CN106646837A - Fisheye lens - Google Patents

Abstract

The invention provides a novel fisheye lens. The fisheye lens has an eight-group ten-lens structure, wherein two bonded lens groups are included; the first bonding lens group is formed by bonding a fourth lens and a fifth lens along the direction of an optical axis from an object to an imaging end, and the second bonding lens group is formed by bonding a sixth lens and a seventh lens. This fisheye lens makes the correction to the purple fringed, has optimized optical structure, and the dispersion from high to low through ten lenses is mutually arranged, has great improvement to the chromatic aberration, corrects the purple fringed after the formation of image for the purple fringed scope of formation of image than the first edition product is littleer.

Description

Fisheye lens

technical field

The invention relates to a fisheye lens.

Background technique

Fisheye lens is a special kind of ultra-wide-angle lens, and its angle of view usually exceeds the range that the human eye can see. Therefore, there is a big difference between the fisheye lens and the real world scene in the human eye. The world seen by the human eye in real life is a regular and fixed shape, while the picture effect produced by the fisheye lens has various distortions. In general, a fisheye lens can be understood as an ultra-wide-angle lens without image distortion correction. This feature allows the angle of view of the fisheye lens to be designed to be close to or equal to 180°.

Due to no distortion correction, the fisheye lens structure can avoid the use of special lenses, such as aspherical lenses, low dispersion lenses, lens coatings and other high-cost materials or lenses, which makes fisheye lenses cheaper than ultra-wide-angle lenses. The manufacturing cost, which is manifested in that the use of a spherical mirror can basically meet the requirements of the optical system of the fisheye lens.

After entering the digital age, during the shooting process of digital cameras, due to the large light contrast of the subject, the color spots appearing at the junction of the high light and low light parts are mostly purple (or other colors), which are called "purple fringing". ". In the film era, purple fringing was hardly a problem. But in the digital age, purple fringing has become a prominent problem.

There are many reasons for purple fringing, and the control of dispersion by the lens is an important means to reduce purple fringing. Due to the inherent structural characteristics of the ultra-wide-angle lens itself, there is an uneven luminous flux between the center and edge of the image due to the lens design, resulting in more obvious purple fringing.

Therefore, the digital age requires a low-cost fisheye lens that can optimize purple fringing.

Invention content:

The purpose of the present invention is to provide a novel fisheye lens.

The fisheye lens has an eight-group ten-lens lens structure, which includes two cemented lens groups; along the optical axis direction from the object to the imaging end, the first cemented lens group is cemented by the fourth and fifth lenses. The second cemented lens group is formed by cementing the sixth and seventh lenses.

The effective focal length of the second cemented lens group of the fisheye lens is 15 mm.

The sixth lens is a glass lens with a refractive index of 1.78-1.90, its dispersion coefficient is 20-30, its focal length is 8mm, the curvature radius of R1 surface is 4-6, and the curvature radius of R2 surface is -6--10. The refractive index of the sixth lens is preferably 1.83, and its dispersion coefficient is preferably 26.

The seventh lens is a glass lens with a refractive index of 1.78-1.95; its dispersion coefficient is 20-30, its focal length is -8mm, the curvature radius of R1 surface is 3-6; the curvature radius of R2 surface is -10--15. The refractive index of the seventh lens is preferably 1.80, and its dispersion coefficient is preferably 25.

The eighth lens of the fisheye lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, its focal length is -10mm, the radius of curvature of the R1 surface is 15-20, and the curvature radius of the R2 surface is 3-6. The eighth lens is preferably a glass lens with a refractive index of 1.88, and its dispersion coefficient is preferably 25.

The effective focal length of the first cemented lens group of the fisheye lens is 12mm.

The fourth lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, its focal length is -10 mm, the R1 surface is a plane, and the R2 surface has a curvature radius of 3-6. The refractive index of the fourth lens is preferably 1.86, and its dispersion coefficient is preferably 25.

The fifth lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, its focal length is 4mm, the curvature radius of R1 surface is 3-6, and the curvature radius of R2 surface is -10--15. The refractive index of the fifth lens is preferably 1.90, and its dispersion coefficient is preferably 25.

The first lens of the fisheye lens is a glass lens with a refractive index of 1.5-1.6, its dispersion coefficient is 70-75, the focal length is -15mm, the radius of curvature of the R1 surface is 15-18, and the curvature radius of the R2 surface is 8-10. The refractive index of the first lens is preferably 1.55, and its dispersion coefficient is preferably 72.

The second lens of the fisheye lens is a glass lens with a refractive index of 1.75-1.90, its dispersion coefficient is 40-50, the focal length is -8mm, the radius of curvature of the R1 surface is 15-20, and the curvature radius of the R2 surface is 3-6. The refractive index of the second lens is preferably 1.80, and its dispersion coefficient is preferably 45.

The third lens of the fisheye lens is a glass lens with a refractive index of 1.80-1.85, the dispersion coefficient is 30-35, the focal length is -7mm, the curvature radius of the R1 surface is -10--12, and the curvature radius of the R2 surface is 4-10 . The refractive index of the third lens is preferably 1.82, and its dispersion coefficient is preferably 34.

The ninth lens of the fisheye lens is a glass lens with a refractive index of 1.70-1.80, its dispersion coefficient is 50-60, the focal length is 7mm, the curvature radius of the R1 surface is 15-20, and the curvature radius of the R2 surface is -10--15 . The refractive index of the ninth lens is preferably 1.75, and its dispersion coefficient is preferably 55.

The tenth lens of the fisheye lens is a glass lens with a refractive index of 1.40-1.55, a dispersion coefficient of 70-80, a focal length of 8 mm, a curvature radius of R1 of 3-6, and a plane of R2. The refractive index of the tenth lens is preferably 1.55, and the dispersion coefficient is preferably 75.

Description of drawings

FIG. 1 is a schematic structural view of the optical system of the fisheye lens of the present invention.

Figure 2 is the first version of the color difference diagram (the maximum value in the 0.43nm band is above 10).

Figure 3 is the second version of the chromatic aberration diagram (the maximum value in the 0.43nm band is around 3).

Figure 4 is a 230° MTF curve.

Fig. 5 is a 230°DIST curve diagram.

Figure 6 is a 230° sharpness curve.

detailed description:

As shown in Figures 1-6, in order to make the purpose, technical solution and advantages of the present invention more clear. The present invention will be described in detail in combination with specific embodiments. During this process, descriptions of known structures and technologies are omitted to avoid unnecessarily confusing the concept of the present invention. These descriptions are exemplary only. It is not intended to limit the scope of the invention.

The fisheye lens has an eight-group ten-lens lens structure, which includes two cemented lens groups; along the optical axis direction from the object to the imaging end, the first cemented lens group is cemented by the fourth and fifth lenses. The second cemented lens group is formed by cementing the sixth and seventh lenses.

Each lens adopts different refractive index materials, so that the light changes, so that the resolution is optimal; the details are as follows:

The first lens 1 is a glass material with a lower refractive index and a higher dispersion coefficient; (the refractive index range is 1.5-1.6, preferably around 1.55; the dispersion coefficient range is 70-75, preferably around 72) Focal length: f=-15mm Radius of curvature: R1 surface 15 ‐18; R2 side 8‐10.

The second lens 2 is a glass material with a higher refractive index and a lower dispersion coefficient; (the range of refractive index is 1.75-1.90, preferably about 1.80; the range of dispersion coefficient is 40-50, preferably about 45) Focal length: f=-8mm Radius of curvature: R1 surface 15 ‐20; R2 face 3‐6.

The third lens 3 is a glass material with a higher refractive index and a lower dispersion coefficient; (the range of refractive index is 1.8-1.85, preferably about 1.82; the range of dispersion coefficient is 30-35, preferably about 34) Focal length: f=-7mm Radius of curvature: R1 surface- 10～‐12; R2 surface 4‐10.

The fourth lens 4 is a glass material with a lower refractive index and a higher dispersion coefficient; (the refractive index range is 1.78-1.95, preferably about 1.86; the dispersion coefficient range is 20-30, preferably about 25) focal length: f=4mm radius of curvature: R1 surface 3- 6; R2 surface ‐10～‐15.

The fourth and fifth lenses are cemented lenses. Focal length: f=12mm.

The sixth lens 6 is glass material with higher refractive index and lower dispersion coefficient; (refractive index range 1.78-1.90 is preferably about 1.83

Right; the dispersion coefficient range is 20-30, preferably around 26) focal length: f=8mm radius of curvature: R1 plane 4-6; R2 plane -6--10.

The seventh lens 7 is a glass material with a higher refractive index and a lower dispersion coefficient; (the range of refractive index is 1.78-1.95, preferably about 1.80; the range of dispersion coefficient is 20-30, preferably about 25) Focal length: f=-8mm Radius of curvature: R1 surface 3 ‐6; R2 surface ‐10～‐15.

The sixth and seventh lenses are cemented lenses. Focal length: f=15mm.

The eighth lens 8 is glass material with higher refractive index and lower dispersion coefficient; (refractive index range is 1.78-1.95, preferably about 1.88; dispersion coefficient range is 20-30, preferably about 25) focal length: f=-10mm radius of curvature: R1 surface 15 ‐20; R2 face 3‐6.

The ninth lens 9 is a glass material with moderate refractive index and moderate dispersion coefficient; (the range of refractive index is 1.70-1.80, preferably about 1.75; the range of dispersion coefficient is 50-60, preferably about 55) focal length: f=7mm radius of curvature: R1 surface 15-20; R2 surface ‐10～‐15.

The tenth lens 10 is a glass material with a lower refractive index and a higher dispersion coefficient; (the range of refractive index is 1.40-1.55, preferably about 1.55; the range of dispersion coefficient is 70-80, preferably about 75) Focal length: f=8mm Radius of curvature: R1 surface 3- 6; R2 surface plane.

100 is an imaging plane, that is, a photosensitive element.

Comparing Figure 2 and Figure 3, it can be clearly seen that the chromatic aberration of the latter has been greatly improved.

The purple fringing is corrected, the optical structure is optimized, and the purple fringing after imaging is corrected through the matching of ten lenses from high to low dispersion, making the imaging purple fringing range smaller than that of the first version of the product.

Claims (23)

1. a fisheye lens is characterized in that it has eight groups of ten lens structures, wherein two cemented lens groups are included; along its optical axis direction from object to imaging end, the first cemented lens group is formed by the fourth It is formed by cementing the fifth lens, and the second cemented lens group is formed by cementing the sixth and seventh lenses. 2. The fisheye lens according to claim 1, wherein the effective focal length of the second cemented lens group is 15 mm. 3. The fisheye lens according to claim 1 or 2, wherein the sixth lens is a glass lens with a refractive index of 1.78-1.90, its dispersion coefficient is 20-30, the focal length is 8 mm, and the radius of curvature of the R1 surface is 4‐6, and the radius of curvature of the R2 surface is ‐6～‐10. 4. The fisheye lens according to claim 3, wherein the sixth lens is a glass lens with a refractive index of 1.83, and its dispersion coefficient is 26. 5. The fisheye lens according to claim 1 or 2, wherein the seventh lens is a glass lens with a refractive index of 1.78-1.95; its dispersion coefficient is 20-30, its focal length is -8mm, and the R1 surface curvature The radius is 3‐6; the radius of curvature of the R2 surface is ‐10～‐15. 6. The fisheye lens according to claim 5, wherein the seventh lens is a glass lens with a refractive index of 1.80, and its dispersion coefficient is 25. 7. The fisheye lens according to claim 1, wherein the eighth lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, its focal length is -10mm, and the radius of curvature of the R1 surface is 15‐20, and the radius of curvature of the R2 surface is 3‐6. 8. The fisheye lens according to claim 1 or 7, wherein the eighth lens is a glass lens with a refractive index of 1.88, and its dispersion coefficient is 25. 9. The fisheye lens according to claim 1, wherein the effective focal length of the first cemented lens group is 12mm. 10. The fisheye lens according to claim 1 or 9, wherein the fourth lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, its focal length is -10 mm, and the R1 surface is plane, the R2 surface curvature radius is 3‐6. 11. The fisheye lens according to claim 10, wherein the fourth lens is a glass lens with a refractive index of 1.86, and its dispersion coefficient is 25. 12. The fisheye lens according to claim 1 or 9, wherein the fifth lens is a glass lens with a refractive index of 1.78-1.95, its dispersion coefficient is 20-30, the focal length is 4 mm, and the radius of curvature of the R1 surface is 3‐6, and the radius of curvature of the R2 surface is ‐10～‐15. 13. The fisheye lens according to claim 12, wherein the fifth lens is a glass lens with a refractive index of 1.90, and its dispersion coefficient is 25. 14. The fisheye lens according to claim 1, 2, 7 or 9, wherein the first lens is a glass lens with a refractive index of 1.5-1.6, its dispersion coefficient is 70-75, and its focal length is- 15mm, the radius of curvature of the R1 surface is 15-18, and the radius of curvature of the R2 surface is 8-10. 15. The fisheye lens according to claim 14, wherein the first lens is a glass lens with a refractive index of 1.55, and its dispersion coefficient is 72. 16. The fisheye lens according to claim 1, 2, 7 or 9, wherein the second lens is a glass lens with a refractive index of 1.75-1.90, its dispersion coefficient is 40-50, and its focal length is- 8mm, the radius of curvature of the R1 surface is 15-20, and the radius of curvature of the R2 surface is 3-6. 17. The fisheye lens according to claim 16, wherein the second lens is a glass lens with a refractive index of 1.80, and its dispersion coefficient is 45. 18. The fisheye lens according to claim 1, 2, 7 or 9, wherein the third lens is a glass lens with a refractive index of 1.80-1.85, a dispersion coefficient of 30-35, and a focal length of -7mm , the radius of curvature of the R1 surface is -10--12, and the radius of curvature of the R2 surface is 4-10. 19. The fisheye lens according to claim 18, wherein the third lens is a glass lens with a refractive index of 1.82, and its dispersion coefficient is 34. 20. The fisheye lens according to claim 1, 2, 7 or 9, wherein the ninth lens is a glass lens with a refractive index of 1.70-1.80, its dispersion coefficient is 50-60, and its focal length is 7mm , the R1 surface curvature radius is 15‐20, and the R2 surface curvature radius is ‐10～‐15. 21. The fisheye lens according to claim 20, wherein the ninth lens is a glass lens with a refractive index of 1.75, and its dispersion coefficient is 55. 22. The fisheye lens according to claim 1, 2, 7 or 9, wherein the tenth lens is a glass lens with a refractive index of 1.40-1.55, a dispersion coefficient of 70-80, a focal length of 8mm, and an R1 The surface curvature radius is 3‐6, and the R2 surface is flat. 23. The fisheye lens according to claim 22, wherein the tenth lens is a glass lens with a refractive index of 1.55 and a dispersion coefficient of 75.