CN210376840U - Low-distortion rearview optical system - Google Patents
Low-distortion rearview optical system Download PDFInfo
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- CN210376840U CN210376840U CN201921214393.0U CN201921214393U CN210376840U CN 210376840 U CN210376840 U CN 210376840U CN 201921214393 U CN201921214393 U CN 201921214393U CN 210376840 U CN210376840 U CN 210376840U
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Abstract
The utility model relates to a low distortion rear view optical system, include along the light incident light path from preceding first lens, second lens, third lens, diaphragm, fourth lens and the fifth lens that sets up at interval backward in proper order, first lens and second lens are meniscus negative lens, the third lens is biconvex positive lens, and first lens, second lens and third lens constitute the front group camera lens that the light angle is negative; the fourth lens is a biconvex positive lens, the fifth lens is a meniscus negative lens, and the fourth lens and the fifth lens are tightly connected to form a cemented lens group and form a rear group lens with a positive optical angle; the concave surfaces of the first lens, the second lens and the fifth lens face the diaphragm. The utility model has the advantages of simple and reasonable structure, can have the low distortion characteristic when providing great angle of vision to adopt more aspheric lens, reach the purpose that improves like quality and reduce cost.
Description
The technical field is as follows:
the utility model relates to a low distortion rear view optical system.
Background art:
the wide-angle fixed-focus lens is widely applied to vehicle-mounted monitoring systems, particularly vehicle-mounted rear-view systems, and along with the development of the automobile industry, higher requirements are put forward on the performance of the wide-angle lens. The common vehicle-mounted rear wide-angle lens on the market mainly faces the following two problems:
firstly, a common rearview mirror head generally adopts a 5-6-piece full-glass lens structure, the size of the lens is large, the weight is heavy, the requirement of miniaturization cannot be met, and the manufacturing cost of the full-glass design is high in manufacturing cost;
secondly, the field angle of a common rearview mirror is large, the corresponding edge light flux is small, and the edge imaging is not clear enough; the total imaging distortion is large, and the imaging quality is insufficient.
The utility model has the following contents:
an object of the utility model is to above weak point, provide a low distortion back vision optical system, structural design is reasonable, can have the low distortion characteristic when providing great angle of vision, reaches the purpose that improves image quality and reduce cost.
In order to realize the purpose, the utility model discloses a technical scheme is: a low-distortion rearview optical system comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged at intervals from front to back along a light incident light path, wherein the first lens and the second lens are both meniscus negative lenses, the third lens is a double convex positive lens, and the first lens, the second lens and the third lens form a front group lens with a negative light angle; the fourth lens is a biconvex positive lens, the fifth lens is a meniscus negative lens, and the fourth lens and the fifth lens are tightly connected to form a cemented lens group and form a rear group lens with a positive optical angle.
Further, the air space between the first lens and the second lens is 1.4mm, the air space between the second lens and the third lens is 1.0mm, and the air space between the third lens and the fourth lens is 0.2 mm.
Further, the focal length of an optical system formed by the front group lens and the rear group lens is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are respectively f1、f2、f3、f4、f5Wherein f is1、f2、f3And f satisfy the following ratio: -6 < f1/f＜-5，-3＜f2/f＜-2，3＜f3/f＜4。
Further, the focal length f of the fourth lens and the focal length f of the fifth lens are4And f5The following proportions are satisfied: 1.5 < f4/f5＜2。
Further, the first lens satisfies the relation: n is a radical ofd≥1.7，VdNot less than 45; the second lens satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the third lens satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25; the fourth lens satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the fifth lens satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25, wherein N isdIs refractive index, VdAbbe constant.
Furthermore, the first lens is a spherical lens and is made of a glass material; the second lens element, the third lens element, the fourth lens element and the fifth lens element are aspheric lens elements and are made of plastic material.
Further, a diaphragm is arranged between the third lens and the fourth lens, and concave surfaces of the first lens, the second lens and the fifth lens face the diaphragm.
Compared with the prior art, the utility model discloses following effect has:
(1) by introducing a plurality of aspheric lenses and a group of aspheric cemented lens groups, the focal power of each lens surface is reasonably distributed, and the high-level aberration and chromatic aberration of the system are effectively corrected;
(2) the reasonable surface design is adopted, so that the aspheric lens can effectively control the distortion of the whole optical system;
(3) by adopting the design structure of 1G4P, compared with the full-glass design, the structure is simpler, the size and the quality are smaller, and the addition of the aspheric cemented lens group reduces the assembly sensitivity, improves the yield, reduces the cost and is beneficial to large-scale production; in addition, the imaging quality is better, and the level of megapixel shooting is achieved.
Description of the drawings:
fig. 1 is a schematic structural diagram of an optical system according to an embodiment of the present invention;
fig. 2 is a graph of visible light MTF of an embodiment of the present invention;
fig. 3 is a distortion plot of an embodiment of the present invention;
fig. 4 is a defocus graph according to an embodiment of the present invention.
In the figure:
a1 — first lens; a2 — second lens; a3 — third lens; b1-fourth lens; b2-fifth lens; c-diaphragm; a D-filter.
The specific implementation mode is as follows:
the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in fig. 1, the present invention relates to a low distortion rear-view optical system, which comprises a first lens a1, a second lens a2, a third lens A3, a diaphragm C, a fourth lens B1 and a fifth lens B2, which are sequentially disposed along a light incident path from front to back at intervals, wherein the first lens a1 and the second lens a2 are meniscus negative lenses, the third lens A3 is a biconvex positive lens, and the first lens a1, the second lens a2 and the third lens A3 form a front group lens with a negative light angle; the fourth lens element B1 is a biconvex positive lens element, the fifth lens element B2 is a negative meniscus lens element, and the fourth lens element B1 and the fifth lens element B2 are tightly connected to form a cemented lens group and a rear lens group with a positive optical angle; the concave surfaces of the first lens, the second lens and the fifth lens face the diaphragm.
In this embodiment, the air space between the first lens a1 and the second lens a2 is 1.41mm, the air space between the second lens a2 and the third lens A3 is 0.97mm, and the air space between the third lens A3 and the fourth lens B1 is 0.17 mm.
In this embodiment, a focal length of an optical system formed by the front group lens and the rear group lens is f, and focal lengths of the first lens a2, the second lens a2, the third lens A3, the fourth lens B1 and the fifth lens B2 are respectively f1、f2、f3、f4、f5Wherein f is1、f2、f3And f satisfy the following ratio: -6 < f1/f＜-5，-3＜f2/f＜-2，3＜f3/f＜4。
In this embodiment, the focal lengths f of the fourth lens B1 and the fifth lens B24And f5The following proportions are satisfied: 1.5 < f4/f5Is less than 2. Through right the utility model discloses the optical system's that forms focal power carries out rational distribution according to above proportion, and each lens is for system's focus f certain proportion, makes the utility model discloses the optical system who forms obtains reasonable correction and balance at 420 ~ 700 nm's wavelength range's aberration.
In this embodiment, the first lens a1 satisfies the following relation: n is a radical ofd≥1.7，VdNot less than 45; the second lens A2 satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the third lens A3 satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25; the fourth lens B1 satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the fifth lens B2 satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25, wherein N isdIs refractive index, VdAbbe constant.
In this embodiment, the first lens a1 is a spherical lens and is made of glass; the second lens a2, the third lens A3, the fourth lens B1 and the fifth lens B2 are aspheric lenses and are made of plastic materials.
In this embodiment, a filter D is disposed on a rear side of the fifth lens.
As shown in table 1, the curvature radius R, the thickness d, and the refractive index N of each lens of the optical lens in this embodiment aredAnd Abbe number Vd。
Table 1:
in the embodiment, five lenses are taken as an example, and by reasonably distributing the focal power, the surface type, the central thickness of each lens, the on-axis distance between each lens and the like, the field angle of the lens is effectively enlarged, the total length of the lens is shortened, and the small distortion and the high illumination of the lens are ensured; meanwhile, various aberrations are corrected, and the resolution and the imaging quality of the lens are improved. Each aspherical surface type Z is defined by the following formula:
wherein Z is the distance rise from the vertex of the aspheric surface when the aspheric surface is at the position with the height of h along the optical axis direction; c is the paraxial curvature of the aspheric surface, c being 1/R (i.e., paraxial curvature c is the inverse of radius of curvature R in table 1 above); k is a conic constant; A. b, C, D, E are all high order term coefficients. Table 2 shows a conic constant k and a high-order term coefficient A, B, C, D, E that can be used for each aspherical lens surface in the present embodiment.
Table 2:
in this embodiment, the technical indexes of the optical system are as follows:
(1) focal length: EFFL 1.24 mm; (2) the diaphragm F is 2.0; (3) the field angle: 2w is more than or equal to 140 degrees; (4) optical distortion: less than-35 percent; (5) the diameter of the imaging circle is larger than phi 4.8; (6) the working wave band is as follows: 420-700 nm; (7) the total optical length TTL is less than or equal to 12.9mm, and the optical back intercept BFL is more than or equal to 2.6 mm; (8) the lens is suitable for a megapixel CCD or CMOS camera.
In the embodiment of the present invention, the first glass a1 has a larger refractive index and focal power, which ensures that the system has a larger field of view; the second glass A2 is selected to be in a proper surface shape, so that the distortion of an optical system is effectively corrected; the negative focal power of the front group lens corrects the positive focal power aberration of the rear group lens, the four aspheric lenses correct all high-level aberrations and spherical aberration, the refractive index and the focal power of the whole lens are distributed in an approximate proportion, and the balance of the incident angles of the lenses of the front group lens and the lenses of the rear group lens is guaranteed; by introducing a group of cemented aspheric lenses, chromatic aberration and astigmatism of an imaging system are corrected, meanwhile, the sensitivity of the lens is reduced, and the possibility of production is improved.
Through the optical system formed by the lenses, the total length of the optical path is short, so that the lens is small in size and large in back focus, and can be matched with cameras with various interfaces for use; the second lens A2, the third lens A3, the fourth lens B1 and the fifth lens B2 are plastic aspheric lenses, so that the image quality is good and the cost is low; the front group of lenses has negative focal power, the rear group of lenses has positive focal power, the angle of a view field reaches 140 degrees, the distortion is low, and the imaging quality is excellent.
As can be seen from FIG. 2, the MTF of the optical system in the visible light band is well-behaved, the MTF value is greater than 0.5 at the spatial frequency of 120pl/mm, and the MTF value is greater than 0.6 at the spatial frequency of 80pl/mm, so that the resolution requirement of million high definition can be achieved. As can be seen from fig. 3 and 4, when the FOV of the lens is 140 °, the distortion rate of the lens is controlled within-35%; when the spatial frequency is 80pl/mm, the defocus of the lens is controlled in the range of-0.006 mm to 0.006mm, and the MTF value is greater than 0.7 at the defocus position of 0, so that it can be seen that the low distortion rear view optical system taught in this embodiment has low lens distortion rate and clear image plane without distortion in the case of having a large field angle, and simultaneously has small lens defocus and high lens resolution.
The above is only the preferred embodiment of the present invention, and all the equivalent changes and modifications made according to the claims of the present invention should be covered by the present invention.
Claims (7)
1. A low distortion rearview optical system, comprising: the optical lens comprises a first lens, a second lens, a third lens, a fourth lens and a fifth lens which are sequentially arranged at intervals from front to back along a light incident light path, wherein the first lens and the second lens are meniscus negative lenses, the third lens is a double-convex positive lens, and the first lens, the second lens and the third lens form a front group lens with a negative optical angle; the fourth lens is a biconvex positive lens, the fifth lens is a meniscus negative lens, and the fourth lens and the fifth lens are tightly connected to form a cemented lens group and form a rear group lens with a positive optical angle.
2. A low distortion rearview optical system as claimed in claim 1, wherein: the air space between the first lens and the second lens is 1.4mm, the air space between the second lens and the third lens is 1.0mm, and the air space between the third lens and the fourth lens is 0.2 mm.
3. A low distortion rearview optical system as claimed in claim 1, wherein: the focal length of an optical system formed by the front group lens and the rear group lens is f, and the focal lengths of the first lens, the second lens, the third lens, the fourth lens and the fifth lens are respectively f1、f2、f3、f4、f5Wherein f is1、f2、f3And f satisfy the following ratio: -6 < f1/f＜-5，-3＜f2/f＜-2，3＜f3/f＜4。
4. A low distortion rearview optical system as claimed in claim 3, wherein: focal length f of the fourth lens and the fifth lens4And f5The following proportions are satisfied: 1.5 < f4/f5＜2。
5. A low distortion rearview optical system as claimed in claim 1, wherein: the first lens satisfies the relation: n is a radical ofd≥1.7，VdNot less than 45; the second lens satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the third lens satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25; the fourth lens satisfies the relation: n is a radical ofd≥1.5，VdNot less than 50; the fifth lens satisfies the relation: n is a radical ofd≥1.6，VdLess than or equal to 25, wherein N isdIs refractive index, VdAbbe constant.
6. A low distortion rearview optical system as claimed in claim 1, wherein: the first lens is a spherical lens and is made of a glass material; the second lens element, the third lens element, the fourth lens element and the fifth lens element are aspheric lens elements and are made of plastic material.
7. A low distortion rearview optical system as claimed in claim 1, wherein: and a diaphragm is arranged between the third lens and the fourth lens, and the concave surfaces of the first lens, the second lens and the fifth lens face the diaphragm.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921214393.0U CN210376840U (en) | 2019-07-30 | 2019-07-30 | Low-distortion rearview optical system |
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| CN201921214393.0U CN210376840U (en) | 2019-07-30 | 2019-07-30 | Low-distortion rearview optical system |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110456477A (en) * | 2019-07-30 | 2019-11-15 | 福建福光天瞳光学有限公司 | The low distortion backsight optical system of one kind and imaging method |
| CN112612114A (en) * | 2020-12-29 | 2021-04-06 | 福建福光天瞳光学有限公司 | Low-distortion six-lens type optical lens and imaging method thereof |
-
2019
- 2019-07-30 CN CN201921214393.0U patent/CN210376840U/en active Active
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110456477A (en) * | 2019-07-30 | 2019-11-15 | 福建福光天瞳光学有限公司 | The low distortion backsight optical system of one kind and imaging method |
| CN110456477B (en) * | 2019-07-30 | 2024-07-05 | 福建福光天瞳光学有限公司 | Low-distortion rearview optical system and imaging method |
| CN112612114A (en) * | 2020-12-29 | 2021-04-06 | 福建福光天瞳光学有限公司 | Low-distortion six-lens type optical lens and imaging method thereof |
| CN112612114B (en) * | 2020-12-29 | 2023-09-19 | 福建福光天瞳光学有限公司 | Low-distortion six-piece optical lens and imaging method thereof |
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