Internal focusing type full-frame micro-single prime lens

Abstract

The embodiment of the utility model discloses an internal focusing type full-frame micro-single prime lens. The prime lens comprises four lens groups, and the focal power is negative, positive, negative and positive. The first lens group comprises five lenses with negative focal power, negative focal power, negative focal power, negative focal power and positive focal power, the second lens group comprises six lenses with positive focal power, negative focal power, positive focal power, positive focal power, positive focal power and negative focal power, the third lens group comprises one lens with negative focal power, and the fourth lens group comprises two lenses with positive focal power and negative focal power; the diaphragm is disposed between the second lens group and the third lens group. In conclusion, the focusing type prime lens design with the focal length being 24 mm, the imaging target surface being 43.2 mm and the F number being 2.0 can be achieved, and under the condition that the aperture is fully opened, MTF values of all view fields reach 0.6 or above at the spatial frequency being 30 lp / mm, and distortion is smaller than or equal to 1%. And the vertical axis chromatic aberration is corrected.

Description

Technical Field

[0001] The embodiments of the present utility model relate to the technical field of optical lenses, and particularly to an internal focusing full-frame mirrorless fixed-focus lens. Background Art

[0002] With the development of photography technology and the upgrading of camera technology, mirrorless cameras are favored by more consumers due to their light weight, convenient operation, and high image quality. The mirrorless lens market has thus started to expand and grow. In China, with the continuous development of society, there are also more and more photography enthusiasts in the country. However, currently, the mainstream mirrorless lens manufacturers in the market, such as Sony, Panasonic, Canon, Nikon, etc. are all foreign manufacturers, and the mirrorless lenses of mainstream manufacturers are often expensive in China, making it very difficult for most ordinary consumers to enter the field of photography. The present utility model patent has developed a full-frame mirrorless short-focus lens with a focal length of 24mm, a large aperture, and high image quality to meet the needs of domestic consumers and reduce the economic threshold for domestic photography enthusiasts. Content of the Utility Model

[0003] The present utility model provides an internal focusing full-frame mirrorless fixed-focus lens, which realizes the design of a focusing fixed-focus lens with a focal length of 24mm, an imaging target surface of 43.2mm, and an F-number of 2.0 through the combination of lens materials and the reasonable distribution of the optical power of each element.

[0004] The embodiments of the present utility model provide an internal focusing full-frame mirrorless fixed-focus lens, which includes a first lens with a negative optical power, a second lens with a negative optical power, a third lens with a negative optical power, a fourth lens with a negative optical power, a fifth lens with a positive optical power, an aperture stop, a sixth lens with a positive optical power, a seventh lens with a negative optical power, an eighth lens with a positive optical power, a ninth lens with a positive optical power, a tenth lens with a positive optical power, an eleventh lens with a negative optical power, a twelfth lens with a negative optical power, a thirteenth lens with a positive optical power, and a fourteenth lens with a negative optical power, which are arranged in sequence along the optical axis from the object side to the image side;

[0005] The first lens, the second lens, the third lens, the fourth lens, and the fifth lens form a first lens group with a negative total optical power;

[0006] The sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, and the eleventh lens form a second lens group with a positive total optical power;

[0007] The twelfth lens forms a third lens group with a negative total optical power;

[0008] The thirteenth lens and the fourteenth lens form a fourth lens group with a positive total optical power.

[0009] Optionally, each lens group satisfies the following conditions:

[0010] 0.462 ≤ F1 / F3 ≤ 0.615;

[0011] -0.452 ≤ F2 / F3 ≤ -0.407;

[0012] -24.136 ≤ F4 / F3 ≤ -1.163;

[0013] Wherein, F1 is the total optical power of the first lens group, F2 is the total optical power of the second lens group, F3 is the total optical power of the third lens group, and F4 is the total optical power of the fourth lens group.

[0014] Optionally, the first lens to the fourteenth lens are all glass lenses.

[0015] Optionally, the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the thirteenth lens, and the fourteenth lens are spherical lenses;

[0016] The eleventh lens and the twelfth lens are aspherical lenses.

[0017] Optionally, the first lens satisfies the following condition: 3.085 ≤ (R1 + R2) / (R1 - R2) ≤ 4.046;

[0018] Wherein, R1 is the radius of curvature of the side of the first lens close to the object, and R2 is the radius of curvature of the side of the first lens close to the image.

[0019] Optionally, the first lens satisfies the following condition: 0.319 ≤ U1 / F1 ≤ 0.445;

[0020] Wherein, U1 is the optical power of the first lens, and F1 is the total optical power of the first lens group.

[0021] Optionally, the first lens and the second lens satisfy the following conditions: Vd1 ≥ 95; Vd2 ≥ 95;

[0022] Wherein, Vd1 is the Abbe number of the first lens, and Vd2 is the Abbe number of the second lens.

[0023] Optionally, the third lens group satisfies the following condition: -1.214 ≤ SI / F3 ≤ -0.658;

[0024] Wherein, F3 is the total optical power of the third lens group, and SI is the distance from the diaphragm aperture to the image plane.

[0025] Optionally, the fixed-focus lens satisfies the following condition: -1.181 ≤ EXPP / HI ≤ -1.051;

[0026] Wherein, EXPP is the distance from the exit pupil plane of the fixed-focus lens to the image plane, and HI is the maximum image plane of the fixed-focus lens.

[0027] Optionally, the fixed-focus lens satisfies the following condition: -0.229 ≤ DIS / HI ≤ 0.153;

[0028] Wherein, HI is the maximum image plane of the fixed-focus lens, and DIS is the optical distortion of the fixed-focus lens.

[0029] In the technical solution of the embodiment of the present invention, by dividing the fourteen lenses of the fixed-focus lens into four lens groups, and adjusting the lens groups inside the lens, namely the second lens group and the third lens group, internal focusing can be achieved. That is, even when the lens length remains unchanged, rapid autofocus can be realized. In addition, the optical powers of the four lens groups are distributed as negative, positive, negative, and positive. Moreover, the optical powers of the five lenses in the first lens group are distributed as negative, negative, negative, negative, and positive, the optical powers of the six lenses in the second lens group are distributed as positive, negative, positive, positive, positive, and negative, the optical power of the one lens in the third lens group is distributed as negative, and the optical powers of the two lenses in the fourth lens group are distributed as positive and negative. Through the cooperation of the optical powers of the fourteen lenses in the four lens groups, while achieving a short focal length, high resolution is ensured and high image quality is realized. In addition, the aperture is arranged between the fifth lens and the sixth lens, that is, between the second lens group and the third lens group. Essentially, it is to limit the specific position of the aperture at the waist of the entire optical system, so as to precisely control the light passing amount, expand the ray height of the central chief ray at the aperture position, expand the aperture, ensure the light amount passing through the aperture, and ensure the imaging brightness; in addition, the aperture can block off-axis rays, effectively reduce off-axis aberrations, and ensure the imaging clarity. Description of the Drawings

[0030] Figure 1 is a schematic structural diagram of an internal focusing full-frame mirrorless fixed-focus lens provided by Embodiment 1 of the present invention at an infinite object distance;

[0031] Figure 2 is Figure 1 the MTF curve graph of the resolution of the shown fixed-focus lens;

[0032] Figure 3 is Figure 1 the field curvature and distortion curve graph of the shown fixed-focus lens;

[0033] Figure 4 is Figure 1Vertical chromatic aberration curve graph of the shown fixed-focus lens;

[0034] Figure 5 It is a schematic structural diagram of an internal focusing full-frame mirrorless fixed-focus lens provided in the second embodiment of the present invention at an infinite object distance;

[0035] Figure 6 Is Figure 5 Resolution MTF curve graph of the shown fixed-focus lens;

[0036] Figure 7 Is Figure 5 Field curvature and distortion curve graph of the shown fixed-focus lens;

[0037] Figure 8 Is Figure 5 Vertical chromatic aberration curve graph of the shown fixed-focus lens;

[0038] Figure 9 It is a schematic structural diagram of an internal focusing full-frame mirrorless fixed-focus lens provided in the third embodiment of the present invention at an infinite object distance;

[0039] Figure 10 Is Figure 9 Resolution MTF curve graph of the shown fixed-focus lens;

[0040] Figure 11 Is Figure 9 Field curvature and distortion curve graph of the shown fixed-focus lens;

[0041] Figure 12 Is Figure 9 Vertical chromatic aberration curve graph of the shown fixed-focus lens. Detailed implementation manners

[0042] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the accompanying drawings, rather than all the structures.

[0043] The terms used in the embodiments of the present utility model are for the purpose of describing specific embodiments only and are not intended to limit the present utility model. It should be noted that the orientation terms such as "upper", "lower", "left", and "right" described in the embodiments of the present utility model are described from the angles shown in the drawings and should not be construed as limiting the embodiments of the present utility model. In addition, in the context, it should also be understood that when it is mentioned that one element is formed "on" or "under" another element, it can not only be directly formed "on" or "under" another element, but also be indirectly formed "on" or "under" another element through an intermediate element. The terms "first", "second", etc. are only used for descriptive purposes and do not indicate any order, quantity, or importance, but are only used to distinguish different components. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to specific circumstances.

[0044] The term "comprising" and its variants used in the present utility model are open-ended, that is, "including but not limited to". The term "based on" is "at least partially based on". The term "an embodiment" means "at least one embodiment".

[0045] It should be noted that the concepts such as "first", "second", etc. mentioned in the present utility model are only used to distinguish the corresponding contents and are not used to limit the order or the interdependent relationship.

[0046] It should be noted that the modifications of "one" and "multiple" mentioned in the present utility model are illustrative rather than restrictive. Those skilled in the art should understand that unless clearly specified otherwise in the context, it should be understood as "one or more".

[0047] Figure 1 is a schematic structural diagram of an internal focusing full-frame mirrorless prime lens provided in the first embodiment of the present utility model at an infinite object distance. Refer to Figure 1 , the prime lens includes a first lens 101 with negative optical power, a second lens 102 with negative optical power, a third lens 103 with negative optical power, a fourth lens 104 with negative optical power, a fifth lens 105 with positive optical power, an aperture 500, a sixth lens 206 with positive optical power, a seventh lens 207 with negative optical power, an eighth lens 208 with positive optical power, a ninth lens 209 with positive optical power, a tenth lens 210 with positive optical power, an eleventh lens 211 with negative optical power, a twelfth lens 312 with negative optical power, a thirteenth lens 413 with positive optical power, and a fourteenth lens 414 with negative optical power, which are arranged in sequence along the optical axis from the object side to the image side;

[0048] The first lens 101, the second lens 102, the third lens 103, the fourth lens 104 and the fifth lens 105 form a first lens group 100 with a negative total optical power; the sixth lens 206, the seventh lens 207, the eighth lens 208, the ninth lens 209, the tenth lens 210 and the eleventh lens 211 form a second lens group 200 with a positive total optical power; the twelfth lens 312 forms a third lens group 300 with a negative total optical power; the thirteenth lens 413 and the fourteenth lens 414 form a fourth lens group 400 with a positive total optical power.

[0049] First of all, for an optical lens, the optical power is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, which characterizes the ability of the optical system to deflect light rays. The larger the absolute value of the optical power, the stronger the bending ability of the light rays; the smaller the absolute value of the optical power, the weaker the bending ability of the light rays. When the optical power is positive, the refraction of the light rays is convergent; when the optical power is negative, the refraction of the light rays is divergent. The optical power can be used to characterize a certain refracting surface of a lens (i.e., a surface of the lens), can be used to characterize a certain lens, or can be used to characterize a system formed by multiple lenses together (i.e., a lens group).

[0050] In the fixed-focus lens provided in this embodiment, each lens can be arranged in a lens barrel ( Figure 1 not shown in the figure), such as Figure 1As shown in the figure, in the embodiment of the present utility model, the fourteen lenses of the fixed-focus lens are divided into four lens groups. By adjusting the lens groups inside the lens, namely the second lens group 200 and the third lens group 300, internal focusing can be achieved. That is, even when the lens length remains unchanged, rapid autofocus can be realized. In addition, in the embodiment of the present utility model, the optical powers of the four lens groups are distributed as negative, positive, negative, and positive. Moreover, the optical powers of the five lenses in the first lens group are distributed as negative, negative, negative, negative, and positive, the optical powers of the six lenses in the second lens group 200 are distributed as positive, negative, positive, positive, positive, and negative, the optical power of the one lens in the third lens group 300 is distributed as negative, and the optical powers of the two lenses in the fourth lens group 400 are distributed as positive and negative. Essentially, it is the cooperation of the optical powers of the fourteen lenses in the four lens groups. While achieving a short focal length, it ensures a high resolution and high image quality. In addition, as known to those skilled in the art, the aperture in the optical system is used to limit the beam size and determines the amount of light entering the photosensitive element through the lens, that is, it is used to control the light passing amount of the lens. That is, the aperture directly determines the size of the aperture of the optical lens. The aperture 500 is arranged between the fifth lens 105 and the sixth lens 206, that is, between the second lens group 200 and the third lens group 300. Essentially, it is to limit the specific position of the aperture 500 at the waist of the entire optical system, so as to precisely control the light passing amount, expand the height of the central chief ray at the position of the aperture 500, expand the aperture, ensure the amount of light passing through the aperture 500, and ensure the imaging brightness. In addition, the aperture 500 can block off-axis light, effectively reducing off-axis aberrations and ensuring the clarity of the image.

[0051] In a specific embodiment, optionally, each lens group satisfies the following conditions:

[0052] 0.462 ≤ F1 / F3 ≤ 0.615;

[0053] -0.452 ≤ F2 / F3 ≤ -0.407;

[0054] -24.136 ≤ F4 / F3 ≤ -1.163;

[0055] Wherein, F1 is the total optical power of the first lens group 100, F2 is the total optical power of the second lens group 200, F3 is the total optical power of the third lens group 300, and F4 is the total optical power of the fourth lens group 400.

[0056] As is known to those skilled in the art, for an internal focusing fixed-focus lens, the smaller its optical power, the greater its focusing movement; conversely, the greater the optical power, the smaller the focusing movement. In this embodiment, by setting four lens groups to meet the above proportional range, internal focusing can be effectively achieved and the total length of the entire lens can be compressed. In addition, the distortion of the optical system is the sum of the distortions generated by all lenses. By restricting the optical powers of the lenses before and after the aperture, the distortion can be balanced.

[0057] In a specific embodiment, optionally, the first lens 101 to the fourteenth lens 414 are all glass lenses.

[0058] This embodiment adopts an all-glass structure. By matching the lens materials, the characteristics of the glass material can be utilized to reduce the temperature sensitivity of imaging, reduce the deformation degree of the lens at different temperatures, and ensure clear imaging in high and low temperature environments; at the same time, the focal length difference between visible light and infrared light of the overall lens can be reduced to ensure day and night confocal.

[0059] In a specific embodiment, optionally, the first lens 101, the second lens 102, the third lens 103, the fourth lens 104, the fifth lens 105, the sixth lens 206, the seventh lens 207, the eighth lens 208, the ninth lens 209, the tenth lens 210, the thirteenth lens 413, and the fourteenth lens 414 are spherical lenses; the eleventh lens 211 and the twelfth lens 312 are aspherical lenses.

[0060] In this embodiment, except for setting the eleventh lens 211 and the twelfth lens 312 as aspherical lenses, the remaining lenses are all set as spherical lenses. In essence, by matching spherical and aspherical lenses, the various aberrations of the lens are corrected by using the aspherical lenses to improve the image quality. In addition, since it is difficult to make an aspherical surface on glass, on the basis of using glass material, only two lenses are set as aspherical lenses, which can reduce the cost to a certain extent.

[0061] In a specific embodiment, optionally, the first lens 101 satisfies the following condition: 3.085 ≤ (R1 + R2) / (R1 - R2) ≤ 4.046; where R1 is the curvature radius of the side of the first lens 101 close to the object, and R2 is the curvature radius of the side of the first lens 101 close to the image.

[0062] In this embodiment, by setting the first lens 101 to meet the above conditions and restricting the specific shape of the first lens 101, it is beneficial to reduce the angle of the light entering the first lens 101.

[0063] In a specific embodiment, optionally, the first lens 101 satisfies the following condition: 0.319 ≤ U1 / F1 ≤ 0.445; where U1 is the optical power of the first lens 101, and F1 is the total optical power of the first lens group 100.

[0064] In this embodiment, by setting the optical powers of the first lens 101 and the first lens group 100, it is beneficial for the light rays of each field of view on the object side to enter the lens through the first lens 101, and then the spherical aberration is corrected jointly by the subsequent three lenses in this lens group.

[0065] In a specific embodiment, optionally, the first lens 101 and the second lens 102 satisfy the following conditions: Vd1 ≥ 95; Vd2 ≥ 95; where Vd1 is the Abbe number of the first lens 101, and Vd2 is the Abbe number of the second lens 102.

[0066] In this embodiment, setting the first lens 101 and the second lens 102 to satisfy the above Abbe number range essentially limits both the first lens 101 and the second lens 102 to be ED low-dispersion glasses, so as to utilize the ED low-dispersion glasses to play a good role in correcting the axial chromatic aberration and reducing the purple fringing phenomenon.

[0067] In a specific embodiment, optionally, the third lens group 300 satisfies the following condition: -1.214 ≤ SI / F3 ≤ -0.658; where F3 is the total optical power of the third lens group 300, and SI is the distance from the aperture stop to the image plane.

[0068] In this embodiment, setting the third lens group 300 to satisfy the above conditions aims to improve the angle at which the chief rays in the peripheral field of view enter the focusing lens group. When SI / F3 is less than -1.214, the distance from the aperture stop to the image plane will decrease, and the angle at which the chief rays in the peripheral field of view enter the focusing lens group will increase; while if SI / F3 is greater than -0.658, the distance from the aperture stop to the image plane will increase, and the angle at which the chief rays in the peripheral field of view enter the focusing lens group will decrease, which is not conducive to realizing the miniaturization of the lens.

[0069] In a specific embodiment, optionally, the fixed-focus lens satisfies the following condition: -1.181 ≤ EXPP / HI ≤ -1.051; where EXPP is the distance from the exit pupil plane of the fixed-focus lens to the image plane, and HI is the maximum image plane of the fixed-focus lens.

[0070] In this embodiment, setting the fixed-focus lens to satisfy the above conditions aims to adjust the target surface and control the total optical length at the same time. When EXPP / HI is greater than -1.181, the exit pupil plane gradually approaches the image plane, and the angle of the marginal chief rays incident on the image plane increases, resulting in the imaging element unit being unable to fully receive the optical signal; while if EXPP / HI is greater than -1.051, increasing the total length will be required to achieve the same effect.

[0071] In a specific embodiment, optionally, the fixed-focus lens satisfies the following condition: -0.229 ≤ DIS / HI ≤ 0.153; where HI is the maximum image plane of the fixed-focus lens, and DIS is the optical distortion of the fixed-focus lens.

[0072] In this embodiment, setting the fixed-focus lens to meet the above conditions can control the distortion of the entire optical system, making the distortion very small and not affecting the imaging effect, thus ensuring the imaging quality.

[0073] In a specific embodiment, the fixed-focus lens may further include a low-pass filter 600. The low-pass filter 600 is disposed on the image plane side of the fourteenth lens 414. The low-pass filter 600 can filter out unnecessary stray light, thereby improving the image quality of the fixed-focus lens. For example, by filtering out infrared light during the day through the low-pass filter 600, the imaging quality of the fixed-focus lens can be improved. At the same time, the low-pass filter 600 can also protect the photosensitive chip.

[0074] The internal focusing full-frame mirrorless fixed-focus lens provided by the embodiments of the present invention adopts an all-glass structure. By matching the lens materials and reasonably distributing the optical power of each element, a fixed-focus lens design with a focal length of 24 mm, an imaging target plane of 43.2 mm, and an F number of 2.0 is achieved. When the aperture is fully open, the MTF values of all fields reach above 0.6 at a spatial frequency of 30 lp / mm, while achieving |distortion| ≤ 1%. And the lateral chromatic aberration is corrected.

[0075] Based on the same above concept, the present invention provides three different specific embodiments. The optical power relationship and the design ranges of relevant physical optical parameters are shown in Table 1:

[0076]

[0077]

[0078] In the first embodiment of the present invention, referring to Figure 1 it can be known the structural composition of each element in the entire optical system, as well as the shape and position of each element. This is crucial for the system. It can be seen from the figure that the optical system is composed of 14 optical lenses. The overall layout of the system is that there are 5 lens elements in front of the aperture and 9 lens elements behind the aperture; among them, the fourth lens 104 and the fifth lens 105 form a group of cemented lenses, the seventh lens 207 and the eighth lens 208 form a group of cemented lenses, and the thirteenth lens 413 and the fourteenth lens 414 form a group of cemented lenses.

[0079] As Figure 1 shown, the parameter design values of each lens in the fixed-focus lens of the first embodiment are shown in Table 2:

[0080] Table 2 Design values of each lens in the fixed-focus lens of the first embodiment

[0081]

[0082]

[0083]

[0084] The surface numbers in Table 2 are numbered according to the surface order of each lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane side, and a negative value indicates that the surface bends towards the object plane side; where "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, a space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light. The semi-aperture represents half of the aperture size of the current surface.

[0085] The aspherical conic coefficient can be defined by the following aspherical formula, but is not limited to the following representation:

[0086]

[0087] where z is the axial sagittal height in the Z direction of the aspherical surface; r is the height of the aspherical surface; c is the curvature of the fitted spherical surface, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; A - G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0088] The coefficient values of each aspherical surface in the first embodiment above are shown in Table 3:

[0089] Table 3 Parameters of each aspherical surface

[0090]

[0091]

[0092] Among them, 1.274669E-04 means that the coefficient A of the surface number S19 is 1.274669 * 10 -4 , and so on.

[0093] The technical indicators achieved by the fixed-focus lens shown in the first embodiment above are shown in Table 4:

[0094] Table 4 Parameter indicators of the fixed-focus lens:

[0095] Image plane size (mm) Φ43.2 Focal length (mm) 24.285 Overall optical length (mm) 105.1 F / # 2.0 Field of view angle (°) 83.21

[0096] Figure 2 YesFigure 1 The MTF curve graph of the fixed-focus lens shown, where the MTF graph is one of the most commonly used and authoritative evaluation methods in modern optical design. The abscissa is the spatial frequency at which the line pairs in the object space are imaged on the image plane through the optical system, and the ordinate is the modulus value of the optical transfer function. Different curves represent the change trends of the optical transfer functions of the images in the meridional and sagittal directions of different fields of view as the spatial frequency increases. The most ideal curve is a straight line that coincides with the diffraction limit of the system, indicating that the geometric aberrations of the light rays at all positions are less than the wavefront aberration generated by the physical limitations of the system itself and can be ignored. From Figure 2 it can be seen that at 30 lp / mm for the imaging of each field of view of this system, its optical transfer function is relatively high, and the trend change is gentle and smooth. This indicates that this optical system can meet the imaging requirements of high resolution and uniform image quality.

[0097] Figure 3 is Figure 1 The field curvature and distortion curve graph of the fixed-focus lens shown. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; where T represents the meridional and S represents the sagittal; from Figure 3 it can be seen that the field curvature of the lens provided in this embodiment is effectively controlled, that is, when imaging, the image quality difference between the center and the periphery is small; in the coordinate system on the right side, the horizontal coordinate represents the magnitude of the distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit; from Figure 3 it can be seen that the distortion of the lens provided in this embodiment is well corrected and the imaging distortion is small.

[0098] Figure 4 is Figure 1 The lateral chromatic aberration curve graph of the fixed-focus lens shown, where the abscissa is the lateral distance of the light rays of other wavelengths from the principal wavelength light ray on the image plane, and the ordinate is the field of view. The curve describes the lateral chromatic aberration of the light rays of different fields of view and different wavelengths on the image plane. The most ideal curve is that the light rays of all wavelengths are within the radius of the Airy disk, indicating that the lateral chromatic aberration of the light rays at all fields of view is less than the wavefront aberration generated by the physical limitations of the system itself. From Figure 4 it can be seen that the lateral chromatic aberration of the lens provided in this embodiment is effectively controlled, that is, when imaging, it is not easy to have situations such as smear and purple fringing in places with large contrast.

[0099] Figure 5 This is a schematic structural diagram of an internal focusing full-frame mirrorless fixed-focus lens provided in the second embodiment of the present invention at an infinite object distance. In the second embodiment of the present invention, refer to Figure 5It is possible to know the structural composition of each component in the entire optical system, as well as the shape and position of each component, which is crucial for the system. As can be seen from the figure, the optical system consists of 14 optical lenses. The overall layout of the system is such that there are 5 lens elements in front of the aperture and 9 lens elements behind the aperture. Among them, the fourth lens 104 and the fifth lens 105 form a set of cemented lenses, the seventh lens 207 and the eighth lens 208 form a set of cemented lenses, and the thirteenth lens 413 and the fourteenth lens 414 form a set of cemented lenses.

[0100] As Figure 5 shown, the parameter design values of each lens in the fixed-focus lens of Embodiment 2 are shown in Table 5:

[0101] Table 5 A set of design values of each lens in the fixed-focus lens of Embodiment 2

[0102]

[0103]

[0104]

[0105] The surface numbers in Table 5 are numbered according to the surface order of each lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value indicates that the surface bends towards the image plane side, and a negative value indicates that the surface bends towards the object plane side. Among them, "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, a space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristics of the material between the current surface and the next surface to light. The semi-aperture represents half of the aperture size of the current surface.

[0106] The aspherical conic coefficient can be defined by the following aspherical formula, but is not limited to the following representation:

[0107]

[0108] Among them, z is the axial sagittal height of the aspherical surface in the Z direction; r is the height of the aspherical surface; c is the curvature of the fitted spherical surface, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; A - G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0109] The coefficient values of each aspherical surface in Embodiment 2 above are shown in Table 6:

[0110] Table 6 Parameters of each aspherical surface

[0111]

[0112] Among them, 1.275477E-04 indicates that the coefficient A with the surface serial number S19 is 1.275477 * 10 -4 , and so on.

[0113] The technical indicators achieved by the fixed-focus lens shown in the above Embodiment 2 are shown in Table 7:

[0114] Table 7 Fixed-focus lens parameter indicators:

[0115] Image plane size (mm) Φ43.2 Focal length (mm) 24.930 Overall optical length (mm) 106.9 F / # 2.0 Field of view angle (°) 81.08

[0116] Figure 6 is Figure 5 the MTF curve graph of the resolution of the shown fixed-focus lens. Among them, the MTF graph is one of the most commonly used and authoritative evaluation methods in modern optical design. The abscissa is the spatial frequency at which the line pairs in the object space are imaged on the image plane through the optical system, and the ordinate is the modulus value of the optical transfer function. Different curves represent the change trends of the optical transfer functions of the images in the meridional and sagittal directions of different fields of view as the spatial frequency increases. The most ideal curve is a straight line that coincides with the system diffraction limit, indicating that the geometric aberrations of the light rays at all positions are less than the wavefront aberration generated by the physical limitations of the system itself and can be ignored. From Figure 6 it can be seen that at 30 lp / mm for the imaging of each field of view of this system, its optical transfer function is relatively high, and the trend change is gentle and smooth. This indicates that this optical system can meet the imaging requirements of high resolution and uniform image quality.

[0117] Figure 7 is Figure 5 the field curvature and distortion curve graph of the shown fixed-focus lens. In the left coordinate system in the figure, the horizontal coordinate represents the magnitude of the field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without a unit; where T represents meridional and S represents sagittal; from Figure 7 it can be seen that the field curvature of the lens provided in this embodiment is effectively controlled, that is, during imaging, the image quality difference between the center and the periphery is small; in the right coordinate system, the horizontal coordinate represents the magnitude of the distortion, with the unit of %; the vertical coordinate represents the normalized image height, without a unit; from Figure 7 it can be seen that the distortion of the lens provided in this embodiment is well corrected and the imaging distortion is small.

[0118] Figure 8 is Figure 5 the lateral chromatic aberration curve graph of the shown fixed-focus lens. Among them, the abscissa is the lateral distance of the light rays of other wavelengths from the principal wavelength light ray on the image plane, and the ordinate is the field of view. The curve describes the lateral chromatic aberration of the light rays of different fields of view and different wavelengths on the image plane. The most ideal curve is that the light rays of all wavelengths are within the radius of the Airy disk, indicating that the lateral chromatic aberration of the light rays at all fields of view is less than the wavefront aberration generated by the physical limitations of the system itself. From Figure 8It can be seen that the lateral chromatic aberration of the lens provided in this embodiment is effectively controlled, that is, during imaging, it is not easy to have phenomena such as smear and purple fringing in areas with large contrast.

[0119] Figure 9 FIG. 4 is a schematic structural diagram of an internal focusing full-frame mirrorless prime lens provided in Embodiment 3 of the present invention at an infinite object distance. In Embodiment 3 of the present invention, referring to Figure 9 it can be known the structural composition of each element in the entire optical system, as well as the shape and position of each element, which is crucial for the system. It can be seen from the figure that the optical system is composed of 14 optical lenses. The overall layout of the system is that there are 5 lens elements in front of the aperture stop and 9 lens elements behind the aperture stop; among them, the fourth lens 104 and the fifth lens 105 form a group of cemented lenses, the seventh lens 207 and the eighth lens 208 form a group of cemented lenses, and the thirteenth lens 413 and the fourteenth lens 414 form a group of cemented lenses.

[0120] As Figure 9 shown, the parameter design values of each lens in the prime lens of Embodiment 3 are shown in Table 8:

[0121] Table 8 A set of design values of each lens in the prime lens of Embodiment 3

[0122]

[0123]

[0124] The surface numbers in Table 8 are numbered according to the surface order of each lens; the radius of curvature represents the degree of curvature of the lens surface. A positive value represents that the surface bends towards the image plane side, and a negative value represents that the surface bends towards the object plane side; among them, "INF" indicates that the surface is a plane and the radius of curvature is infinite; the thickness represents the central axial distance from the current surface to the next surface, the refractive index represents the ability of the material between the current surface and the next surface to deflect light, a space represents that the current position is air and the refractive index is 1; the Abbe number represents the dispersion characteristic of the material between the current surface and the next surface to light. The semi-aperture represents half of the aperture size of the current surface.

[0125] The aspherical conic coefficient can be defined by the following aspherical formula, but is not limited to the following representation:

[0126]

[0127] where z is the axial sagittal height of the aspherical surface in the Z direction; r is the height of the aspherical surface; c is the curvature of the fitted spherical surface, numerically the reciprocal of the radius of curvature; k is the fitted conic coefficient; A - G are the coefficients of the 4th, 6th, 8th, 10th, 12th, 14th, and 16th order terms of the aspherical polynomial.

[0128] The coefficient values of each aspherical surface in the above Embodiment 3 are shown in Table 9 as follows:

[0129] Table 9 Aspherical surface parameters

[0130]

[0131] Among them, 1.276517E-04 indicates that the coefficient A of the surface serial number S19 is 1.276517×10 -4 , and so on.

[0132] The technical indicators achieved by the fixed-focus lens shown in the above Embodiment 3 are shown in Table 10 as follows:

[0133] Table 10 Parameter indicators of the fixed-focus lens:

[0134] Image plane size (mm) Φ43.2 Focal length (mm) 21.5 Overall optical length (mm) 99.91 F / # 2.0 Field of view angle (°) 92.84

[0135] Figure 10 is Figure 9 The MTF curve graph of the resolving power of the shown fixed-focus lens. Among them, the MTF graph is one of the most commonly used and authoritative evaluation methods in modern optical design. The abscissa is the spatial frequency at which the line pairs in the object space are imaged on the image plane through the optical system, and the ordinate is the modulus value of the optical transfer function. Different curves represent the change trends of the optical transfer functions of the images in the meridional and sagittal directions of different fields as the spatial frequency increases. The most ideal curve is a straight line that coincides with the diffraction limit of the system, indicating that the geometric aberrations of the light rays at all positions are less than the wavefront aberration generated by the physical limitations of the system itself and can be ignored. From Figure 10 , it can be seen that at 30 lp / mm for the imaging of each field of this system, its optical transfer function is relatively high, and the trend change is gentle and smooth. This indicates that this optical system can achieve the imaging requirements of high resolution and uniform image quality.

[0136] Figure 11 is Figure 9 The field curvature and distortion curve graph of the shown fixed-focus lens. In the coordinate system on the left side of the figure, the horizontal coordinate represents the magnitude of the field curvature, with the unit of mm; the vertical coordinate represents the normalized image height, without unit; where T represents meridional and S represents sagittal; from Figure 11 , it can be seen that the field curvature of the lens provided in this embodiment is effectively controlled, that is, when imaging, the image quality difference between the center and the periphery is small; in the coordinate system on the right side, the horizontal coordinate represents the magnitude of the distortion, with the unit of %; the vertical coordinate represents the normalized image height, without unit; from Figure 11 , it can be seen that the distortion of the lens provided in this embodiment is well corrected and the imaging distortion is small.

[0137] Figure 12 is Figure 9The vertical chromatic aberration curve diagram of the shown fixed-focus lens, where the abscissa is the vertical distance of other wavelength light rays from the principal wavelength light ray on the image plane, and the ordinate is the field of view. The curve describes the vertical chromatic aberration of light rays with different fields of view and different wavelengths on the image plane. The most ideal curve is that all wavelength light rays are within the radius of the Airy disk, indicating that the vertical chromatic aberration of light rays on all fields of view is less than the wave aberration generated by the physical limitations of the system itself. From Figure 12 It can be seen that the vertical chromatic aberration of the lens provided in this embodiment is effectively controlled, that is, when imaging, it is not easy to have situations such as smear and purple fringing in places with large contrast.

[0138] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described here, and various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. An internal focusing full-frame micro single fixed-focus lens, characterized in that: The optical lens comprises a first lens with negative power, a second lens with negative power, a third lens with negative power, a fourth lens with negative power, a fifth lens with positive power, a stop, a sixth lens with positive power, a seventh lens with negative power, an eighth lens with positive power, a ninth lens with positive power, a tenth lens with positive power, an eleventh lens with negative power, a twelfth lens with negative power, a thirteenth lens with positive power and a fourteenth lens with negative power, which are arranged in sequence from the object side to the image side along the optical axis; The first lens, the second lens, the third lens, the fourth lens and the fifth lens constitute a first lens group having a negative total optical power; The sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens and the eleventh lens constitute a second lens group having a positive total optical power; The twelfth lens constitutes a third lens group having a negative total optical power; The thirteenth lens and the fourteenth lens constitute a fourth lens group having positive total refractive power.

2. The fixed-focus lens according to claim 1, characterized in that: Each lens group meets the following conditions: 0.462≤F1 / F3≤0.615; -0.452≤F2 / F3≤-0.407; -24.136≤F4 / F3≤-1.163; Among them, F1 is the total optical power of the first lens group, F2 is the total optical power of the second lens group, F3 is the total optical power of the third lens group, and F4 is the total optical power of the fourth lens group.

3. The fixed-focus lens according to claim 1, characterized in that: The first lens to the fourteenth lens are all glass lenses.

4. The fixed-focus lens according to claim 1, characterized in that: The first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, the eighth lens, the ninth lens, the tenth lens, the thirteenth lens, and the fourteenth lens are spherical lenses; The eleventh lens and the twelfth lens are aspherical lenses.

5. The fixed-focus lens according to claim 1, wherein: The first lens satisfies the following condition: 3.085≤(R1+R2) / (R1-R2)≤4.046; Wherein, R1 is the curvature radius of a surface of the first lens close to the object side, and R2 is the curvature radius of a surface of the first lens close to the image side.

6. The fixed-focus lens according to claim 1, wherein: The first lens satisfies the following conditions: 0.319≤U1 / F1≤0.445; Wherein, U1 is the optical power of the first lens, and F1 is the total optical power of the first lens group.

7. The fixed-focus lens according to claim 1, wherein: The first lens and the second lens meet the following conditions: Vd1≥95; Vd2≥95; Wherein, Vd1 is the Abbe number of the first lens, and Vd2 is the Abbe number of the second lens.

8. The fixed-focus lens according to claim 1, wherein: The third lens group satisfies the following conditions: -1.214≤SI / F3≤-0.658; Wherein, F3 is the total optical power of the third lens group, and SI is the distance from the aperture to the image plane.

9. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens meets the following conditions: -1.181≤EXPP / HI≤-1.051; Wherein, EXPP is the distance from the exit pupil plane to the image plane of the fixed-focus lens, and HI is the maximum image plane of the fixed-focus lens.

10. The fixed-focus lens according to claim 1, wherein: The fixed-focus lens meets the following conditions: -0.229≤DIS / HI≤0.153; Wherein, HI is the maximum image plane of the fixed-focus lens, and DIS is the optical distortion of the fixed-focus lens.

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