Externally-mounted macro lens

Abstract

The invention provides a plug-in macro lens which is sequentially composed of a first lens, a second lens, a third lens and a fourth lens from the object side face to the image side face in the optical axis direction, the first lens, the second lens, the third lens and the fourth lens are correspondingly installed in a focusing lens barrel, and the plug-in macro lens is connected with a rear-end main lens through a structural part; the first lens, the second lens and the third lens form a front-end lens group; the fourth lens forms a rear-end lens group; the front-end lens group is set as a fixed lens group, and the rear-end lens group is set as a movable lens group; the first lens has negative focal power, the second lens has negative focal power, the third lens has negative focal power, and the fourth lens has positive focal power; the following conditional expressions are satisfied:-0.25 lt; fg1 / flt; -0.05, 0.05 lt,-0.05, 0.05 lt; fg2 / flt; 0, 0.25,-2.0 lt; fg1 / fg2lt; 0.5 [mu] m, 0.08 [mu] m; | [delta] D | / TTLlt; 0.12, 1.0 lt, 0.12, 1.0 lt; lg1 / Lg2lt; 2.0, 1.0 lt, 2.0, 1.0 lt; cT1 / CT2lt; 2.0, 0.1 lt; cT3 / CT4lt; and 0.3. The main lens matched with the external macro lens can realize clear imaging within the object distance range of 100mm-750mm.

Description

Technical Field

[0001] This invention relates to the field of optical lens technology, and more specifically to an external macro lens. Background Technology

[0002] With technological advancements and rising living standards, cameras and their lenses are increasingly used in everyday life and professional fields. For different shooting scenarios, the market has developed various lenses with specific optical characteristics, such as wide-angle lenses for recording large scenes, macro lenses for capturing details of small objects, and portrait lenses optimized for portrait photography. These lenses are typically designed according to the specific needs of a particular scenario and have relatively fixed optical parameters.

[0003] Currently, most mainstream consumer-grade lenses are prime lenses with fixed apertures and focal lengths. The optical design of these lenses is typically optimized for a specific range of object distances (such as close, medium, or long distances) to ensure sharp images within that range. However, when the object distance changes, especially when maintaining high-quality imaging across a wide range from foreground to background, these prime lenses often struggle to meet the demands. Their inherent optical characteristics result in limited depth of field, potentially leading to blurry images, reduced resolution, or increased aberrations (such as spherical aberration and field curvature) at non-designed object distances. Specifically, current technology struggles to maintain both high image sharpness and a stable field of view across a wide range of object distances, such as 100mm to 750mm. This forces users to frequently change lenses at different shooting distances, impacting both convenience and efficiency, and failing to meet the combined needs of a versatile lens and high-quality imaging.

[0004] Therefore, existing technologies have a significant drawback: the lack of an optical lens solution that can maintain stable, high-resolution imaging without sacrificing the field of view across a wide range of object distances (e.g., from a close distance of 100mm to a distant distance of 750mm). This limits the applicability of cameras in complex and varied scenarios, failing to fully meet users' urgent needs for portability, functional versatility, and high-standard image quality. The industry needs a new imaging lens solution to overcome the aforementioned limitations in depth of field and image quality as object distance changes, thereby improving overall imaging performance and user experience. Summary of the Invention

[0005] To address the above problems, this invention provides an external macro lens that, when paired with a specific main camera lens, can achieve clear imaging within an object distance range of 100mm-750mm without affecting the imaging field of view.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] An external macro lens is composed of a first lens, a second lens, a third lens, and a fourth lens in sequence from the object side to the image side along the optical axis direction. The first lens, the second lens, the third lens, and the fourth lens are correspondingly installed in the focusing lens barrel, and the external macro lens is connected to the rear main lens through a structural member; the first lens, the second lens, and the third lens form a front lens group; the fourth lens forms a rear lens group; the front lens group is set as a fixed lens group, and the rear lens group is set as a moving lens group;

[0008] The first lens has a negative focal power, the second lens has a negative focal power, the third lens has a negative focal power, and the fourth lens has a positive focal power;

[0009] It satisfies the following conditional expressions:

[0010] -0.25 < fg1 / f < -0.05, where fg1 represents the combined focal length of the front lens group, and f represents the effective focal length of the external macro lens;

[0011] 0.05 < fg2 / f < 0.25, where fg2 represents the combined focal length of the rear lens group, and f represents the effective focal length of the macro lens;

[0012] -2.0 < fg1 / fg2 < -0.5, where fg1 represents the combined focal length of the front lens group, and fg2 represents the combined focal length of the rear lens group.

[0013] 0.08 < │ΔD│ / TTL < 0.12, where TTL represents the overall optical length of the macro lens, defined as the distance from the vertex on the object side of the first lens of the external macro lens to the vertex on the object side of the first lens of the rear main lens behind the fourth lens, and ΔD represents the distance that the rear lens group at the rear end of the external macro lens moves in the optical axis direction when the object distance varies within the range of 100 mm to 750 mm.

[0014] 1.0 < Lg1 / Lg2 < 2.0, where Lg1 represents the total length of the front lens group, and Lg2 represents the total length of the rear lens group. The total length of the lens group is defined as the distance from the vertex on the object side of the first lens of the lens group to the vertex on the image side of the last lens.

[0015] 1.0 < CT1 / CT2 < 2.0, 0.1 < CT3 / CT4 < 0.3, where CT1 represents the central thickness of the first lens, CT2 represents the central thickness of the second lens, CT3 represents the central thickness of the third lens, and CT4 represents the central thickness of the fourth lens.

[0016] Preferably, it satisfies the conditional formula 5.0 < │ΔD│ / │ΔIH│ < 12.0, where ΔD represents the distance that the rear lens group at the rear end of the external macro lens moves in the optical axis direction when the object distance varies within the range of 100 mm to 750 mm, and ΔIH represents the difference in image height corresponding to the external macro lens at object distances of 100 mm and 750 mm and a field of view angle FOV = 140°.

[0017] Preferably, the image sides and object sides of the second lens, the third lens, and the fourth lens are all aspherical surfaces.

[0018] The beneficial effects of the present invention are as follows:

[0019] 1. It satisfies the conditional formulas -0.25 < fg1 / f < -0.05, 0.05 < fg2 / f < 0.25, -2.0 < fg1 / fg2 < -0.5. With the position of the front lens group fixed, by adjusting the relative distance between the rear lens group and the front lens group, it is possible to achieve clear imaging of the main lens with an external macro lens within the object distance range of 100 mm - 750 mm.

[0020] 2. It satisfies the conditional formula 0.08 < │ΔD│ / TTL < 0.12, and the purpose of focusing the external macro lens within a short stroke can be achieved.

[0021] 3. It satisfies the conditional formula 5.0 < │ΔD│ / │ΔIH│ < 12.0, which can ensure that the field of view angle remains basically unchanged when the main lens focuses at different object distances with the external macro lens, without affecting the actual imaging effect.

[0022] 4. It satisfies the conditional formulas 1.0 < Lg1 / Lg2 < 2.0, 1.0 < CT1 / CT2 < 2.0, 0.1 < CT3 / CT4 < 0.3, and the requirements of compactness and light weight of the external macro lens system can be achieved. Description of the Drawings

[0023] Figure 1 It is a cross-sectional structure schematic diagram of the first embodiment of the present invention (showing the state of the object distance being 100 mm).

[0024] Figure 2 It is an optical transfer function curve graph of the macro lens when the photography distance is 100 mm in the first embodiment of the present invention.

[0025] Figure 3 It is an astigmatism diagram of the macro lens when the photography distance is 100 mm in the first embodiment of the present invention.

[0026] Figure 4 It is a distortion curve graph of the macro lens when the photography distance is 100 mm in the first embodiment of the present invention.

[0027] Figure 5 This is a cross-sectional structural diagram of the first embodiment of the present invention (showing the state where the photographic object distance is 750mm).

[0028] Figure 6 This is an optical transfer function curve when the macro lens photography distance is 750mm in the first embodiment of the present invention.

[0029] Figure 7 This is an image of astigmatism when the macro lens photography distance is 750mm in the first embodiment of the present invention.

[0030] Figure 8 This is a distortion curve diagram when the macro lens photography distance is 750mm in the first embodiment of the present invention.

[0031] Figure 9 This is a cross-sectional structural diagram of the second embodiment of the present invention (showing the state where the photographic object distance is 100mm).

[0032] Figure 10 This is an optical transfer function curve for a macro lens with a shooting distance of 100mm in the second embodiment of the present invention.

[0033] Figure 11 This is an image of astigmatism when the macro lens photography distance is 100mm in the second embodiment of the present invention.

[0034] Figure 12 This is a distortion curve diagram when the macro lens photography distance is 100mm in the second embodiment of the present invention.

[0035] Figure 13 This is a cross-sectional structural diagram of the second embodiment of the present invention (showing the state where the photographic object distance is 750mm).

[0036] Figure 14 This is an optical transfer function curve for a macro lens with a shooting distance of 750mm in the second embodiment of the present invention.

[0037] Figure 15 This is an image of astigmatism when the macro lens photography distance is 750mm in the second embodiment of the present invention.

[0038] Figure 16 This is a distortion curve diagram when the macro lens photography distance is 750mm in the second embodiment of the present invention.

[0039] Figure 17 This is a cross-sectional structural diagram of the third embodiment of the present invention (showing the state where the photographic object distance is 100mm).

[0040] Figure 18This is an optical transfer function curve for a macro lens with a shooting distance of 100mm in the third embodiment of the present invention.

[0041] Figure 19 This is an image of astigmatism when the macro lens photography distance is 100mm in the third embodiment of the present invention.

[0042] Figure 20 This is a distortion curve diagram when the macro lens photography distance is 100mm in the third embodiment of the present invention.

[0043] Figure 21 This is a cross-sectional structural diagram of the third embodiment of the present invention (showing the state where the photographic object distance is 750mm).

[0044] Figure 22 This is an optical transfer function curve for a macro lens with a shooting distance of 750mm in the third embodiment of the present invention.

[0045] Figure 23 This is an image of astigmatism when the macro lens photography distance is 750mm in the third embodiment of the present invention.

[0046] Figure 24 This is a distortion curve diagram when the macro lens photography distance is 750mm in the third embodiment of the present invention.

[0047] The attached figures are labeled as first lens 11, second lens 12, third lens 13, fourth lens 14, front lens group g1, and rear lens group g2. Detailed Implementation

[0048] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Several embodiments of the invention are illustrated in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

[0049] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0050] In this embodiment, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the position of the convex surface is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the position of the concave surface is not defined, it means that the lens surface is concave at least in the paraxial region. The surface of each lens closest to the object to be photographed is called the object side surface of the lens, and the surface of each lens closest to the imaging surface is called the image side surface of the lens.

[0051] The present invention provides an external macro lens, which is composed of a first lens 11, a second lens 12, a third lens 13, and a fourth lens 14 in sequence from the object side surface to the image side surface along the optical axis direction. The first lens 11, the second lens 12, the third lens 13, and the fourth lens 14 are correspondingly installed in the focusing lens barrel, and the external macro lens is connected to the rear main lens through a structural member; the first lens 11, the second lens 12, and the third lens 13 form a front lens group g1; the fourth lens 14 forms a rear lens group g2; the front lens group g1 is set as a fixed lens group, and the rear lens group g2 is set as a moving lens group;

[0052] The first lens 11 has a negative optical power, the second lens 12 has a negative optical power, the third lens 13 has a negative optical power, and the fourth lens 14 has a positive optical power; the image side surface and the object side surface of the second lens 12, the third lens 13, and the fourth lens 14 are both set as aspherical surfaces.

[0053] It satisfies the following conditional expressions:

[0054] -0.25 < fg1 / f < -0.05, where fg1 represents the combined focal length of the front lens group g1, and f represents the effective focal length of the external macro lens;

[0055] 0.05 < fg2 / f < 0.25, where fg2 represents the combined focal length of the rear lens group g2, and f represents the effective focal length of the macro lens;

[0056] -2.0 < fg1 / fg2 < -0.5, where fg1 represents the combined focal length of the front lens group g1, and fg2 represents the combined focal length of the rear lens group g2.

[0057] Satisfying the above conditional expressions can achieve clear imaging of the main lens equipped with the external macro lens within the object distance range of 100 mm - 750 mm.

[0058] It satisfies the conditional formula: 0.08 < │ΔD│ / TTL < 0.12, where TTL represents the total optical length of the macro lens, which is defined as the distance from the vertex on the object side of the first lens 11 of the external macro lens to the vertex on the object side of the first lens of the main lens behind the fourth lens 14, and ΔD represents the distance that the rear lens group g2 of the external macro lens moves in the optical axis direction when the object distance varies within the range of 100 mm to 750 mm. Satisfying this conditional formula can achieve the purpose of focusing the macro lens within a short stroke.

[0059] It satisfies the conditional formula: 5.0 < │ΔD│ / │ΔIH│ < 12.0, where ΔD represents the distance that the rear lens group g2 of the external macro lens moves in the optical axis direction when the object distance varies within the range of 100 mm to 750 mm, and ΔIH represents the difference in image height corresponding to the external macro lens at object distances of 100 mm and 750 mm and a field angle FOV = 140°. Satisfying this conditional formula can ensure that the field angle of the main lens remains basically unchanged when focusing at different object distances with this macro lens, without affecting the actual imaging effect.

[0060] It satisfies the conditional formulas: 1.0 < Lg1 / Lg2 < 2.0, where Lg1 represents the total length of the front lens group g1, and Lg2 represents the total length of the rear lens group g2. The total length of the lens group is defined as the distance from the vertex on the object side of the first lens of the lens group to the vertex on the image side of the last lens; 1.0 < CT1 / CT2 < 2.0, 0.1 < CT3 / CT4 < 0.3, where CT1 represents the central thickness of the first lens 11, CT2 represents the central thickness of the second lens 12, CT3 represents the central thickness of the third lens 13, and CT4 represents the central thickness of the fourth lens 14. Satisfying the above conditional formulas can meet the requirements of the external macro lens system for compactness and light weight.

[0061] For the first embodiment, please refer to Figures 1-8 As shown, in the first embodiment of the present invention, an external macro lens is provided. The first lens 11 has a negative optical power, and the center of the object side surface is convex, and the center of the image side surface is concave; the second lens 12 has a negative optical power, and the center of the object side surface is convex, and the center of the image side surface is concave; the third lens 13 has a negative optical power, and the center of the object side surface is convex, and the center of the image side surface is concave; the fourth lens 14 has a positive optical power, and the center of the object side surface is convex, and the center of the image side surface is concave. A specific main lens is connected to the external macro lens through a structural member. The relevant parameters of each lens in this embodiment are shown in Table 1-1, the variable interval parameters between the front lens group g1 and the rear lens group g2 of this embodiment and between the macro lens and the main lens are shown in Table 1-2, and the aspheric parameters of each lens of this embodiment are shown in Table 1-3.

[0062] Table 1-1

[0063]

[0064] Table 1-2

[0065]

[0066] Table 1-3

[0067]

[0068] All of the aforementioned aspherical surfaces satisfy the following equation:

[0069]

[0070] Where: z represents the distance of the surface from the vertex of the surface along the optical axis, C represents the curvature of the vertex of the surface, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E, F, G, and H represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients, respectively. The aspherical surfaces in the following examples all follow this formula.

[0071] In the first embodiment, the macro lens optical system has a focal length f = 128.042 mm, a field of view (FOV) of 140 degrees, and a total system length (TTL) of 11.506 mm. Table 1-4 shows the calculated results.

[0072] Table 1-4

[0073] Conditional expression actual result -0.25<fg1 / f<-0.05 -0.096 conform to 0.05<fg2 / f<0.25 0.097 conform to -2.0<fg1 / fg2<-0.5 -0.992 conform to 0.08<│ΔD│ / TTL<0.12 0.097 conform to 5.0<│ΔD│ / │ΔIH│<12.0 10.665 conform to 1.0<Lg1 / Lg2<2.0 1.562 conform to 1.0<CT1 / CT2<2.0 1.294 conform to 0.1<CT3 / CT4<0.3 0.164 conform to

[0074] For the second embodiment, please refer to... Figures 9-16 As shown. The second embodiment of this invention provides an external macro lens. This embodiment has a largely the same lens structure as the first embodiment, but differs in the curvature, surface coefficient, lens spacing, and center thickness of each lens. The first lens 11 has negative optical power, with a convex center on the object side and a concave center on the image side; the second lens 12 has negative optical power, with a convex center on the object side and a concave center on the image side; the third lens 13 has negative optical power, with a convex center on the object side and a concave center on the image side; and the fourth lens 14 has positive optical power, with a convex center on the object side and a concave center on the image side. The first, second, and third lenses form the front lens group g1, and the fourth lens forms the rear lens group g2. A specific main lens is connected to this external macro lens via structural components.

[0075] The relevant parameters of each lens in this embodiment are shown in Table 2-1. The variable interval parameters between the front lens group g1 and the rear lens group g2, and between the macro lens and the main lens in this embodiment are shown in Table 2-2. The parameters of each aspherical lens in this embodiment are shown in Table 2-3.

[0076] Table 2-1

[0077]

[0078] Table 2-2

[0079]

[0080] Table 2-3

[0081]

[0082] All of the aforementioned aspherical surfaces satisfy the following equation:

[0083]

[0084] Where: z represents the distance of the surface from the vertex of the surface along the optical axis, C represents the curvature of the vertex of the surface, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E, F, G, and H represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients, respectively. The aspherical surfaces in the following examples all follow this formula.

[0085] In the second embodiment, the macro lens optical system has a focal length f = 129.442 mm, a field of view (FOV) of 140 degrees, and a total system length (TTL) of 11.409 mm. Table 2-4 shows the calculated results.

[0086] Table 2-4

[0087] Conditional expression actual result -0.25<fg1 / f<-0.05 -0.099 conform to 0.05<fg2 / f<0.25 0.100 conform to -2.0<fg1 / fg2<-0.5 -0.993 conform to 0.08<│ΔD│ / TTL<0.12 0.106 conform to 5.0<│ΔD│ / │ΔIH│<12.0 10.145 conform to 1.0<Lg1 / Lg2<2.0 1.693 conform to 1.0<CT1 / CT2<2.0 1.502 conform to 0.1<CT3 / CT4<0.3 0.193 conform to

[0088] Third embodiment, please refer to Figures 17-24 As shown. The third embodiment of the present invention provides an external macro lens. The lens structure of this embodiment is largely the same as that of the first embodiment, except that the curvature, surface coefficient, lens spacing and lens center thickness of each lens are different. The first lens (11) has negative optical power and the center of the object side is convex and the center of the image side is concave; the second lens (12) has negative optical power and the center of the object side is convex and the center of the image side is concave; the third lens (13) has negative optical power and the center of the object side is convex and the center of the image side is concave; the fourth lens (14) has positive optical power and the center of the object side is convex and the center of the image side is concave. The first lens, the second lens and the third lens form the front lens group (g1) and the fourth lens forms the rear lens group (g2). A specific main lens is connected to the external macro lens through a structural component.

[0089] The relevant parameters of each lens in this embodiment are shown in Table 3-1. The variable interval parameters between the front lens group (g1) and the rear lens group (g2) and between the macro lens and the main lens in this embodiment are shown in Table 3-2. The parameters of each aspherical lens in this embodiment are shown in Table 3-3.

[0090] Table 3-1

[0091]

[0092]

[0093] Table 3-2

[0094]

[0095] Table 3-3

[0096]

[0097] All of the aforementioned aspherical surfaces satisfy the following equation:

[0098]

[0099] Where: z represents the distance of the surface from the vertex of the surface along the optical axis, C represents the curvature of the vertex of the surface, K represents the quadratic surface coefficient, h represents the distance from the optical axis to the surface, and B, C, D, E, F, G, and H represent the fourth, sixth, eighth, tenth, twelfth, fourteenth, and sixteenth order surface coefficients, respectively. The aspherical surfaces in the following examples all follow this formula.

[0100] In the third embodiment, the macro lens optical system has a focal length f = 129.874 mm, a field of view (FOV) of 140 degrees, and a total system length (TTL) of 10.877 mm. Table 3-4 shows the calculated results.

[0101] Table 3-4

[0102] Conditional expression actual result -0.25<fg1 / f<-0.05 -0.087 conform to 0.05<fg2 / f<0.25 0.090 conform to -2.0<fg1 / fg2<-0.5 -0.971 conform to 0.08<│ΔD│ / TTL<0.12 0.090 conform to 5.0<│ΔD│ / │ΔIH│<12.0 6.406 conform to 1.0<Lg1 / Lg2<2.0 1.287 conform to 1.0<CT1 / CT2<2.0 1.258 conform to 0.1<CT3 / CT4<0.3 0.197 conform to

[0103] The above-described embodiments are merely three examples of implementation methods of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. An external micro-lens, which is composed of a first lens (11), a second lens (12), a third lens (13) and a fourth lens (14) in order from the object side to the image side along the optical axis direction, the first lens (11), the second lens (12), the third lens (13) and the fourth lens (14) are installed in the focusing lens barrel correspondingly, and the external micro-lens is connected with the rear main lens through a structural member; characterized in that: The first lens (11), the second lens (12) and the third lens (13) form a front lens group (g1); the fourth lens (14) forms a rear lens group (g2); the front lens group (g1) is arranged as a fixed lens group, and the rear lens group (g2) is arranged as a movable lens group; The first lens (11) has a negative focal power, the second lens (12) has a negative focal power, the third lens (13) has a negative focal power, and the fourth lens (14) has a positive focal power; It satisfies the following conditional expression: -0.25<fg1 / f<-0.05, wherein fg1 represents the combined focal length of the front lens group (g1), and f represents the effective focal length of the external micro-lens; 0.05<fg2 / f<0.25, wherein fg2 represents the combined focal length of the rear lens group (g2), and f represents the effective focal length of the micro-lens; -2.0<fg1 / fg2<-0.5, wherein fg1 represents the combined focal length of the front lens group (g1), and fg2 represents the combined focal length of the rear lens group (g2); 0.08<│ Δ D│ / TTL<0.12, wherein TTL represents the total track length of the macro lens, defined as the distance from the vertex on the object side of the first lens (11) of the macro lens to the vertex on the object side of the first lens of the main lens behind the fourth lens (14), and ΔD represents the distance moved in the direction of the optical axis of the rear end lens group (g2) of the rear end of the macro lens when the object distance ranges from 100mm to 750mm; 1.0<Lg1 / Lg2<2.0, wherein Lg1 represents the total length of the front lens group (g1), Lg2 represents the total length of the rear lens group (g2), and the total length of the lens group is defined as the distance from the first lens object-side vertex to the last lens image-side vertex; 1.0<CT1 / CT2<2.0, 0.1<CT3 / CT4<0.3, wherein CT1 represents the center thickness of the first lens (11), CT2 represents the center thickness of the second lens (12), CT3 represents the center thickness of the third lens (13), and CT4 represents the center thickness of the fourth lens (14).

2. The external micro-lens according to claim 1, characterized in that: which satisfies condition formula 5.0<│ Δ D│ / │ Δ IH│<12.0, wherein ΔD represents the distance moved in the optical axis direction of the rear end lens group (g2) of the rear end of the external micro-lens when the object distance ranges from 100mm to 750mm, and ΔIH represents the corresponding image height difference value of the external micro-lens at 100mm and 750mm object distance respectively and the field of view angle FOV=140°.

3. The external micro-lens according to any one of claims 1 or 2, characterized in that: The image side and object side of the second lens (12), the third lens (13) and the fourth lens (14) are all arranged as aspherical surfaces.

Images