An inner focusing micro single fixed focus lens

Abstract

The 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 sequence along an optical axis from an object side to an image side, and 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 arranged in sequence along the optical axis from the object side to the image side; the second lens group comprises an eighth lens, a ninth lens, a tenth lens and an eleventh lens arranged in sequence along the optical axis from the object side to the image side; the third lens group comprises a twelfth lens and a thirteenth lens arranged in sequence along the optical axis from the object side to the image side; and the fourth lens group comprises a fourteenth lens. The embodiment of the 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 type micro-single fixed focus lens.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and more particularly to an internal focusing mirrorless fixed-focus lens. Background Technology

[0002] With the development of technology, the market demand for mirrorless cameras continues to expand, leading to diverse needs for lenses with different focal lengths, apertures, focusing methods, and price points. Mirrorless prime lenses emphasize their large aperture advantage, which produces a shallow depth of field, highlighting the subject and creating a soft background blur effect, suitable for portrait and still life photography. At the same time, prime lenses typically have higher resolution and contrast, resulting in excellent image quality. However, mirrorless lenses from mainstream manufacturers are often expensive in China, making them a high barrier to entry for most ordinary consumers. Summary of the Invention

[0003] This invention provides an internally focused mirrorless fixed-focus lens to achieve a 14mm focal length, large aperture, high resolution, full-frame mirrorless short-focus lens, thereby reducing the cost of focusing mirrorless fixed-focus lenses.

[0004] This invention provides an internal focusing mirrorless fixed-focus lens, comprising 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 along the optical axis from the object side to the image side, wherein the third lens group is a focusing lens group.

[0005] 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;

[0006] 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;

[0007] 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;

[0008] The fourth lens group includes the fourteenth lens.

[0009] Optionally, 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.

[0010] 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.

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

[0012] The fourteenth lens has positive optical power;

[0013] The fixed-focus lens also includes an aperture stop, which is located between the seventh lens and the eighth lens.

[0014] Optionally, at least one of the following relations must be 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 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.

[0019] Optionally, the following relation is satisfied:

[0020] -0.193≤Φ1 / F1≤-0.036;

[0021] -0.091≤Φ2 / F1≤-0.020;

[0022] 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.

[0023] Optionally, the following relation 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 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.

[0027] Optionally, the following relation is satisfied:

[0028] 7.198≤TTL / EFL≤10.080;

[0029] 0.117≤BFL / TTL≤0.335;

[0030] 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.

[0031] Optionally, 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.

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

[0033] Optionally, the following relation 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 relation 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 plane of the fixed-focus lens.

[0041] This invention provides an internally focusing mirrorless fixed-focus lens that meets the imaging requirements of high resolution and low distortion while maintaining low cost and small size. By allocating the number of lenses in the lens group and rationally distributing the optical power of each lens group, an internally focusing mirrorless fixed-focus lens with a focal length of 14mm, an imaging target area of ​​43.2mm, and an f-number of approximately 1.9 is achieved. At its widest aperture, the MTF value of all fields of view reaches ≥0.5 at a spatial frequency of 30lp / mm while achieving |distortion| ≤10%. Transverse chromatic aberration is also corrected. In short, this invention provides a 14mm focal length, large aperture, high resolution, full-frame mirrorless short-focus lens, reducing the cost of focusing mirrorless fixed-focus lenses. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the infinity-distance lens in Embodiment 1 of the present invention;

[0043] Figure 2 The MTF diagram of the infinity-point lens in Example 1;

[0044] Figure 3 This is a field curvature curve diagram of the lens at infinity distance in Example 1;

[0045] Figure 4 This is a distortion curve diagram of the lens at infinity object distance in Example 1;

[0046] Figure 5 This is a chromatic aberration diagram of the lens at infinity object distance in Example 1;

[0047] Figure 6 This is a schematic diagram of the infinity-point lens in Example 2;

[0048] Figure 7 The MTF chart of the infinity-point lens in Example 2;

[0049] Figure 8 This is a field curvature curve diagram of the lens at infinity distance in Example 2;

[0050] Figure 9 This is a distortion curve diagram of the lens at infinity distance in Example 2;

[0051] Figure 10 This is the transverse chromatic aberration diagram of the lens at infinity object distance in Example 2;

[0052] Figure 11 This is a schematic diagram of the infinity-point lens in Example 3;

[0053] Figure 12 The MTF chart of the infinity-point lens in Example 3;

[0054] Figure 13 This is a field curvature curve diagram of the lens at infinity distance in Example 3;

[0055] Figure 14 This is a distortion curve diagram of the lens at infinity distance in Example 3;

[0056] Figure 15 This is a chromatic aberration diagram of the lens at infinity object distance in Example 3. Detailed Implementation

[0057] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0058] Example 1

[0059] Figure 1 This is a schematic diagram of the infinity-point lens in Embodiment 1 of the present invention; see reference. Figure 1 The internal focusing mirrorless fixed-focus lens includes a first lens group G1 with positive optical power, a second lens group G2 with positive optical power, a third lens group G3 with negative optical power, and a fourth lens group G4 with positive optical power, arranged sequentially from the object side to the image side along the optical axis. The third lens group G3 is the focusing lens group.

[0060] The first lens group G1 includes 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 arranged sequentially from the object side to the image side along the optical axis; the second lens group G2 includes an eighth lens L8, a ninth lens L9, a tenth lens L10, and an eleventh lens L11 arranged sequentially from the object side to the image side along the optical axis; the third lens group G3 includes a twelfth lens L12 and a thirteenth lens L13 arranged sequentially from the object side to the image side along the optical axis; and the fourth lens group G4 includes a fourteenth lens L14.

[0061] This invention provides an internally focusing mirrorless fixed-focus lens that meets the imaging requirements of high resolution and low distortion while maintaining low cost and small size. By allocating the number of lenses in the lens group and rationally distributing the optical power of each lens group, an internally focusing mirrorless fixed-focus lens with a focal length of 14mm, an imaging target area of ​​43.2mm, and an f-number of approximately 1.9 is achieved. At its widest aperture, the MTF value of all fields of view reaches ≥0.5 at a spatial frequency of 30lp / mm while achieving |distortion| ≤10%. Transverse chromatic aberration is also corrected. In short, this invention provides a 14mm focal length, large aperture, high resolution, full-frame mirrorless short-focus lens, reducing the cost of focusing mirrorless fixed-focus lenses.

[0062] For example, 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 embodiments of the present invention adopt an all-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. The fixed-focus lens also includes an aperture stop STO, which is located between the seventh lens L7 and the eighth lens L8. In this embodiment of the invention, the optical power of each lens is further rationally allocated.

[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; where 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. Decreasing the optical power of a lens group increases its focusing movement; increasing the optical power of a lens group decreases its focusing movement. Satisfying these requirements allows for a reduction in the overall length of the fixed-focus lens. The system distortion is the sum of the distortions produced by all lenses. This distortion can be balanced by limiting the optical power of each lens before and after the aperture stop STO. 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, and 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 relationships: -0.193≤Φ1 / F1≤-0.036; -0.091≤Φ2 / F1≤-0.020; where 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. By satisfying these relationships and reasonably controlling 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, the field of view can be expanded in conjunction with the first lens L1. This ensures that the maximum field of view (FOV) of the fixed-focus lens can satisfy: FOV≥120°. This disperses the large field of view light entering the fixed-focus lens to the rear of the optical system, which is beneficial for reducing lens distortion in conjunction with the first lens L1. Furthermore, it effectively smooths out the incident angle of light, which is beneficial for correcting higher aberrations and improving the resolution of the fixed-focus lens.

[0066] Optionally, the fixed-focus lens satisfies the following relationships: 0.479≤(R1-R2) / (R1+R2)≤0.560; 0.000≤CT1 / (R1-R2)≤0.060; where R1 represents the radius of curvature of the object-side side of the first lens L1, i.e., R1 represents the radius of curvature of the object-side side of the first lens L1. R2 represents the radius of curvature of the image-side side of the first lens L1, i.e., R2 represents the radius of curvature of the image-side side of the first lens L1. CT1 represents the center thickness of the first lens L1 along the optical axis. By controlling the ratio of the sum of the radius of curvature of the object-side side and the radius of curvature of the image-side side of the first lens L1 to the center thickness of the first lens L1 along the optical axis within this range, it is beneficial to constrain the lens shape of the first lens L1, avoid the lens shape of the first lens L1 being too curved, and facilitate the processing and shaping of the first lens L1.

[0067] Optionally, the prime lens satisfies the following relationships: 7.198 ≤ TTL / EFL ≤ 10.080; 0.117 ≤ BFL / TTL ≤ 0.335; where TTL represents the total optical length of the prime lens, EFL represents the optical power of the prime lens, and BFL represents the optical back focal length of the prime lens. Satisfying these relationships ensures that the prime lens meets optical performance requirements while significantly reducing its size and improving its compatibility.

[0068] Optionally, the fixed-focus lens includes at least three aspherical glass lenses, wherein both the first lens group G1 and the third lens group G3 include at least one aspherical glass lens. Aspherical glass lenses effectively correct geometric aberrations in fixed-focus lenses.

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

[0070] Optionally, the fixed-focus lens satisfies the following relationships: 80.00≤Vd1≤96.00; 45.00≤Vd2≤60.00; 30.00≤Vd3≤45.00; where 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 beneficial for reducing the size of zoom lenses.

[0071] Optionally, a fixed-focus lens satisfies the following relationship: -0.398 ≤ DIS / HI ≤ 0.217; where DIS represents the optical distortion of the fixed-focus lens, and HI represents the maximum image plane of the fixed-focus lens. Meeting these requirements ensures that the distortion of the fixed-focus lens is very small, without affecting its imaging performance.

[0072] For example, seven lenses are arranged before the aperture stop STO and seven lenses are arranged after the aperture stop STO. The third lens L3 and the fourth lens L4 form a cemented lens group, the fifth lens L5 and the sixth lens L6 form a cemented lens group, and the eighth lens L8 and the ninth lens L9 form a cemented lens group.

[0073] For example, the fixed-focus lens may further include a low-pass filter CG, which is located on the side of the fourteenth lens L14 away from the first lens L1 and on the side of the fourteenth lens L14 near the image plane. This serves to protect the image sensor chip in the imaging sensor and to achieve low-pass filtering. The image sensor chip is used to convert the light signals collected by the lens into electrical signals, thereby ensuring the imaging effect of the lens.

[0074] Table 1. Design values ​​for a fixed-focus lens in Example 1.

[0075]

[0076]

[0077] Table 1 shows one design value for the fixed-focus lens in Embodiment 1. The specific values ​​can be adjusted according to product requirements and are not intended to limit the embodiments of the present invention. The fixed-focus lens shown in Table 1 can be... Figure 1As shown. A lens generally consists of two surfaces, each of which is a refractive surface. The surface numbers in Table 1 are assigned according to the surfaces of each lens. Surface number 1 represents the front surface (object side) of the first lens L1, surface number 2 represents the rear surface (image side) of the first lens L1, and so on, which will not be elaborated further here. The radius of curvature represents the degree of curvature of the lens surface. A positive radius of curvature value indicates that the center of curvature is on the side of the surface closer to the image plane IMA, i.e., a positive value means that the surface bends towards the image plane IMA; a negative radius of curvature value indicates that the center of curvature is on the side of the surface farther from the image plane IMA, i.e., a negative value means that the surface bends towards the object plane. "INF" in the radius of curvature column indicates that the surface is flat and the radius of curvature is infinite, in mm. The value in the thickness column represents the central axial distance between the current surface and the next surface, in mm. The refractive index column represents the refractive index of the medium between the current surface and the next surface, representing the ability of the material between the current surface and the next surface to deflect light. The blank space in the refractive index column represents the refractive index of air, which is 1. The Abbe number represents the dispersion characteristics of light by the material between the current surface and the next surface; a blank space indicates that the current location is air.

[0078] For example, an aspherical lens (including a glass aspherical lens) satisfies the following formula:

[0079]

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

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

[0082]

[0083] The "Surface Number" column in Table 2 has the same meaning as the "Surface Number" column in Table 1. In the embodiments of this invention, "E" represents a base-10 exponent.

[0084] It's important to note that even with a prime lens, to match different object distances and ensure that objects at different distances are clearly imaged on the image sensor, the image distance must be dynamically adjusted by moving the lens elements (focusing lens group). Unlike zoom lenses, prime lenses do not have a zoom lens group, and prime lenses achieve internal focusing.

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

[0086] Image plane size (mm) Φ43.2 Focal length (mm) 13.997 Total optical length (mm) 127.64 F / # 1.90 Field of view (°) 117.1

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

[0088] Figure 2 This is the MTF (Mean Transmission Function) plot for the infinity-distance lens in Example 1; the horizontal axis represents the spatial frequencies of line pairs in object space imaged onto the image plane by the optical system, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trends in the optical transfer function of the image in the meridional and sagittal directions at different fields of view as the spatial frequency increases. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of light rays at all positions are less than the wave phase aberration caused by the physical limitations of the system itself, and can be ignored. Figure 2 It can be seen that the optical transfer function of this system is high at 30 lp / mm for each field of view, and the trend change is gentle and smooth. This indicates that the optical system can achieve the imaging requirements of high resolution and uniform image quality.

[0089] Figure 3 This is a field curvature curve diagram of the lens at infinity object distance in Example 1; the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; from Figure 3 It can be seen that the lens provided in this embodiment has effectively controlled field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small.

[0090] Figure 4 This is a distortion curve diagram of the lens at infinity object distance in Example 1; the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, which has no unit; from Figure 4 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0091] Figure 5 This is the transverse chromatic aberration diagram for the infinity-distance lens in Example 1; the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertex in the transverse direction represents the maximum pupil radius; the dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 5 It can be seen that the axial aberrations of different wavelengths (0-1.0 normalized aperture) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of the lens is well controlled.

[0092] Example 2

[0093] Similarities to the above embodiments will not be repeated here.

[0094] Table 4. One design value for a fixed-focus lens in Example 2.

[0095]

[0096]

[0097] Table 4 shows one design value for the fixed-focus lens in Embodiment 2. The specific values ​​can be adjusted according to product requirements and are not intended to limit the embodiments of the present invention. The fixed-focus lens shown in Table 4 can be... Figure 6 As shown in the image.

[0098] Table 5 Aspherical coefficients of the fixed-focus lens in Example 2

[0099]

[0100] The meaning of the "Surface Number" column in Table 5 is consistent with that in Table 4. In the embodiments of this invention, "E" represents a base-10 exponent.

[0101] Table 6. Specific parameters of the fixed-focus lens in Example 2.

[0102] Image plane size (mm) Φ43.2 Focal length (mm) 13.983 Total optical length (mm) 125.19 F / # 1.91 Field of view (°) 110.1

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

[0104] Figure 7 This is the MTF (Mean Transmission Function) plot for the infinity-distance lens in Example 2; the horizontal axis represents the spatial frequencies of line pairs in object space imaged onto the image plane by the optical system, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trends in the optical transfer function of the image in the meridional and sagittal directions at different fields of view as the spatial frequency increases. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of light rays at all positions are less than the wave phase aberrations caused by the physical limitations of the system itself, and can be ignored. Figure 7 It can be seen that the optical transfer function of this system is high at 30 lp / mm for each field of view, and the trend change is gentle and smooth. This indicates that the optical system can achieve the imaging requirements of high resolution and uniform image quality.

[0105] Figure 8 This is a field curvature curve diagram of the lens at infinity object distance in Example 2; the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; from Figure 8 It can be seen that the lens provided in this embodiment has effectively controlled field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small.

[0106] Figure 9 This is a distortion curve diagram of the lens at infinity object distance in Example 2; the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, without units; from Figure 9 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0107] Figure 10 This is the transverse chromatic aberration diagram for the infinity-distance lens in Example 2; the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertex in the transverse direction represents the maximum pupil radius; the dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 10 It can be seen that the axial aberrations of different wavelengths (0-1.0 normalized aperture) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of the lens is well controlled.

[0108] Example 3

[0109] Similarities to the above embodiments will not be repeated here.

[0110] Table 7. One design value for a fixed-focus lens in Example 3.

[0111]

[0112]

[0113] Table 7 shows one design value for the fixed-focus lens in Embodiment 3. The specific values ​​can be adjusted according to product requirements and are not intended to limit the embodiments of the present invention. The fixed-focus lens shown in Table 7 can be... Figure 11 As shown in the image.

[0114] Table 8 Aspherical coefficients of the fixed-focus lens in Example 3

[0115]

[0116]

[0117] The meaning of the "Face Number" column in Table 8 is consistent with that in Table 7. In the embodiments of this invention, "E" represents a base-10 exponent.

[0118] Table 9. Specific parameters of the fixed-focus lens in Example 3

[0119] Image plane size (mm) Φ43.2 Focal length (mm) 14.984 Total optical length (mm) 122.15 F / # 1.91 Field of view (°) 118.6

[0120] As shown in Table 9, the maximum diameter of the image plane that a fixed-focus lens can achieve is 43.2 mm, the focal length of a fixed-focus lens is 14.984 mm, the total optical length of a fixed-focus lens is 122.15 mm, the F number is 1.91, and the field of view is 118.6°.

[0121] Figure 12 This is the MTF (Mean Transmission Function) plot for the infinity-distance lens in Example 3; the horizontal axis represents the spatial frequencies of line pairs in object space imaged onto the image plane by the optical system, and the vertical axis represents the magnitude of the optical transfer function. Different curves represent the trends in the optical transfer function of the image in the meridional and sagittal directions at different fields of view as the spatial frequency increases. The ideal curve is a straight line coinciding with the system's diffraction limit, indicating that the geometric aberrations of light rays at all positions are less than the wave phase aberration caused by the physical limitations of the system itself, and can be ignored. Figure 12 It can be seen that the optical transfer function of this system is high at 30 lp / mm for each field of view, and the trend change is gentle and smooth. This indicates that the optical system can achieve the imaging requirements of high resolution and uniform image quality.

[0122] Figure 13 This is a field curvature curve diagram of the lens at infinity object distance in Example 3; the horizontal axis represents the magnitude of the field curvature in mm; the vertical axis represents the normalized image height, which has no unit; where T represents the meridion and S represents the sagitta; from Figure 13 It can be seen that the lens provided in this embodiment has effectively controlled field curvature, that is, during imaging, the difference between the image quality in the center and the image quality in the periphery is small.

[0123] Figure 14 This is a distortion curve diagram of the lens at infinity object distance in Example 3; the horizontal axis represents the magnitude of distortion, in %; the vertical axis represents the normalized image height, without units; from Figure 14 As can be seen, the distortion of the lens provided in this embodiment has been well corrected, and the imaging distortion is small.

[0124] Figure 15 This is the transverse chromatic aberration diagram for the infinity-distance lens in Example 3; the vertical direction represents the normalized aperture, 0 indicates on the optical axis, and the vertex in the transverse direction represents the maximum pupil radius; the dominant wavelength is 546nm, and the horizontal direction represents the offset relative to the dominant wavelength, in millimeters (mm). Figure 15 It can be seen that the axial aberrations of different wavelengths (0-1.0 normalized aperture) are all controlled within a reasonable range, indicating that the transverse chromatic aberration of the lens is well controlled.

[0125] Table 10 Parameter design values ​​for each embodiment

[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 description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, combinations, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended 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; 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.

2. 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.

3. 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.

4. 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 on the image side, and CT1 represents the center thickness of the first lens on the optical axis.

5. 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.

6. 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.

7. The fixed-focus lens according to claim 6, characterized in that, The second lens, the seventh lens, and the thirteenth lens are glass aspherical lenses.

8. The fixed-focus lens according to claim 7, 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.

9. 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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