A visual lens

Abstract

The embodiment of the present invention discloses a visual lens. The visual lens comprises: a first lens group, an aperture and a second lens group arranged in sequence along the optical axis; the first lens group comprises a first lens with positive focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with negative focal power, a fifth lens with positive focal power and a sixth lens with positive focal power arranged in sequence from the object side to the image side along the optical axis; the second lens group comprises a seventh lens with positive focal power, an eighth lens with negative focal power, a ninth lens with positive focal power, a tenth lens with positive focal power, an eleventh lens with positive focal power and a twelfth lens with negative focal power arranged in sequence from the object side to the image side along the optical axis. The visual lens provided by the embodiment of the present invention has high resolution, small distortion and long working distance.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of optical imaging technology, and in particular to a visual lens. Background Art

[0002] As the degree of industrial automation increases, the machine vision system has been continuously developed. Machine vision systems are currently widely used in measurement, judgment, automated production and many other aspects.

[0003] The core of the machine vision system is the machine vision lens, and its imaging quality is the most important factor in determining whether the machine vision system is reliable. However, the machine vision lens in the prior art has low pixels, large distortion, and a small field of view. Summary of the invention

[0004] The embodiment of the present invention provides a visual lens to achieve the effects of high resolution, small distortion and long working distance.

[0005] An embodiment of the present invention provides a visual lens, which includes: a first lens group, an aperture, and a second lens group arranged in sequence along an optical axis; the first lens group includes a first lens with positive focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, and a sixth lens with positive focal power, which are arranged in sequence from the object side to the image side along the optical axis;

[0006] The second lens group includes a seventh lens with positive focal power, an eighth lens with negative focal power, a ninth lens with positive focal power, a tenth lens with positive focal power, an eleventh lens with positive focal power and a twelfth lens with negative focal power, which are arranged in sequence from the object side to the image side along the optical axis.

[0007] Optionally, the first lens group includes a fixed lens group; and the second lens group includes a focusing lens group.

[0008] Optionally, the focal lengths of the first lens group and the visual lens satisfy the relationship: 3<|f g / f|<8;

[0009] The focal lengths of the second lens group and the visual lens satisfy the relationship: 1<|f t / f|<4;

[0010] Wherein, f is the focal length of the visual lens, f g is the focal length of the first lens group, f t is the focal length of the second lens group.

[0011] Optionally, the focal lengths of 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 eleventh lens and the twelfth lens respectively satisfy the relationship with the focal length of the visual lens:

[0012] 3.0<|f1 / f|<7.0;

[0013] 1.5<|f2 / f|<3.8;

[0014] 0.9<|f3 / f|<12;

[0015] 1.5<|f4 / f|<5.5;

[0016] 1.6<|f5 / f|<4.0;

[0017] 1.5<|f6 / f|<7.2;

[0018] 0.7<|f7 / f|<2.5;

[0019] 0.4<|f8 / f|<0.9;

[0020] 1.2<|f9 / f|<6.0;

[0021] 0.8<|f 10 / f|<3.2;

[0022] |f 11 / f|>4.5;

[0023] 1.1<|f 12 / f|<3.2;

[0024] Wherein, f is the focal length of the visual lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, f8 is the focal length of the eighth lens, f9 is the focal length of the ninth lens, and f 10 is the focal length of the tenth lens, f 11 is the focal length of the eleventh lens, f 12 is the focal length of the twelfth lens.

[0025] Optionally, the fourth lens and the fifth lens constitute a first cemented lens.

[0026] Optionally, the seventh lens and the eighth lens constitute a second cemented lens.

[0027] Optionally, the Abbe number of the seventh lens and the Abbe number of the eighth lens satisfy the relationship: |vd7-vd8|>30; wherein vd7 is the Abbe number of the seventh lens, and vd8 is the Abbe number of the eighth lens.

[0028] 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 eleventh lens and the twelfth lens are all glass lenses.

[0029] 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 eleventh lens and the twelfth lens are all glass spherical lenses.

[0030] The visual lens provided by the embodiment of the present invention is provided with a first lens group, an aperture and a second lens group arranged in sequence along the optical axis; wherein the first lens group includes a first lens with positive focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with negative focal power, a fifth lens with positive focal power and a sixth lens with positive focal power arranged in sequence from the object side to the image side along the optical axis; and the second lens group includes a seventh lens with positive focal power, an eighth lens with negative focal power, a ninth lens with positive focal power, a tenth lens with positive focal power, an eleventh lens with positive focal power and a twelfth lens with negative focal power arranged in sequence from the object side to the image side along the optical axis, so as to solve the problems of low pixel, large distortion and small field angle of the visual lens in the prior art, and achieve the effects of high resolution, small distortion and long working distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a structural schematic diagram of a visual lens provided by an embodiment of the present invention;

[0032] Figure 2 is a schematic diagram of the structure of another visual lens provided by an embodiment of the present invention;

[0033] Figure 3 yes Figure 2 Field curvature diagrams of the visual lenses 486nm, 588nm, and 656nm are shown;

[0034] Figure 4 yes Figure 2 The distortion diagram of the visual lens 588nm is shown;

[0035] Figure 5 yes Figure 2Axial aberration diagrams of the visual lens at 486nm, 588nm, and 656nm are shown;

[0036] Figure 6 yes Figure 2 The vertical axis chromatic aberration diagram of the visual lens 486nm, 588nm, and 656nm is shown;

[0037] Figure 7 yes Figure 1 Field curvature diagrams of the visual lenses 486nm, 588nm, and 656nm are shown;

[0038] Figure 8 yes Figure 1 The distortion diagram of the visual lens 588nm is shown;

[0039] Fig. 9 yes Figure 1 Axial aberration diagrams of the visual lens at 486nm, 588nm, and 656nm are shown;

[0040] Fig.10 yes Figure 1 The vertical axis chromatic aberration diagram of the visual lens 486nm, 588nm, and 656nm is shown. DETAILED DESCRIPTION

[0041] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0042] Figure 1 is a schematic diagram of the structure of a visual lens provided by an embodiment of the present invention, such as Figure 1 As shown, the visual lens provided by the embodiment of the present invention includes: a first lens group 10, an aperture 20 and a second lens group 30 arranged in sequence along the optical axis; the first lens group 10 includes a first lens 11 with positive focal power, a second lens 12 with negative focal power, a third lens 13 with negative focal power, a fourth lens 14 with negative focal power, a fifth lens 15 with positive focal power and a sixth lens 16 with positive focal power arranged in sequence from the object side to the image side along the optical axis; the second lens group 30 includes a seventh lens 31 with positive focal power, an eighth lens 32 with negative focal power, a ninth lens 33 with positive focal power, a tenth lens 34 with positive focal power, an eleventh lens 35 with positive focal power and a twelfth lens 36 with negative focal power arranged in sequence from the object side to the image side along the optical axis.

[0043] Among them, the optical focal length is equal to the difference between the convergence of the image-side light beam and the convergence of the object-side light beam, and it characterizes the ability of the optical system to deflect light. The larger the absolute value of the optical focal length, the stronger the ability to bend light, and the smaller the absolute value of the optical focal length, the weaker the ability to bend light. When the optical focal length is a positive number, the refraction of light is convergent; when the optical focal length is a negative number, the refraction of light is divergent. The optical focal length can be used to characterize a certain refractive surface of a lens (i.e., a surface of a lens), can be used to characterize a certain lens, and can also be used to characterize a system formed by multiple lenses (i.e., a lens group). In this embodiment, each lens can be fixed to a lens barrel ( Figure 1 (not shown) by reasonably distributing the optical focal length of the lens, the visual lens imaging effect is good.

[0044] In this embodiment, the first lens group 10 has a compensation effect, the second lens group 30 has a focusing effect, and the aperture 20 has a function of adjusting the intensity of the light beams received by the first lens group 10 and the second lens group 30 to improve the imaging quality. By reasonably allocating the optical power of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 31, the eighth lens 32, the ninth lens 33, the tenth lens 34, the eleventh lens 35 and the twelfth lens 36, the full field optical distortion of the visual lens provided by the embodiment of the present invention is less than 1%, the minimum resolution size of the image plane is less than 2μm, and good imaging quality is maintained at all working distances to meet different measurement requirements.

[0045] The technical solution of this embodiment is to provide a first lens group, an aperture and a second lens group arranged in sequence along the optical axis; wherein the first lens group includes a first lens with positive focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with negative focal power, a fifth lens with positive focal power and a sixth lens with positive focal power arranged in sequence from the object side to the image side along the optical axis; and the second lens group includes a seventh lens with positive focal power, an eighth lens with negative focal power, a ninth lens with positive focal power, a tenth lens with positive focal power, an eleventh lens with positive focal power and a twelfth lens with negative focal power arranged in sequence from the object side to the image side along the optical axis, so as to solve the problems of low pixel, large distortion and small field angle of the visual lens in the prior art and achieve the effects of high resolution, small distortion and long working distance.

[0046] Optionally, continue to see Figure 1 The first lens group 10 includes a fixed lens group; the second lens group 30 includes a focusing lens group.

[0047] Specifically, when the working distance changes, the focusing lens group moves back and forth relative to the fixed lens group to focus, thereby finding the best imaging surface and improving the imaging quality.

[0048] Optionally, continue to see Figure 1 , the focal lengths of the first lens group 10 and the visual lens satisfy the relationship: 3<|f g / f|<8; the focal lengths of the second lens group 30 and the visual lens satisfy the relationship: 1<|f t / f|<4; where f is the focal length of the visual lens, f g is the focal length of the first lens group 10, f t is the focal length of the second lens group 30.

[0049] Optionally, continue to see Figure 1 , the focal lengths of the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 31, the eighth lens 32, the ninth lens 33, the tenth lens 34, the eleventh lens 35 and the twelfth lens 36 and the focal length of the visual lens respectively satisfy the relationship: 3.0<|f1 / f|<7.0; 1.5<|f2 / f|<3.8; 0.9<|f3 / f|<12; 1.5<|f4 / f|<5.5; 1.6<|f5 / f|<4.0; 1.5<|f6 / f|<7.2; 0.7<|f7 / f|<2.5; 0.4<|f8 / f|<0.9; 1.2<|f9 / f|<6.0; 0.8<|f 10 / f|<3.2;|f 11 / f|>4.5;1.1<|f 12 / f|<3.2; wherein f is the focal length of the visual lens, f1 is the focal length of the first lens 11, f2 is the focal length of the second lens 12, f3 is the focal length of the third lens 13, f4 is the focal length of the fourth lens 14, f5 is the focal length of the fifth lens 15, f6 is the focal length of the sixth lens 16, f7 is the focal length of the seventh lens 31, f8 is the focal length of the eighth lens 32, f9 is the focal length of the ninth lens 33, and f 10 is the focal length of the tenth lens 34, f 11 is the focal length of the eleventh lens 35, f 12 is the focal length of the twelfth lens 36.

[0050] The lens parameters described above can be coordinated with each other. On the one hand, the light line of the light beam is adjusted by the focal length of each lens, ultimately achieving high resolution and small distortion; on the other hand, the focal length of each lens is adjusted so that the visual lens maintains good imaging quality at the full working distance to adapt to different measurement requirements.

[0051] Optionally, continue to see Figure 1The fourth lens 14 and the fifth lens 15 form a first cemented lens. The advantages of this arrangement are that, on the one hand, it can be used to correct chromatic aberration and improve imaging quality; on the other hand, it can further reduce the volume of the visual lens and achieve miniaturization.

[0052] It should be noted that the fourth lens 14 and the fifth lens 15 can form a first cemented lens, such as Figure 1 As shown; the fourth lens 14 and the fifth lens 15 can also be arranged separately, which is not specifically limited in this embodiment. Optionally, Figure 2 is a schematic diagram of the structure of another visual lens provided by an embodiment of the present invention, such as Figure 2 As shown, the fourth lens 14 and the fifth lens 15 are arranged separately.

[0053] Optionally, continue to see Figure 1 The seventh lens 31 and the eighth lens 32 form a second cemented lens. The advantages of this arrangement are that, on the one hand, it can be used to correct chromatic aberration and improve imaging quality; on the other hand, it can further reduce the volume of the visual lens and achieve miniaturization.

[0054] On the basis of the above scheme, optionally, continue to refer to Figure 1 , the Abbe number of the seventh lens 31 and the Abbe number of the eighth lens 32 satisfy the relationship: |vd7-vd8|>30; wherein vd7 is the Abbe number of the seventh lens 31, and vd8 is the Abbe number of the eighth lens 32.

[0055] Specifically, when |vd7-vd8|>30, it can be ensured that the seventh lens 31 and the eighth lens 32 are low dispersion lenses. Using lenses with lower dispersion for further chromatic aberration correction can improve the chromatic aberration correction capability to a certain extent, thereby improving the imaging quality of the visual lens.

[0056] Optionally, continue to see Figure 1 The first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 31, the eighth lens 32, the ninth lens 33, the tenth lens 34, the eleventh lens 35 and the twelfth lens 36 are all glass lenses.

[0057] Exemplarily, the first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 31, the eighth lens 32, the ninth lens 33, the tenth lens 34, the eleventh lens 35 and the twelfth lens 36 can all be made of glass materials. In this way, the temperature stability of the glass lens can be used to ensure the stable performance of the visual lens in high and low temperature environments.

[0058] Optionally, continue to see Figure 1The first lens 11, the second lens 12, the third lens 13, the fourth lens 14, the fifth lens 15, the sixth lens 16, the seventh lens 31, the eighth lens 32, the ninth lens 33, the tenth lens 34, the eleventh lens 35 and the twelfth lens 36 are all glass spherical lenses. In this way, the performance of the visual lens is guaranteed to be stable in high and low temperature environments, while also reducing the cost of the visual lens.

[0059] The visual lens provided by the embodiment of the present invention will be further described below with reference to specific examples. It should be noted that the following examples do not constitute a limitation to the present application.

[0060] Exemplary: Continue to see Figure 2 , in this embodiment, Figure 2 The curvature radius, center thickness (i.e., the distance between the center points of adjacent mirror surfaces), refractive index, and Abbe number of each lens along the optical axis from the object side to the image side in the visual lens shown meet the conditions listed in Table 1:

[0061] Table 1 shows a design value of the visual lens (f=8.0mm; aperture F2.4):

[0062] Surface number Radius of curvature thickness refraction Abbe number S1 30.01 4.00 1.62 60.4 S2 238.44 0.10 S3 23.11 0.80 1.83 42.7 S4 9.85 3.67 S5 80.79 0.80 1.92 20.9 S6 14.60 2.17 S7 -18.39 0.80 1.62 60.4 S8 32.32 0.66 S9 100.00 5.33 1.92 20.9 S10 -20.72 0.10 S11 28.53 5.04 1.83 42.7 S12 84.56 6.44 STO PL 2.43 S14 10.36 3.20 1.50 81.6 S15 -5.27 0.80 1.83 42.7 S16 20.64 1.00 S17 25.09 3.50 1.50 81.6 S18 -6.83 0.10 S19 18.42 2.50 1.83 42.7 S20 -51.93 0.10 S21 100.00 2.00 1.83 42.7 S22 620.67 1.50 S23 -8.85 0.80 1.83 42.7 S24 -30.40 3.73 S25 PL 1.65 1.52 64.2 S26 PL 5.34

[0063] The surface numbers in Table 1 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens 11, "S2" represents the back surface of the first lens 12, and so on; the radius of curvature represents the curvature of the lens surface, a positive value represents that the surface is bent toward the image plane, and a negative value represents that the surface is bent toward the object plane, where "PL" represents 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, and a blank 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, and a blank space represents that the current position is air.

[0064] in, Figure 3 yes Figure 2 Field curvature diagrams of the visual lenses 486nm, 588nm, and 656nm are shown; Figure 4 yes Figure 2 The distortion diagram of the visual lens 588nm is shown; Figure 5 yes Figure 2 Axial aberration diagrams of the visual lens at 486nm, 588nm, and 656nm are shown; Figure 6 yes Figure 2 The vertical axis chromatic aberration diagram of the visual lens 486nm, 588nm, and 656nm is shown. Figure 3It can be seen that the field curvature of the visual lens provided in this embodiment is small, that is, when imaging, the difference between the image quality at the center and the image quality at the periphery is small. Figure 4 It can be seen that the optical distortion of the visual lens provided by this embodiment is small in the whole field of view. Figure 5 and Figure 6 It can be seen that the visual lens provided in this embodiment has small axial aberration and small vertical chromatic aberration. Figure 3 , Figure 4 , Figure 5 and Figure 6 It can be seen that the visual lens provided by the embodiment of the present invention has good imaging quality, small optical distortion in the entire field of view, high resolution, and maintains good imaging quality at all working distances.

[0065] For example, see Figure 1 , in this embodiment, Figure 1 The curvature radius, center thickness (i.e., the distance between the center points of adjacent mirror surfaces), refractive index, and Abbe number of each lens along the optical axis from the object side to the image side in the lens shown meet the conditions listed in Table 2:

[0066] Table 2 shows another design value of the visual lens (f=8.0mm; aperture F2.4):

[0067]

[0068]

[0069] The surface numbers in Table 2 are numbered according to the order of the surfaces of each lens, where "S1" represents the front surface of the first lens, "S2" represents the back surface of the first lens, and so on; the radius of curvature represents the degree of curvature of the lens surface, a positive value represents that the surface is bent toward the image side, and a negative value represents that the surface is bent toward the object side, where "PL" represents 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, and a blank 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, and a blank space represents that the current position is air.

[0070] Figure 7 yes Figure 1 Field curvature diagrams of the visual lenses 486nm, 588nm, and 656nm are shown; Figure 8 yes Figure 1 The distortion diagram of the visual lens 588nm is shown; Fig. 9 yes Figure 1 Axial aberration diagrams of the visual lens at 486nm, 588nm, and 656nm are shown; Fig.10 yes Figure 1The vertical axis chromatic aberration diagram of the visual lens 486nm, 588nm, and 656nm is shown. Figure 7 It can be seen that the field curvature of the visual lens provided in this embodiment is small, and when imaging, the difference between the image quality at the center and the image quality at the periphery is small. Figure 8 It can be seen that the optical distortion of the visual lens provided by this embodiment is small in the whole field of view. Fig. 9 and Fig.10 It can be seen that the visual lens provided in this embodiment has small axial aberration and small vertical chromatic aberration. Figure 7 , Figure 8 , Fig. 9 and Fig.10 It can be seen that the visual lens provided by the embodiment of the present invention has good imaging quality, small optical distortion in the entire field of view, high resolution, and maintains good imaging quality at all working distances.

[0071] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection 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, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A visual lens, characterized in that: include: A first lens group, a stop, and a second lens group are sequentially arranged along the optical axis; the first lens group includes a first lens with positive focal power, a second lens with negative focal power, a third lens with negative focal power, a fourth lens with negative focal power, a fifth lens with positive focal power, and a sixth lens with positive focal power, which are sequentially arranged along the optical axis from the object side to the image side; The second lens group includes a seventh lens with positive focal power, an eighth lens with negative focal power, a ninth lens with positive focal power, a tenth lens with positive focal power, an eleventh lens with positive focal power and a twelfth lens with negative focal power, which are arranged in sequence from the object side to the image side along the optical axis.

2. The visual lens according to claim 1, characterized in that: The first lens group includes a fixed lens group; the second lens group includes a focusing lens group.

3. The visual lens according to claim 1, characterized in that: The focal lengths of the first lens group and the visual lens satisfy the relationship: 3<|f g / f|<8; The focal lengths of the second lens group and the visual lens satisfy the relationship: 1<|f t / f|<4; Wherein, f is the focal length of the visual lens, f g is the focal length of the first lens group, f t is the focal length of the second lens group.

4. The visual lens according to claim 1, characterized in that: The focal lengths of 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 eleventh lens and the twelfth lens respectively satisfy the relationship with the focal length of the visual lens: 3.0<|f1 / f|<7.0; 1.5<|f2 / f|<3.8; 0.9<|f3 / f|<12; 1.5<|f4 / f|<5.5; 1.6<|f5 / f|<4.0; 1.5<|f6 / f|<7.2; 0.7<|f7 / f|<2.5; 0.4<|f8 / f|<0.9; 1.2<|f9 / f|<6.0; 0.8<|f 10 / f|<3.2; |f 11 / f|>4.5; 1.1<|f 12 / f|<3.2; Wherein, f is the focal length of the visual lens, f1 is the focal length of the first lens, f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, f5 is the focal length of the fifth lens, f6 is the focal length of the sixth lens, f7 is the focal length of the seventh lens, f8 is the focal length of the eighth lens, f9 is the focal length of the ninth lens, and f 10 is the focal length of the tenth lens, f 11 is the focal length of the eleventh lens, f 12 is the focal length of the twelfth lens.

5. The visual lens according to claim 1, characterized in that: The fourth lens and the fifth lens constitute a first cemented lens.

6. The visual lens according to claim 1, characterized in that: The seventh lens and the eighth lens constitute a second cemented lens.

7. The visual lens according to claim 6, characterized in that: The Abbe number of the seventh lens and the Abbe number of the eighth lens satisfy the relationship: |vd7-vd8|>30; wherein vd7 is the Abbe number of the seventh lens, and vd8 is the Abbe number of the eighth lens.

8. The visual 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 eleventh lens and the twelfth lens are all glass lenses.

9. The visual lens according to claim 8, 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 eleventh lens and the twelfth lens are all glass spherical lenses.

Images