55 results about "Prime lens" patented technology

The utility model discloses a prime lens comprising a front lens group, a diaphragm and a rear lens group which are arranged from an object plane to an image plane along an optical axis. The front lens group comprises a first lens, a second lens and a third lens which are sequentially arranged from the object plane to the image plane, the focal power of the first lens is negative, the focal power of the second lens is negative, and the focal power of the third lens is positive; the focal power of the rear lens group is positive, and the rear lens group comprises a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from the object plane to the image plane, the focal power of the fourth lens is positive, the focal power of the fifth lens is negative, the focal power of the sixth lens is positive, the focal power of the seventh lens is negative, and the focal power of the eighth lens is positive; the focal power of the front lens group is phi front, the focal power of the rear lens group is phi rear, and the focal power of the prime lens is phi; wherein-0.085 < = phi front / phi < = 0.25, and 0.35 < = phi rear / phi < = 0.48. Through the lens group and the focal power distribution of each lens, the design of a large-aperture and large-target-surface prime lens can be realized.

The prime lens comprises a front lens group, a diaphragm and a rear lens group which are sequentially arranged from an object side to an image side, the front lens group is sequentially provided with a first lens, a second lens and a third lens with negative focal power, negative focal power and positive focal power from the object side to the image side; the rear lens group is sequentially provided with a fourth lens, a fifth lens, a sixth lens and a seventh lens with positive focal power, negative focal power, positive focal power and positive focal power from the object side to the image side; wherein the fourth lens and the fifth lens are glued to form a doublet lens. The prime lens is composed of seven lens elements, the number of the lenses is reasonable, the structure is simple and compact, the focal power and the position of each lens element are reasonable, the environment adaptability is high, and the resolving power is high; due to the design of the large field angle and the large image height, the lens system has higher competitiveness in the market. The aperture number FNO of the prime lens is 2.50, the field angle is 138 degrees, the imaging height can be matched with a 1 / 1.8 inch chip, the total optical length is not larger than 24.0 mm, the optical distortion absolute value is smaller than 40%, and the requirement for ultra-high-definition imaging is met.

The embodiment of the utility model discloses an ultra-wide-angle and ultra-short-focus full-width camera lens, which comprises sixteen lenses which are sequentially arranged from an object space to an image space along an optical axis, and each lens has corresponding focal power; besides, a diaphragm is arranged between the eighth lens and the ninth lens to divide the sixteen lenses into two lens groups, namely a first lens group with negative total focal power and a second lens group with positive total focal power. According to the full-frame prime lens provided by the embodiment of the utility model, by using the optical structure of the 14 glass spherical lenses and the 2 glass aspherical lenses, when the full field angle is greater than or equal to 132 degrees, the distortion is small, and the purple edge phenomenon is improved. Besides, by adding the aspherical lens, the image quality of an edge field of view is also obviously improved under an ultra-short focal length, clear imaging can be realized, and the shooting feeling of almost zero distortion is achieved.

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens is a negative-focal-power lens, the second lens is a negative-focal-power lens, the third lens is a positive-focal-power lens, the fourth lens is a positive-focal-power lens or a negative-focal-power lens, and the fifth lens is a positive-focal-power lens; the surface of the lens adjacent to the object surface is an object-side surface, and the surface of the lens adjacent to the image surface is an image-side surface; the curvature radius of the object side surface of the fourth lens is R41, the curvature radius of the image side surface of the fourth lens is R42, the focal length of the fourth lens is F4, the curvature radius of the object side surface of the fifth lens is R51, the curvature radius of the image side surface of the fifth lens is R52, and the focal length of the fifth lens is F5. According to the technical scheme provided by the embodiment of the invention, the design of the vehicle-mounted lens which is high in imaging quality, compact in structure, large in aperture and large in field angle can be realized.

The utility model discloses a prime lens. The prime lens sequentially comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens from an object side to an image side along an optical axis, the first lens has negative focal power, the object side surface is a convex surface, and the image side surface is a concave surface; the second lens has positive focal power, the object side surface of the second lens is a concave surface, and the image side surface is a convex surface; the third lens has positive focal power, the object side surface of the third lens is a concave surface, and the image side surface is a convex surface; the fourth lens has negative focal power; the fifth lens has positive focal power; the sixth lens has negative focal power, the object side surface of the sixth lens is a concave surface, and the image side surface is a convex surface; the seventh lens has positive focal power; the eighth lens has negative focal power.

The invention discloses a photometric three-dimensional imaging method and a high-speed photometric three-dimensional imaging device, and relates to the technical field of industrial detection.Partition light sources which are evenly distributed are arranged in the vertical direction of a sample to be detected, and the partition light sources are correspondingly provided with area-array cameras and prime lenses; the partitioned light source comprises four light sources which are independently controlled, each light source is turned on / off under a set program during image acquisition, only one light source is turned on / off each time, and the other light sources are in opposite states, namely turned off / on; the method comprises the following steps: acquiring a sample image in the on / off state of each light source, combining and registering two images acquired in the on / off state of two light sources, then calculating a uniform illumination image and two primary difference images, and further calculating a pseudo depth image and a contour image. On the basis of five images obtained through processing, high-speed detection of a single sample can be achieved within 50 ms, and the detection requirement in an actual industrial scene can be better met.

The utility model discloses a prime lens and monitoring equipment. The prime lens comprises a convex-concave first lens with positive focal power, a field diaphragm, a second lens with negative focal power, a third lens with positive focal power, a convex-convex fourth lens with positive focal power, a concave-concave fifth lens with negative focal power and a sixth lens with positive focal power which are sequentially arranged from an object space to an image space along an optical axis, the vignetting diaphragm comprises a convex seventh lens with positive focal power and a concave eighth lens with negative focal power; the image side surface of the second lens is a concave surface, the object side surface of the third lens is a convex surface, the image side surface of the sixth lens is a convex surface, the second lens and the third lens are cemented into a first cemented lens, and the fourth lens and the fifth lens are cemented into a second cemented lens. And high resolution performance is achieved in visible light and near-infrared bands.

The invention provides a wide-angle prime lens, and relates to the technical field of optical lenses. The wide-angle prime lens provided by the embodiment of the invention comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, an eighth lens, a ninth lens and a tenth lens which are sequentially arranged from an object space to an image space along an optical axis, the first lens and the second lens have negative focal power; the third lens and the fourth lens have positive focal power; the wide-angle prime lens further comprises a diaphragm, and the diaphragm is located between the third lens and the fourth lens. The embodiment of the invention provides a wide-angle prime lens, so as to realize the wide-angle prime lens with small aperture and high image quality.

The prime lens comprises a first lens with negative focal power, a second lens with positive focal power, a third lens with negative focal power and a fourth lens with positive focal power which are arranged from an object plane to an image plane along an optical axis, the object-side surface of the first lens is a convex surface, and the image-side surface is a concave surface. The object side surface of the second lens is a convex surface, and the image side surface is a concave surface; the object side surface of the third lens is a concave surface, and the image side surface is a convex surface; the fourth lens element has a convex object-side surface and a convex image-side surface. According to the technical scheme, the arrangement of the four lenses ensures that the number of the lenses in the prime lens is small, and the realization of small size and low cost is facilitated; and an M12 interface can be adopted, so that the cost can be further reduced. Furthermore, the focal power of the first lens and the third lens is negative, the focal power of the second lens and the fourth lens is positive, and the good imaging effect of the optical system can be ensured by reasonably distributing the focal power of each lens in the optical system.

The invention provides a prime lens. The prime lens comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with focal power, a fourth lens with positive focal power, a fifth lens with focal power, a sixth lens with focal power and a seventh lens with focal power which are sequentially arranged from the object space to the image space along the optical axis. The first lens has focal power, the second lens has focal power, the eighth lens has focal power, the ninth lens has positive focal power, the prime lens comprises five glass spherical lenses and four plastic aspheric lenses, the second lens, the third lens or the seventh lens, and the eighth lens and the ninth lens are plastic aspheric lenses. The aperture of the prime lens provided by the invention is 0.864, the maximum field angle is 140.24 degrees, the imaging target surface phi is greater than or equal to 9.2 mm, the prime lens can be matched with a 1 / 1.8 inch chip, and the requirements of large aperture and large field angle are met.

The invention discloses an optical system of a large-aperture full-frame prime lens, which belongs to the technical field of optical lens manufacturing, and comprises a first objective lens group G1, a second objective lens group G2 and a third objective lens group G3 which are sequentially arranged from an object side to an image side along an optical axis direction, and a radial diaphragm is positioned in the first objective lens group; in the focusing process, the second objective lens group G2 moves towards the image side along the optical axis, and the first objective lens group G1, the aperture diaphragm and the third objective lens group G3 remain unchanged relative to the position of the image plane. The optical system satisfies the following conditional expressions: 0.87 < = FG1 / F < = 1.25; 0.62 < = FG2 / F < = 0.98; 0.7 < = FG3 / F < = 1.2. The first objective lens group comprises four single lenses with positive focal power, a doublet lens with negative focal power, a single lens with negative focal power and an aperture diaphragm; and the third objective lens group comprises a single lens with positive focal power, a quadruple bonding lens and two lenses with negative focal power, wherein one lens is an aspheric lens. According to the invention, good imaging quality can be realized.

The utility model discloses a prime lens and machine vision equipment. The prime lens comprises a first lens with negative focal power, a second lens with positive focal power, a third lens with positive focal power, a fourth lens with negative focal power, a fifth lens with focal power, a sixth lens with focal power and a seventh lens with positive focal power which are sequentially arranged from the object space to the image space. An eighth lens with positive focal power, a ninth lens with focal power and a tenth lens with focal power; wherein the fifth lens and the sixth lens are glued to form a first glued lens with negative focal power, and the ninth lens and the tenth lens are glued to form a second glued lens with positive focal power. The focal length of the prime lens is 16mm, the field angle is 39.4 degrees, the TV distortion of the lens is less than 0.04%, the optical distortion is less than 0.4%, and the lens can work stably at 10-50 DEG C.

The invention discloses a prime lens and monitoring equipment. The prime lens comprises a convex-concave first lens with positive focal power, a field diaphragm, a second lens with negative focal power, a third lens with positive focal power, a convex-convex fourth lens with positive focal power, a concave-concave fifth lens with negative focal power and a sixth lens with positive focal power which are sequentially arranged from an object space to an image space along an optical axis, the vignetting diaphragm comprises a convex seventh lens with positive focal power and a concave eighth lens with negative focal power; the image side surface of the second lens is a concave surface, the object side surface of the third lens is a convex surface, the image side surface of the sixth lens is a convex surface, the second lens and the third lens are cemented into a first cemented lens, and the fourth lens and the fifth lens are cemented into a second cemented lens. And high resolution performance is achieved in visible light and near-infrared bands.

The utility model provides a prime lens, and relates to the technical field of optical lenses. The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object space to an image space along an optical axis; the first lens is a glass spherical lens with negative focal power, the second lens is a plastic aspheric lens with negative focal power, the third lens is a plastic aspheric lens with positive focal power, the fourth lens is a glass spherical lens with negative focal power, and the fifth lens is a plastic aspheric lens with positive focal power. The fifth lens is a glass spherical lens with positive focal power, the sixth lens is a plastic aspheric lens with positive focal power, the seventh lens is a plastic aspheric lens with negative focal power, and the eighth lens is a plastic aspheric lens with positive focal power. According to the embodiment of the utility model, the prime lens which has the advantages of wide angle, compact structure, high image quality, large target surface and excellent comprehensive performance is realized.

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.

The invention discloses a relay optical system and a lens device.The relay optical system is used for being detachably installed on a prime lens and is provided with an object side and an image side which are correspondingly arranged in the optical axis direction. The relay optical system comprises a first lens, a second lens, a third lens, a fourth lens and an image plane which are sequentially arranged from an object side to an image side, and the relay optical system meets the following conditions:-70mlt; f1lt; the thickness is-10 mm, and the thickness is-150 mmlt; f2lt; f2lt; the thickness is-90 mm, and the thickness is 100 mmlt; f3lt; f3t; the thickness is 150 mm, and the thickness is 30 mlt; f4lt; f4t; the focal length of the first lens is f1, the focal length of the second lens is f2, the focal length of the third lens is f3, and the focal length of the fourth lens is f4. Through the arrangement, the shooting complexity and time cost are effectively reduced, and meanwhile, the overall investment cost is also reduced. And the size of the relay optical system is reduced, and the weight of the relay optical system is reduced, so that the relay optical system is convenient to carry.

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object side to an image side along an optical axis, the first lens has positive focal power, the second lens has positive focal power, the third lens has focal power, and the fourth lens has focal power. The fourth lens has focal power, the fifth lens has negative focal power, the sixth lens has positive focal power, the seventh lens has focal power, and the eighth lens has negative focal power. According to the prime lens provided by the embodiment of the utility model, the eight lenses are adopted, the focal power of each lens is reasonably distributed, and the surface types of part of the lenses are further set, so that a telephoto lens which has a longer shot distance under a large target surface, stable high and low temperature performance, a large aperture, small distortion and clear imaging is realized; and the use requirements under more conditions can be met.

The utility model discloses a prime lens which comprises three lens groups. The first lens group with the positive focal power comprises a meniscus positive lens, a pair of doublet lenses with a cemented surface approximate to a plane and another meniscus positive lens, and the distance between the central axes of the last two lenses is less than 1.0 mm. The movable second lens group is only provided with one negative lens, and the absolute value of the focal length is 0.7 time of the total focal length of the prime lens. And the third lens group with the positive focal power comprises a pair of doublet lenses, a biconvex spherical positive lens, a biconcave spherical negative lens, another pair of doublet lenses and a meniscus negative lens. The prime lens can be used for a full-frame camera, does not contain an aspheric surface, and is low in cost.

The utility model relates to a foldable mobile phone middle frame torque track detection device comprising a machine body comprising a machine body and a machine cover; the two track capturing assemblies are mounted at the top of the machine body; the track capturing assembly comprises an industrial camera and a prime lens; the prime lens comprises a main body and a butt joint part; the two folding assemblies are mounted in the machine body; the folding assembly comprises a hollow rotating platform, a static torque sensor, a fixed clamping jaw and a movable clamping jaw. The folding mobile phone middle frame torque track detection equipment is simple in structure and convenient to use, the prime lens and the industrial camera are installed at the top of the hood, the axis of the static torque sensor coincides with the axis of the prime lens, tiny deformation and movement in the middle frame folding process can be captured, analysis completeness can be improved, and the detection efficiency is improved. Potential quality problems can be found in time, and it is ensured that the produced folding mobile phone can meet the expected requirements for durability and stability.

The invention discloses a prime lens. The prime lens comprises a first lens with negative focal power, a second lens with negative focal power, a third lens with positive focal power, a fourth lens with positive focal power, a fifth lens with positive focal power, a sixth lens with focal power and a seventh lens with positive focal power which are sequentially arranged from an object side to an image side along an optical axis, an eighth lens with negative focal power, a ninth lens with positive focal power and a tenth lens with focal power; the first lens, the fourth lens, the eighth lens and the ninth lens are glass spherical lenses, the third lens and the seventh lens are glass aspheric lenses, and the second lens, the fifth lens, the sixth lens and the tenth lens are plastic aspheric lenses. According to the scheme, on the premise that it is ensured that the prime lens has the small size and the large field angle, the prime lens can be suitable for high and low temperature environments, and the prime lens has more application scenes.

The invention relates to the field of optics, in particular to a prime lens and an imaging device.The prime lens sequentially comprises a first lens with negative focal power, a second lens with negative focal power, a third lens, a fourth lens, a fifth lens with positive focal power, a sixth lens with positive focal power and a seventh lens with negative focal power from the object plane side to the image plane side, the system is composed of a first lens with positive focal power, an eighth lens with positive focal power, a ninth lens with negative focal power, a tenth lens with positive focal power and an eleventh lens with negative focal power. The prime lens satisfies the following conditional expressions: fno < 0.9; tTL / f is less than 12; wherein fno is the number of apertures of the prime lens, TTL is the total optical length of the prime lens, and f is the focal length of the prime lens. According to the prime lens, the aperture of the prime lens is greatly increased, the prime lens can be better used in a dark scene, and the size of the prime lens is reduced and miniaturization of the prime lens is realized due to the arrangement of the multiple groups of bonding lenses and the limitation of the total optical length.

The embodiment of the invention provides a camera calibration method and device, and the method comprises the steps: obtaining the theoretical parameters of a target camera, the target camera is a monocular camera or a binocular camera, the lens of the monocular camera is a zoom lens or a prime lens, and the binocular camera comprises a zoom lens and a prime lens; and calibrating the target camera according to the theoretical parameters. Through the method and the device, the problem of relatively high resource utilization rate caused by non-uniform calibration environments of a prime lens and a zoom lens in related technologies is solved, and the effect of improving the lens calibration efficiency is further achieved.

The invention discloses an optical system of a large-aperture half-frame prime lens, the optical system comprises a first objective lens group, an aperture diaphragm, a second objective lens group and a third objective lens group, the first objective lens group, the second objective lens group and the third objective lens group are sequentially arranged from an object side to an image side along an optical axis direction, the aperture diaphragm is located in the first objective lens group, and the aperture diaphragm is located in the third objective lens group. In the focusing process, the second objective lens group moves towards the image side along the optical axis, and the first objective lens group, the aperture diaphragm and the third objective lens group remain unchanged relative to the image plane position. According to the optical system, the positive focal power and the negative focal power of all the lens groups and the proportion of the combined focal length of all the lens groups to the combined focal length of the whole lens are set; the purposes of optimizing refraction and convergence of light, balancing aberration and improving imaging quality are achieved, and the lens is further made to achieve high image quality.

The utility model relates to a portable and multipurpose monocular digital image full-field deformation measuring device which comprises a shell, lighting sources, a digital image measuring system, a computer and an integrated board, a plurality of lighting sources are arranged on the front side of the shell, and the digital image measuring system and the integrated board are respectively arranged inside the shell. The integrated board is electrically connected with the illumination light source and the digital image measurement system; the digital image measuring system comprises a stepping motor, a sliding table module, an adapter plate, a camera and a prime lens, the sliding table module is arranged at the bottom in the shell, the stepping motor is arranged on one side of the sliding table module and drives a sliding table on the sliding table module to reciprocate, the adapter plate is arranged at the top of the sliding table, the camera is arranged at the top of the adapter plate, and the prime lens is arranged on the front side of the camera. A strip-shaped through hole is formed in the front side of the shell, and the prime lens penetrates out of the through hole and moves in the through hole. According to the utility model, camera movement control, light adjustment, signal transmission and the like are integrated, the structure is compact, the versatility is strong, and the carrying is convenient.

The prime lens comprises a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and an eighth lens which are sequentially arranged from an object plane to an image plane along an optical axis, the first lens is a negative-focal-power biconcave lens, the second lens is a negative-focal-power concave-convex lens, the third lens is a positive-focal-power convex-concave lens, the fourth lens is a positive-focal-power lens, the image side face of the fourth lens is a convex face, the fifth lens is a positive-focal-power biconvex lens, the sixth lens is a negative-focal-power biconcave lens, and the seventh lens is a positive-focal-power biconvex lens. And the eighth lens is a convex-concave lens with negative focal power. According to the technical scheme, the prime lens comprises eight lenses, and the focal power and the surface type of each lens are reasonably distributed, so that the imaging quality of the optical system is improved, the prime lens is ensured to have a good imaging effect, the relative illumination between an edge image and a center image can be improved, and the imaging quality of the optical system is improved. And the imaging requirement of the security lens is met.

The utility model discloses a machine vision prime lens with an improved structure and a focal length of 12mm, which comprises a first lens, a second lens arranged on the right side of the first lens, a first diaphragm arranged on the right side of the second lens, a third lens arranged on the right side of the first diaphragm, a fourth lens arranged on the right side of the third lens, and a fifth lens arranged on the right side of the fourth lens. The fourth lens and the fifth lens are bonded through optical glue to form a gluing piece, the focal length of the first lens is fg1, the focal length of the gluing piece is fu4, the focal length of the lens is f, and the optical system meets the relational expression of 0.4 lt; fg1 / flt; 1, 1.3, 0.3 lt; fu4 / flt; and 0.8. The utility model has the advantages of novel design, simple structure, simple and convenient assembly, low cost, good optical performance, clear imaging and high resolution, and realizes the change of the object distance from 0.1 m to infinity.

The utility model belongs to the technical field of lenses, and discloses a detachable prime lens and a mobile phone. The detachable prime lens comprises a front group, a rear group, a transmission member, a rotation driving assembly and a linear driving assembly. Wherein the front group is fixedly connected with the transmission part, the transmission part can rotate around the axis of the transmission part and ascend and descend along the axis of the transmission part, the rotation driving assembly is used for driving the transmission part to rotate, and the linear driving assembly is used for driving the transmission part to ascend and descend. The front group and the rear group are arranged to be two split parts, so that when the rotary driving assembly can drive the transmission part to rotate and the linear driving assembly drives the transmission part to ascend and descend, the transmission part can drive the front group to rotate and ascend and descend. According to the detachable prime lens, the front group and the rear group are coaxial to meet shooting requirements when the detachable prime lens is in a working state, and the front group and the rear group can be separated when the detachable prime lens is in a non-working state, and the front group descends to meet the purpose of reducing the overall thickness.

The utility model discloses a prime lens. The prime lens comprises a first lens to a ninth lens which are sequentially arranged from the object space to the image space along the optical axis. The first lens is a glass lens with negative focal power, the second lens is a plastic lens with negative focal power, the third lens is a plastic lens with positive focal power, the fourth lens is a glass lens with positive focal power, the fifth lens is a glass lens with positive focal power, the sixth lens is a glass lens with negative focal power, and the seventh lens is a glass lens with positive focal power. The eighth lens is a plastic lens with negative focal power, and the ninth lens is a plastic lens with positive focal power. The prime lens provided by the utility model adopts a 5G4P optical system structure, and by optimizing the shape and focal power of each lens and the relative position of each lens, the aperture number is 0.96-1.091, the total optical length is less than or equal to 22.5 mm, the maximum field angle is 161.28 degrees, and the requirements of large aperture, ultra-wide angle and infrared confocal are met.

The application discloses an inner focusing wide-angle fixed-focus lens, and relates to the technical field of fixed-focus lenses. The inner focusing wide-angle fixed-focus lens comprises, in sequence from an object side to an image side, a first lens group with negative refractive power, a second lens group with positive refractive power, a third lens group with positive refractive power, a fourth lens group with positive refractive power, and a fifth lens group with negative refractive power. In a focusing process, the fourth lens group moves along an optical axis, and the first lens group, the second lens group, the third lens group and the fifth lens group remain unchanged relative to the position of an image surface. While realizing a large aperture, the inner focusing wide-angle fixed-focus lens has a small number of lenses and a compact structure.

The invention discloses a prime lens. The prime lens comprises three lens groups, in the direction of the central axis, the first lens group with positive focal power sequentially comprises two meniscus positive lenses, a pair of meniscus doublet lenses and another pair of doublet lenses, and the second lens group with negative focal power comprises a pair of doublet lenses. And the third lens group with the positive focal power sequentially comprises a set of triplet lens, three pairs of doublet lenses and an aspheric negative lens. During focusing, only the second lens group moves along the central axis. The prime lens adapts to a large aperture, is small in focusing electric power load, and can be used for a full-frame camera.