on the optical axis in the range, the lens shape of the first lens L1 is constrained, avoiding the lens shape of the first lens L1 being too curved, and the processing and molding of the first lens L1 are facilitated.

[0067] Optionally, the fixed focus lens satisfies the following relationship: 7.198≤TTL / EFL≤10.080; 0.117≤BFL / TTL≤0.335; wherein TTL represents the total optical length of the fixed focus lens, EFL represents the focal length of the fixed focus lens, and BFL represents the optical back focal length of the fixed focus lens. Satisfying the above relationship makes the fixed focus lens meet the optical performance requirements while ensuring that the lens volume can be greatly reduced and the compatibility of the fixed focus lens is improved.

[0068] Optionally, the fixed focus lens comprises at least three glass aspherical lenses, wherein the first lens group G1 and the third lens group G3 each comprise at least one glass aspherical lens. The glass aspherical lens has a good correction effect on the geometric aberration of the fixed focus lens

[0069] Optionally, the second lens L2, the seventh lens L7 and the thirteenth lens L13 are glass aspherical lenses. The second lens L2 and the seventh lens L7 are lenses in the first lens group G1, and the first lens group G1 comprises two glass aspherical lenses. The thirteenth lens L13 is a lens in the third lens group G3, and the third lens group G3 comprises one glass aspherical lens.

[0070] Optionally, the fixed focus lens satisfies the following relationship: 80.00≤Vd1≤96.00; 45.00≤Vd2≤60.00; 30.00≤Vd3≤45.00; wherein Vd1 represents the Abbe number of the second lens L2, Vd2 represents the Abbe number of the seventh lens L7, and Vd3 represents the Abbe number of the thirteenth lens L13. This is conducive to compressing the volume of the zoom lens.

[0071] Optionally, the fixed focus lens satisfies the following relationship: -0.398≤DIS / HI≤0.217; wherein, DIS represents optical distortion of the fixed focus lens, and HI represents the maximum image surface of the fixed focus lens. By satisfying the above requirement, the distortion of the fixed focus lens is small, and meanwhile, the imaging effect of the fixed focus lens is not affected.

[0072] Exemplarily, 7 lenses are arranged before the diaphragm STO, and 7 lenses are arranged after the diaphragm STO. The third lens L3 and the fourth lens L4 form a set of cemented lenses, the fifth lens L5 and the sixth lens L6 form a set of cemented lenses, and the eighth lens L8 and the ninth lens L9 form a set of cemented lenses.

[0073] Exemplarily, the fixed focus lens can further include a low-pass filter CG, the low-pass filter CG is located on the side of the fourteenth lens L14 away from the first lens L1, and the low-pass filter CG is located on the side of the fourteenth lens L14 close to the image surface, so as to protect the photosensitive chip in the imaging sensor and realize the function of low-pass filtering. The photosensitive chip is used to convert the light signal collected by the lens into an electric signal, thereby ensuring the imaging effect of the lens.

[0074] Table 1 shows a design value of the fixed focus lens in Example 1

[0075]

[0076]

[0077] Table 1 shows a design value of the fixed focus lens in Example 1, and the specific numerical value can be adjusted according to product requirements, which is not a limitation of the embodiments of the present application. The fixed focus lens shown in Table 1 can be Figure 1The lens generally includes two surfaces, each of which is a refractive surface. The surface numbers in Table 1 are numbered according to the surfaces of each lens. Among them, surface number 1 represents the front surface (i.e. the object side surface) of the first lens L1, surface number 2 represents the rear surface (i.e. the image side surface) of the first lens L1, and the like, which will not be described here. The radius of curvature represents the bending degree of the lens surface. A positive radius of curvature value indicates that the center of curvature is on the side of the surface close to the image plane IMA, i.e. a positive value represents that the surface is bent towards the image plane IMA; a negative radius of curvature value indicates that the center of curvature is on the side of the surface away from the image plane IMA, i.e. a negative value represents that the surface is bent towards the object plane. "INF" in the column of radius of curvature represents that the surface is a plane, and the radius of curvature is infinite, with the unit of mm. The numerical value in the column of thickness represents the central axial distance from the current surface to the next surface, with the unit of mm. The refractive index in the column represents the refractive index of the medium between the current surface and the next surface, which represents the deflection ability of the material between the current surface and the next surface to the light. The space in the column of refractive index represents the refractive index of air, and the refractive index of air is 1. The Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to the light, and the space represents that the current position is air.

[0078] Exemplarily, the aspheric lens (including the glass aspheric lens) satisfies the following formula:

[0079]

[0080] Wherein, z is the axial distance of the curved surface at a position with a height of r perpendicular to the optical axis to the vertex of the surface, i.e. the axial height of the aspheric Z direction, r is the height of the aspheric surface; c represents the curvature at the vertex of the aspheric surface, which is the reciprocal of the radius of curvature in value; k is the fitting conic coefficient; A, B, C, D, E, F are the fourth-order, sixth-order, eighth-order, tenth-order, twelfth-order and fourteenth-order high-order aspheric coefficients of the aspheric surface.

[0081] Table 2 aspheric coefficients of the fixed focus lens in Example 1

[0082]

[0083] The meaning of the column of "surface number" in Table 2 is consistent with that of the column of "surface number" in Table 1. "E" in each embodiment of the present application represents the base-10 exponent.

[0084] It should be noted that even if it is a fixed focus lens, in order to match different object distances and ensure that objects at different object distances can be clearly imaged on the photosensitive chip, the image distance must be dynamically adjusted by moving the lens (focusing lens group). Unlike zoom lenses, fixed focus lenses do not have a variable magnification lens group, and the fixed focus lens realizes internal focusing.

[0085] Table 3 specific parameters of the fixed focus lens in Example 1

[0086] Image surface size (mm) Φ 43.2 Focal length (mm) 13.997 Optical total length (mm) 127.64 F / # 1.90 Field angle (°) 117.1

[0087] As shown in Table 3, the maximum diameter of the image surface of the fixed focus lens is 43.2 mm, the focal length of the fixed focus lens is 13.997 mm, the total optical length of the fixed focus lens is 127.64 mm, the F number is 1.90, and the field of view angle is 117.1°.

[0088] Figure 2 The MTF graph of the infinity object distance lens in Example 1 is shown in FIG. 2. The horizontal coordinate represents the spatial frequency of the image of the line pair distributed on the image surface after the optical system is imaged, and the vertical coordinate represents the modulus of the optical transfer function. Different curves represent the change trend of the optical transfer function of the image in the meridional and sagittal directions with the increase of the spatial frequency. The most ideal curve is a straight line coinciding with the system diffraction limit, which indicates that the geometric aberration of the light at all positions is smaller than the wave aberration of the system itself caused by physical limitations, which can be ignored. It can be seen from FIG. 2 that the optical transfer function of the system is relatively high at 30 lp / mm, and the trend changes smoothly. It indicates that the optical system can realize high resolution and uniform imaging quality. Figure 2

[0089] Figure 3 The field curvature curve of the infinity object distance lens in Example 1 is shown in FIG. 3. The horizontal coordinate represents the size of the field curvature, and the unit is mm. The vertical coordinate represents the normalized image height without unit. T represents the meridional direction, and S represents the sagittal direction. Figure 3 It can be seen that the lens provided in the embodiment is effectively controlled in the field curvature, that is, the difference between the central image quality and the peripheral image quality is small during imaging.

[0090] Figure 4 The distortion curve of the infinity object distance lens in Example 1 is shown in FIG. 4. The horizontal coordinate represents the size of the distortion, and the unit is %. The vertical coordinate represents the normalized image height without unit. Figure 4 It can be seen that the distortion of the lens provided in the embodiment is well corrected, and the imaging distortion is small.

[0091] Figure 5 The axial chromatic aberration graph of the infinity object distance lens in Example 1 is shown in FIG. 5. The vertical direction represents the normalized aperture, and 0 represents on the optical axis. The vertical direction top represents the maximum pupil radius. The main wavelength uses 546 nm, and the horizontal direction represents the offset of the relative main wavelength, and the unit is millimeter (mm). Figure 5 It can be seen that the axial image of the normalized aperture of different wavelengths 0-1.0 is controlled in a reasonable range, which indicates that the axial chromatic aberration of the lens is well controlled.

[0092] Example 2

[0093] ​Similarities with the above embodiments are not repeated here.

[0094] Table 4 shows a design value of the fixed focus lens in Example 2, which can be adjusted according to product requirements, and is not a limitation on the embodiments of the present application. The fixed focus lens shown in Table 4 can be

[0095]

[0096]

[0097] Table 4 shows a design value of the fixed focus lens in Example 2, which can be adjusted according to product requirements, and is not a limitation on the embodiments of the present application. The fixed focus lens shown in Table 4 can be Figure 6 as shown in Table 4.

[0098] Table 5 shows the aspheric coefficients of the fixed focus lens in Example 2.

[0099]

[0100] The meaning of the column of "surface number" in Table 5 is consistent with that of the column of "surface number" in Table 4. "E" in the embodiments of the present application represents the base-10 exponent.

[0101] Table 6 shows the specific parameters of the fixed focus lens in Example 2.

[0102] Image surface size (mm) Φ 43.2 Focal length (mm) 13.983 Optical total length (mm) 125.19 F / # 1.91 Field angle (°) 110.1

[0103] As shown in Table 6, the maximum diameter of the image surface of the fixed focus lens is 43.2 mm, the focal length of the fixed focus lens is 13.983 mm, the total optical length of the fixed focus lens is 125.19 mm, the F number is 1.91, and the field of view is 110.1°.

[0104] Figure 7 Figure 6 is an MTF diagram of the fixed focus lens in Example 2; the horizontal coordinate represents the spatial frequency of the line pair passing through the optical system and imaged on the image surface in the object space, and the vertical coordinate represents the modulus of the optical transfer function. Different curves represent the change trend of the optical transfer function of the image in the meridional and sagittal directions with the increase of the spatial frequency. The most ideal curve is a straight line coinciding with the system diffraction limit, indicating that the geometric aberration of the light at all positions is smaller than the wave aberration caused by the physical limitation of the system itself, which can be ignored. It can be known from Figure 7 that the optical transfer function of the system is relatively high at 30 lp / mm, and the trend changes smoothly. This indicates that the optical system can achieve high resolution and uniform imaging quality.

[0105] Figure 8 Figure 7 is a field curvature curve diagram of the fixed focus lens in Example 2; the horizontal coordinate represents the size of the field curvature, and the unit is mm; the vertical coordinate represents the normalized image height, and has no unit; T represents the meridional direction, and S represents the sagittal direction; it can be known fromFigure 8 It can be seen that the lens provided by the embodiment is effectively controlled in field curvature, i.e., the difference between the central image quality and the peripheral image quality is small when imaging.

[0106] Figure 9 The distortion curve of the infinite distance lens in the embodiment two is shown in FIG. 6, in which the horizontal coordinate represents the size of distortion in % and the vertical coordinate represents the normalized image height without unit. Figure 9 It can be seen that the distortion of the lens provided by the embodiment is well corrected, and the imaging distortion is small.

[0107] Figure 10 The sagittal chromatic aberration graph of the infinite distance lens in the embodiment two is shown in FIG. 7, in which the vertical direction represents the normalized aperture, 0 represents on the optical axis, the sagittal direction vertex represents the maximum pupil radius; the main wavelength uses 546 nm, the horizontal direction represents the offset of the relative main wavelength in millimeter (mm). It can be seen from FIG. 7 that the axial aberration of the normalized aperture of different wavelengths 0-1.0 is controlled in a reasonable range, which indicates that the sagittal chromatic aberration of the lens is well controlled. Figure 10 It can be seen that the axial aberration of the normalized aperture of different wavelengths 0-1.0 is controlled in a reasonable range, which indicates that the sagittal chromatic aberration of the lens is well controlled.

[0108] Embodiment three

[0109] The similar parts to the above embodiments are not repeated here.

[0110] Table 7 shows a design value of the fixed focus lens in the embodiment three, and the specific numerical value can be adjusted according to product requirements, which is not a limitation to the embodiment of the present application. The fixed focus lens shown in Table 7 can be shown in Table 1.

[0111]

[0112]

[0113] Table 7 shows a design value of the fixed focus lens in the embodiment three, and the specific numerical value can be adjusted according to product requirements, which is not a limitation to the embodiment of the present application. The fixed focus lens shown in Table 7 can be shown in Table 1. Figure 11

[0114] Table 8 shows the aspheric coefficients of the fixed focus lens in the embodiment three.

[0115]

[0116]

[0117] The meaning of the column of “surface number” in Table 8 is consistent with that of the column of “surface number” in Table 7. “E” in each embodiment of the present application represents the base-10 exponent.

[0118] Table 9 shows the specific parameters of the fixed focus lens in the embodiment three.

[0119] Image surface size (mm) Φ 43.2 Focal length (mm) 14.984 Optical total length (mm) 122.15 F / # 1.91 Field angle (°) 118.6

[0120] ​As shown in Table 9, the maximum diameter of the image surface of the fixed focus lens is 43.2 mm, the focal length of the fixed focus lens is 14.984 mm, the total optical length of the fixed focus lens is 122.15 mm, the F number is 1.91, and the field of view angle is 118.6°.

[0121] Figure 12 The MTF diagram of the infinite conjugate lens in Example Three is shown in FIG. 9. The horizontal coordinate represents the spatial frequency of the image of the line pair passing through the optical system and imaged on the image surface in the object space, and the vertical coordinate represents the modulus of the optical transfer function. Different curves represent the change trend of the optical transfer function of the image in the meridional and sagittal directions with the increase of the spatial frequency in different fields of view. The most ideal curve is a straight line coinciding with the system diffraction limit, indicating that the geometric aberration of the light at all positions is smaller than the wave aberration of the system itself physically limited and can be ignored. It can be seen from FIG. 9 that the optical transfer function of the system in each field of view is relatively high at 30 lp / mm, and the trend changes smoothly. It indicates that the optical system can realize high resolution and uniform imaging quality. Figure 12

[0122] Figure 13 The field curvature curve of the infinite conjugate lens in Example Three is shown in FIG. 10. The horizontal coordinate represents the size of the field curvature, and the unit is mm. The vertical coordinate represents the normalized image height without unit. T represents the meridional direction, and S represents the sagittal direction. It can be seen from FIG. 10 that the lens provided in the embodiment is effectively controlled in the field curvature, that is, the difference between the image quality at the center and the image quality at the periphery is small when imaging. Figure 13

[0123] Figure 14 The distortion curve of the infinite conjugate lens in Example Three is shown in FIG. 11. The horizontal coordinate represents the size of the distortion, and the unit is %. The vertical coordinate represents the normalized image height without unit. It can be seen from FIG. 11 that the distortion of the lens provided in the embodiment is well corrected, and the imaging distortion is small. Figure 14

[0124] Figure 15 The axial chromatic aberration diagram of the infinite conjugate lens in Example Three is shown in FIG. 12. The vertical direction represents the normalized aperture, and 0 represents on the optical axis. The vertical direction top represents the maximum pupil radius. The main wavelength uses 546 nm, and the horizontal direction represents the offset amount relative to the main wavelength, and the unit is millimeter (mm). It can be seen from FIG. 12 that the axial aberration of the normalized aperture of different wavelengths 0-1.0 is controlled within a reasonable range, indicating that the axial chromatic aberration of the lens is well controlled. Figure 15

[0125] Table 10: Parameter design values of each example

[0126] Parameter Example 1 Example 2 Example 3 F1 / F3 -10.088 -9.269 -9.718 F2 / F3 -0.576 -0.579 -0.582 F4 / F3 -4.868 -5.004 -4.915 Φ1 / F1 -0.155 -0.168 -0.174 Φ2 / F1 -0.077 -0.084 -0.081 (R1-R2) / (R1+R2) 0.530 0.533 0.506 CT1 / (R1-R2) 0.038 0.016 0.038 TTL / EFL 9.119 8.960 8.159 BFL / TTL 0.123 0.127 0.129 Vd1 89.45 93.58 91.53 Vd2 49.28 49.88 52.27 Vd3 38.22 39.85 38.16 DIS / HI -0.133 -0.193 0.012

[0127] ​​​​Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, modifications, combinations and substitutions can be made by those skilled in the art without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. An internally focusing mirrorless fixed-focus lens, characterized in that, It includes a first lens group with positive optical power, a second lens group with positive optical power, a third lens group with negative optical power, and a fourth lens group with positive optical power, arranged sequentially from the object side to the image side along the optical axis, wherein the third lens group is a focusing lens group; The first lens group includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventh lens arranged sequentially along the optical axis from the object side to the image side; The second lens group includes an eighth lens, a ninth lens, a tenth lens, and an eleventh lens arranged sequentially from the object side to the image side along the optical axis; The third lens group includes a twelfth lens and a thirteenth lens arranged sequentially from the object side to the image side along the optical axis; The fourth lens group includes the fourteenth lens.

2. The fixed-focus lens according to claim 1, characterized in that, The first lens has negative optical power, the second lens has negative optical power, the third lens has negative optical power, the fourth lens has positive optical power, the fifth lens has negative optical power, the sixth lens has positive optical power, and the seventh lens has positive optical power. The eighth lens has negative optical power, the ninth lens has positive optical power, the tenth lens has positive optical power, and the eleventh lens has positive optical power. The twelfth lens has positive optical power, and the thirteenth lens has negative optical power; The fourteenth lens has positive optical power; The fixed-focus lens also includes an aperture stop, which is located between the seventh lens and the eighth lens.

3. The fixed-focus lens according to claim 1, characterized in that, Satisfying at least one of the following relations: -10.906≤F1 / F3≤-8.451; -0.589≤F2 / F3≤-0.450; -5.140≤F4 / F3≤-4.731; Wherein, F1 represents the optical power of the first lens group, F2 represents the optical power of the second lens group, F3 represents the optical power of the third lens group, and F4 represents the optical power of the fourth lens group.

4. The fixed-focus lens according to claim 1, characterized in that, The following relationship must be satisfied: -0.193≤Φ1 / F1≤-0.036; -0.091≤Φ2 / F1≤-0.020; Wherein, F1 represents the optical power of the first lens group, Φ1 represents the optical power of the first lens, and Φ2 represents the optical power of the second lens.

5. The fixed-focus lens according to claim 1, characterized in that, The following relationship must be satisfied: 0.479≤(R1-R2) / (R1+R2)≤0.560; 0.000≤CT1 / (R1-R2)≤0.060; Wherein, R1 represents the radius of curvature of the first lens on the object side, R2 represents the radius of curvature of the first lens L1 on the image side, and CT1 represents the center thickness of the first lens on the optical axis.

6. The fixed-focus lens according to claim 1, characterized in that, The following relationship must be satisfied: 7.198≤TTL / EFL≤10.080; 0.117≤BFL / TTL≤0.335; Wherein, TTL represents the total optical length of the fixed-focus lens, EFL represents the optical power of the fixed-focus lens, and BFL represents the optical back focal length of the fixed-focus lens.

7. The fixed-focus lens according to claim 1, characterized in that, It includes at least three glass aspherical lenses, wherein the first lens group and the third lens group each include at least one glass aspherical lens.

8. The fixed-focus lens according to claim 7, characterized in that, The second lens, the seventh lens, and the thirteenth lens are glass aspherical lenses.

9. The fixed-focus lens according to claim 8, characterized in that, The following relationship must be satisfied: 80.00≤Vd1≤96.00; 45.00≤Vd2≤60.00; 30.00≤Vd3≤45.00; Wherein, Vd1 represents the Abbe number of the second lens, Vd2 represents the Abbe number of the seventh lens, and Vd3 represents the Abbe number of the thirteenth lens.

10. The fixed-focus lens according to claim 1, characterized in that, The following relationship must be satisfied: -0.398≤DIS / HI≤0.217; Wherein, DIS represents the optical distortion of the fixed-focus lens, and HI represents the maximum image plane of the fixed-focus lens.

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