Ultra-thin lens for single-lens reflex camera

Abstract

The present invention relates to an ultra-thin lens for a single-lens reflex camera, comprising 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 arranged in sequence from the object side to the image side; the first lens is a double concave lens with a negative focal length; the second lens is a meniscus lens with a positive focal length, with a convex surface facing the object side; the third lens is a double convex lens with a positive focal length; the fourth lens is a double convex lens with a positive focal length; the fifth lens is a double concave lens with a negative focal length; the sixth lens is a meniscus lens with a positive focal length, with a concave surface facing the object side; the seventh lens is a double concave lens with a negative focal length; the eighth lens is a double convex lens with a positive focal length; the ninth lens is a double convex lens with a positive focal length; and the tenth lens is a double concave lens with a negative focal length. The lens of the present invention has the advantages of ultra-high resolution, large aperture and ultra-thinness.

Description

Technical Field

[0001] The invention relates to an ultra-thin lens for a single-lens reflex camera, belonging to the technical field of optical imaging. Background Art

[0002] In digital camera equipment, there is a certain gap in the production and design of domestic lenses. With the improvement of people's living standards, the number of photography enthusiasts has increased, and the demand in this area has also increased. In the existing full-frame lens design, such as the 35mm lens produced by Nikon, Canon, Sigma and other manufacturers, the maximum aperture is only F1.4, the cost performance is low, and the domestic manufacturers' designs are generally based on full glass spherical surfaces, which cannot correct aberrations well. They can only achieve the use effect by relaxing the lens length and increasing the number of lenses. The disadvantages of this type of lens are large size and heavy weight, which is very inconvenient to carry. For example, patent 201610346001 discloses a super-large aperture wide-angle lens for SLR cameras. The disadvantages of its technical solution are: the lens length is too long, reaching 135mm; the lens diameter is relatively large, generally 40-50mm; the number of lenses is large. Therefore, it is necessary to design an ultra-thin, large-light-throughput full-frame lens. Summary of the invention

[0003] The object of the present invention is to provide an ultra-thin lens for a single-lens reflex camera, and the specific scheme is as follows:

[0004] A super-thin lens for a single-lens reflex camera 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 arranged in sequence from the object side to the image side; the first lens is a double concave lens with a negative focal length; the second lens is a meniscus lens with a positive focal length, with a convex surface facing the object side; the third lens is a double convex lens with a positive focal length; the fourth lens is a double convex lens with a positive focal length; the fifth lens is a double concave lens with a negative focal length; the sixth lens is a meniscus lens with a positive focal length, with a concave surface facing the object side; the seventh lens is a double concave lens with a negative focal length; the eighth lens is a double convex lens with a positive focal length; the ninth lens is a double convex lens with a positive focal length; the tenth lens is a double concave lens with a negative focal length; the third lens and the sixth lens are glass aspherical lenses, and the remaining lenses are glass spherical lenses; the focal length of the third lens is f3, the focal length of the sixth lens is f6, the overall focal length of the lens is f, and the relationship is satisfied:

[0005] 1.08<(f3 / f)<1.5(1)

[0006] 4.5<(f6 / f)<6.5(2).

[0007] Preferably, the material refractive index of the third lens is ND3, and the material refractive index of the sixth lens is ND6, which satisfies the relationship: ND3=ND6>1.85.

[0008] Preferably, the first lens and the second lens are a group of doublet lenses, the fourth lens and the fifth lens are a group of doublet lenses, the seventh lens and the eighth lens are a group of doublet lenses, and the ninth lens and the tenth lens are a group of doublet lenses.

[0009] Preferably, in the double-cemented lens, the refractive index of the lens with a positive focal length is greater than 1.88, and the dispersion coefficient of the lens with a negative focal length is less than 35.

[0010] Preferably, an aperture device is provided between the fifth lens and the sixth lens.

[0011] The present invention uses glass aspheric surfaces and double-cemented lens groups in a reasonable manner, and limits the structure, focal length, and arrangement order of each lens, thereby effectively reducing the total length of the lens and improving the camera effect. This patent has the characteristics of ultra-high resolution, large aperture, and ultra-thinness. Compared with the prior art, the present invention has the following advantages:

[0012] 1. The length is ultra-thin, controlled below 70mm.

[0013] 2. The lens diameter is small and controlled below 30mm.

[0014] 3. Small number of lenses. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic diagram of a lens according to an embodiment of the present invention;

[0016] Figure 2 Analytical diagram of an embodiment of the present invention;

[0017] Figure 3 is a distortion diagram of an embodiment of the present invention;

[0018] Figure 4 2 is a relative illumination diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0019] like Figure 1 As shown, Figure 1As shown, a specific embodiment of the present invention provides an optical lens, which includes: a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7, an eighth lens 8, a ninth lens 9, and a tenth lens 10 in order from the object side to the image side along the optical axis. The first lens 1 is a double concave lens with a negative focal length, the second lens 2 is a meniscus lens with a positive focal length, and the convex surface faces the object, the third lens 3 is a double convex lens with a positive focal length, the fourth lens 4 is a double convex lens with a positive focal length, the fifth lens 5 is a double concave lens with a negative focal length, the sixth lens 6 is a meniscus lens with a positive focal length and a concave surface facing the object side, the seventh lens 7 is a double concave lens with a negative focal length, the eighth lens 8 is a double convex lens with a positive focal length, the ninth lens 9 is a double convex lens with a positive focal length, and the tenth lens 10 is a double concave lens with a negative focal length. Among them, the third lens and the sixth lens are glass aspherical lenses, and the other lenses are glass spherical lenses. The third lens and the sixth lens are glass aspheric lenses, and the other lenses are glass spherical lenses. By using glass aspheric lenses and double cemented lens groups reasonably, the total length of the lens is effectively reduced and the camera effect is improved. This patent has the characteristics of ultra-high resolution, large aperture, and ultra-thinness to overcome the shortcomings of the prior art.

[0020] By adopting the structural shape of the optical lens system provided by the present invention, the parameters such as the Abbe coefficient of the optical glass material are well matched with the imaging conditions, so that the spherical aberration, coma, astigmatism, field curvature, magnification chromatic aberration and position chromatic aberration of the lens system are well corrected, meeting the use requirements of SLR cameras and having a small size for portability.

[0021] In a specific implementation, in the above optical lens provided in the embodiment of the present invention, Figure 1 As shown, the first lens and the second lens are a group of double-cemented lenses A, the fourth lens and the fifth lens are a group of double-cemented lenses B, the seventh lens and the eighth lens are a group of double-cemented lenses C, the ninth lens and the tenth lens are a group of double-cemented lenses D, and an aperture device ST is provided between the fifth lens and the sixth lens. Since a lens with a positive focal power has negative chromatic aberration, and a lens with a negative focal power has positive chromatic aberration, a lens with a positive focal power and a lens with a negative focal power are seamlessly bonded to form a bonded lens group to achieve mutual compensation of chromatic aberration and eliminate chromatic aberration. The fixed-focus lens provided in an embodiment of the present invention contains four groups of bonded lenses, each of which includes a lens with a positive focal length and a lens with a negative focal length, to achieve mutual compensation of chromatic aberration, eliminate chromatic aberration, optimize imaging clarity, improve the image quality of the optical system, and increase resolution.

[0022] Furthermore, in the above optical lens provided in the embodiment of the present invention, Figure 1As shown, the refractive index of the positive lens, ND2, ND4, ND8, and ND9 are all greater than 1.88. The larger the refractive index of the lens, the greater the light deflection angle and the shorter the optical path. Using high refractive index materials for the positive lens can effectively reduce the total length of the system.

[0023] Furthermore, in the above-mentioned optical lens provided in an embodiment of the present invention, the focal length of the third lens is f3, the focal length of the sixth lens is f6, and the overall focal length of the lens is f, satisfying the relationship: 1.08<(f3 / f)<1.5(1); 4.5<(f6 / f)<6.5(2).

[0024] When the value of |f3 / f| exceeds the upper limit of 1.5, f3 becomes relatively large, that is, the optical power becomes relatively small, resulting in insufficient optical back focus and difficulty in arranging parts such as the automatic red filter switching device in the structural space; when the value of |f3 / f| is lower than the lower limit of 6.75, f3 becomes relatively small, that is, the optical power becomes relatively large, which will cause an increase in high-order aberrations. Therefore, the optical lens in the embodiment of the present invention can achieve better imaging quality and a reasonable structural space form when the condition 1.08<(f3 / f)<1.5 is met.

[0025] Furthermore, when the value of |f6 / f| exceeds the upper limit of 6.5, f6 becomes relatively large, that is, the focal length becomes relatively small, resulting in insufficient optical back focus and difficulty in arranging parts such as the automatic red filter switching device in the structural space; when the value of |f6 / f| is lower than the lower limit of 4.5, f6 becomes relatively small, that is, the focal length becomes relatively large, which will cause an increase in high-order aberrations, thereby requiring a large number of lenses, making it difficult to achieve an optical system with good imaging performance with a small number of lens structures. Therefore, the optical lens in the embodiment of the present invention can achieve better imaging quality when the condition 4.5<(f6 / f)<6.5 is met.

[0026] The following content will cite an embodiment of the optical lens of the present invention, with a total focal length of f=35.4mm, FNO=1.2, a field of view angle FOV=64°, a lens distortion=-2%, and a total length of 65mm for an ultra-thin digital SLR camera with a large aperture full-frame lens. The parameters of the lens group are listed in Table 1:

[0027] Table 1

[0028]

[0029]

[0030] In Table 1, surface is the surface number, Thickness is the thickness parameter, GlassName is the glass material, Index is the refractive index, ABB is the Abbe constant, Radius is the curvature radius, and EFL-E are the focal lengths f1 to f10 of the first lens to the tenth lens, respectively.

[0031] In Table 1, mirror numbers 1, 2, and 3 represent the three mirrors of the cemented lens group A along the light incident direction, wherein 2 represents the cemented surface of lens 1 and lens 2, mirror numbers 4 and 5 represent the two mirrors of lens 3 along the light incident direction, mirror number 4 represents the mirror of lens 3 facing the object side, and mirror number 5 represents the mirror of lens 3 facing the image side, mirror numbers 6, 7, and 8 represent the three mirrors of the cemented lens group B along the light incident direction, wherein 7 represents the cemented surface of lens 4 and lens 5,

[0032] Mirror numbers 9 and 10 represent the two mirrors of lens 6 along the incident direction of light, mirror number 9 represents the mirror of lens 6 facing the object side, mirror number 10 represents the mirror of lens 6 facing the image side, mirror numbers 11, 12, and 13 represent the three mirrors of cemented lens group C along the incident direction of light, among which 12 represents the cemented surface of lens 7 and lens 8, mirror numbers 14, 15, and 16 represent the three mirrors of cemented lens group D along the incident direction of light, among which 15 represents the cemented surface of lens 9 and lens 10,

[0033] In the embodiment of the present invention, f3 / f=45.928366 / 35.4=1.297, which satisfies 1.08<(f3 / f)<1.5. In the embodiment of the present invention, f6 / f=196.0935 / 35.4=5.54, which satisfies 4.5<(f6 / f)<6.5.

[0034] In the embodiment of the present invention, the third lens and the sixth lens are glass aspheric lenses, both made of M-TAFD307, with a material refractive index of ND3=ND6=1.882023, and both adopt high refractive material, satisfying the relationship: ND3=ND6>1.85.

[0035] In the embodiment of the present invention, ND2=1.953747, ND4=1.883, ND8=1.883, ND9=1.883, all are greater than 1.88, VD1=33.842283, VD5=31.160527, VD7=28.315013, VD10=33.842283, all are less than 35, and all meet the requirements.

[0036] In the embodiment of the present invention, the third lens and the sixth lens are glass aspheric lenses, and the aspheric surface related values ​​are listed in Table 2:

[0037] Table 2

[0038] SURFACE:4 SURFACE:5 K＝-4.427041343 K＝171119.702277300 E4＝-0.000004440658146468 E4＝-0.000009357608530060 E6＝-0.000000052134992337 E6＝-0.000000046762800032 E8＝-0.000000000023607920 E8＝-0.000000000078832522 E10＝-0.000000000000641100 E10＝-0.000000000000174200 R1＝40.238326956 R2＝5620.021630922 SURFACE:9 SURFACE:10 K＝25.615371731 K＝12.490803098 E4＝-0.000033915993811870 E4＝-0.000002343772665113 E6＝-0.000000235083498050 E6＝-0.000000159653338750 E8＝0.000000000129358261 E8＝0.000000000491574246 E10＝0.000000000001967100 E10＝0.000000000001638900 R1＝-75.714027656 R2＝-53.301652968

[0039] In the embodiment of the present invention, it can be calculated from Table 1 that the field angle 2w of the optical lens is 64 degrees and the relative aperture is 1.2. In the embodiment of the present invention, the total length of the lens is 65 mm and the structure is relatively compact. Figure 2 The modulation transfer function (MTF) curve of the visible light band represents the comprehensive resolution ability of the optical system. The horizontal axis of the figure represents the spatial frequency, and the unit is cycles per millimeter (cycles / mm). The chip pixel of the SLR camera is relatively large, and the evaluation is 40lp / mm. The vertical axis represents the value of the modulation transfer function (MTF). The value of MTF is used to evaluate the imaging quality of the lens, and the value range is 0-1. It is particularly pointed out that the optical transfer function is used to evaluate the imaging quality of an optical system. The more accurate, intuitive and common way, the higher and smoother the curve is, the better the imaging quality of the system is, and the stronger the ability to restore the real image is; from Figure 2 It can be seen that when the spatial frequency of the visible light band is 40lp / mm, the MTF of the main field of view is>0.2. The super-large aperture full-frame lens of the digital SLR camera has the advantages of ultra-thin, super-large aperture, correction of various aberrations, compact structure, good imaging effect and high cost performance.

[0040] Figure 2 is the distortion diagram corresponding to the visible light part of the lens system. The closer the curve is to the y-axis, the smaller the distortion rate. Figure 3 As shown, the optical distortion rate is controlled within the range of -2% to 0%, and the image has no obvious deformation. Figure 4 As shown, the SLR camera has larger pixels, better sensitivity, and a relative illumination greater than 20%, which meets the usage requirements.

Claims

1. An ultra-thin lens for a SLR camera, characterized in that: The invention is composed of ten lenses, including 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 arranged in sequence from the object side to the image side; the first lens is a double concave lens with a negative focal length; the second lens is a meniscus lens with a positive focal length, with the convex surface facing the object side; the third lens is a double convex lens with a positive focal length; the fourth lens is a double convex lens with a positive focal length; the fifth lens is a double concave lens with a negative focal length; the sixth lens is a meniscus lens with a positive focal length, with a concave surface facing the object side; the seventh lens is a double concave lens with a negative focal length; the eighth lens is a double convex lens with a positive focal length; the ninth lens is a double convex lens with a positive focal length; the tenth lens is a double concave lens with a negative focal length; the third lens and the sixth lens are glass aspherical lenses, and the remaining lenses are glass spherical lenses; the focal length of the third lens is f3, the focal length of the sixth lens is f6, the overall focal length of the lens is f, and the relationship is satisfied: 1.08<(f3 / f)<1.5 (1) 4.5<(f6 / f)<6.5 (2).

2. The ultra-thin lens for a SLR camera according to claim 1, characterized in that: The material refractive index of the third lens is ND3, and the material refractive index of the sixth lens is ND6, which satisfies the relationship: ND3=ND6>1.

85.

3. The ultra-thin lens for a SLR camera according to claim 1, characterized in that: The first lens and the second lens are a group of doublet lenses, the fourth lens and the fifth lens are a group of doublet lenses, the seventh lens and the eighth lens are a group of doublet lenses, and the ninth lens and the tenth lens are a group of doublet lenses.

4. The ultra-thin lens for a SLR camera according to claim 3, characterized in that: In the double-cemented lens, the refractive index of the lens with a positive focal length is greater than 1.88, and the dispersion coefficient of the lens with a negative focal length is less than 35.

5. The ultra-thin lens for a SLR camera according to claim 1, characterized in that: An aperture device is provided between the fifth lens and the sixth lens.

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