CN111736325A - Coaxial telecentric lens - Google Patents
Coaxial telecentric lens Download PDFInfo
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- CN111736325A CN111736325A CN202010742390.5A CN202010742390A CN111736325A CN 111736325 A CN111736325 A CN 111736325A CN 202010742390 A CN202010742390 A CN 202010742390A CN 111736325 A CN111736325 A CN 111736325A
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- 238000003384 imaging method Methods 0.000 claims abstract description 8
- 239000011521 glass Substances 0.000 claims description 18
- 230000003287 optical effect Effects 0.000 claims description 9
- 230000000694 effects Effects 0.000 abstract description 3
- 230000004075 alteration Effects 0.000 description 10
- 238000010586 diagram Methods 0.000 description 4
- 210000001747 pupil Anatomy 0.000 description 4
- 201000009310 astigmatism Diseases 0.000 description 3
- 238000001514 detection method Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B13/00—Optical objectives specially designed for the purposes specified below
- G02B13/22—Telecentric objectives or lens systems
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Abstract
The invention discloses a coaxial telecentric lens, which comprises a first lens with positive focal power, wherein the object side surface is a convex surface and comprises a first spherical surface and a second spherical surface; the second lens with positive focal power, the object side surface of which is convex and comprises a third spherical surface and a fourth spherical surface; the third lens with negative focal power, the object side surface of which is concave, comprises a fifth spherical surface and a sixth spherical surface; the fourth lens with positive focal power has a convex object-side surface and comprises a seventh spherical surface and an eighth spherical surface; the fifth lens is provided with positive focal power, the object side surface is a convex surface, and the fifth lens comprises a ninth spherical surface and a tenth spherical surface; the sixth lens with negative focal power, the object side surface of which is concave, comprises an eleventh spherical surface and a twelfth spherical surface; the object side surface of the seventh lens with positive focal power is a convex surface and comprises a thirteenth spherical surface and a fourteenth spherical surface, the second lens, the third lens and the fourth lens form a three-cemented lens, and the fifth lens and the sixth lens form a double-cemented lens. The invention has good imaging effect, small number of lenses and apochromatism.
Description
Technical Field
The invention relates to the technical field of industrial lens application, in particular to a coaxial telecentric lens.
Background
At present, the industrial detection requirement is higher and higher, the application of the adopted color industrial cameras is wider and wider, the detected object needs good color reduction degree, the accurate result can be obtained by combining the algorithm, and certain WRGB (white light and red, green and blue) special use requirements, namely confocal special use requirements of white light and red, green and blue, are required, so that strict requirements are provided for the industrial imaging lens, and the imaging lens only applied to the black and white camera in the past cannot be well applied.
An effective solution to the problems in the related art has not been proposed yet.
Disclosure of Invention
The invention aims to provide an object space telecentric lens which has the advantages of correcting various aberrations, good imaging effect, small lens number, high cost performance and realization of apochromatic function.
In order to achieve the purpose, the invention provides the following technical scheme: a coaxial telecentric lens comprises the following components in sequence from an object plane to an image plane:
the lens comprises a first lens with positive focal power, a second lens and a third lens, wherein the object side surface of the first lens is a convex surface and comprises a first spherical surface (convex surface) and a second spherical surface (convex surface);
the object side surface of the second lens is a convex surface and comprises a third spherical surface (convex surface) and a fourth spherical surface (convex surface);
a third lens having negative refractive power, the object side surface of which is concave, and which includes a fifth spherical surface (concave surface) and a sixth spherical surface (concave surface);
a fourth lens with positive focal power, the object side surface of which is convex, and which comprises a seventh spherical surface (convex surface) and an eighth spherical surface (concave surface);
a fifth lens with positive optical power, which has a convex object-side surface and includes a ninth spherical surface (convex surface) and a tenth spherical surface (convex surface or plane surface);
a sixth lens having a negative refractive power, an object side surface of which is concave, and which includes an eleventh spherical surface (concave surface) and a twelfth spherical surface (concave surface);
a seventh lens having positive optical power, the object-side surface of which is convex, comprising a thirteenth spherical surface (convex surface) and a fourteenth spherical surface (convex surface);
the fourth spherical surface of the second lens is cemented with the fifth spherical surface of the third lens, and the sixth spherical surface of the third lens is cemented with the seventh spherical surface of the fourth lens, namely the second lens, the third lens and the fourth lens form a triple cemented lens;
the tenth spherical surface of the fifth lens and the eleventh spherical surface of the sixth lens are cemented, that is, the fifth lens and the sixth lens form a double cemented lens.
Furthermore, a light splitting prism is arranged in the coaxial telecentric lens, is close to the diaphragm and is positioned on the object side.
Furthermore, at least one of the first lens and the second lens satisfies 1.45< n <1.6 and 62< lambda <95, wherein n is the refractive index of the lens glass, and lambda is the Abbe number of the lens glass.
Further, the positive lens closest to the image side of the diaphragm in the coaxial telecentric lens meets the conditions that 1.45< n <1.6 and 62< lambda <95, wherein n is the refractive index of glass and lambda is the Abbe number of the glass.
Further, the coaxial telecentric lens close to the positive focal lens on the side of the diaphragm object satisfies the following conditions: 1.75< n <1.95, 15< λ <35, where n is the refractive index of the glass and λ is the abbe number of the glass.
Further, the coaxial telecentric lens is a conjugate imaging system and satisfies 0.8< L2/L1<2, wherein L1 is the distance from the object plane to the system diaphragm, and L2 is the distance from the diaphragm to the image plane.
Further, the coaxial telecentric lens meets the requirement that 1.7< f1/H <2.8, wherein f1 is the focal distance of the first lens, and H is the image surface size.
Further, the coaxial telecentric lens meets the requirement that 0.5< f1/f0<1, wherein f1 is the focal distance of the first lens, and f0 is the combined focal length of all the lenses in front of the front group, namely the diaphragm.
Compared with the prior art, the invention has the following beneficial effects: the coaxial telecentric lens provided by the invention can correct various aberrations, has good imaging effect, small lens number and high cost performance, and achieves the purpose of apochromatism.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a coaxial telecentric lens according to an embodiment of the invention.
Fig. 2 is a graph of on-axis differential curves according to an embodiment of the present invention.
Fig. 3 is an astigmatism graph of a coaxial telecentric lens according to an embodiment of the invention.
Fig. 4 is a distortion plot according to an embodiment of the present invention.
Fig. 5 is a graph of chromatic aberration of magnification according to an embodiment of the present invention.
Fig. 6 is a graph of MTF VS Field according to an embodiment of the invention.
Fig. 7 is a parameter diagram of a coaxial telecentric lens system according to an embodiment of the invention.
Detailed Description
The invention is further described with reference to the following drawings and detailed description:
referring to fig. 1-7, a coaxial telecentric lens according to an embodiment of the invention sequentially includes, from an object plane 0 to an image plane 10:
the first lens 1 with positive focal power has a convex object-side surface and comprises a first spherical convex surface and a second spherical convex surface;
the object side surface of the second lens 2 with positive focal power is a convex surface and comprises a third spherical convex surface and a fourth spherical convex surface;
the third lens 3 with negative focal power has a concave object-side surface and comprises a fifth spherical concave surface and a sixth spherical concave surface;
the fourth lens 4 with positive focal power has a convex object-side surface and comprises a seventh spherical convex surface and an eighth spherical concave surface;
a fifth lens 5 with positive focal power, the object side surface of which is convex, and which comprises a ninth spherical convex surface and a tenth spherical convex surface or plane;
a sixth lens 6 having a negative refractive power, the object side surface of which is concave, and which includes an eleventh spherical surface (concave surface) and a twelfth spherical surface (concave surface);
a seventh lens element 7 with positive optical power, which has a convex object-side surface and includes a thirteenth convex spherical surface and a fourteenth convex spherical surface;
the system adopts a piece of tri-cemented lens, so that the overall length of the system is effectively reduced, and the axial chromatic aberration of the system is well inhibited, so as to achieve the aim of apochromatic aberration;
the tenth spherical surface of the fifth lens 5 and the eleventh spherical surface of the sixth lens 6 are cemented, that is, the fifth lens 5 and the sixth lens 6 constitute a double-cemented lens.
According to the scheme of the invention, the coaxial telecentric lens is internally provided with the beam splitter prism 8, the beam splitter prism 8 is close to the diaphragm 9 and is positioned on the object side, and the position is favorable for using a smaller beam splitter prism 8, so that the cost is saved, the length and the volume of the system are reduced, and meanwhile, the phenomenon that redundant stray light irradiated on the beam splitter prism 8 by a light source directly irradiates on the image surface 10 can be reduced.
Through the scheme of the invention, at least one of the first lens 1 and the second lens 2 satisfies 1.45< n <1.6 and 62< lambda <95, wherein n is the refractive index of lens glass, and lambda is the Abbe number of the lens glass, so that chromatic aberration can be effectively reduced.
By the scheme, the positive lens closest to the image side of the diaphragm 9 in the coaxial telecentric lens meets the requirements that n is more than 1.45 and less than 1.6, and λ is more than 62 and less than 95, wherein n is the refractive index of glass, and λ is the Abbe number of the glass, so that chromatic aberration can be effectively reduced.
Through the scheme of the invention, in order to effectively reduce the volume, the system introduces a high-refractive-index lens, and the coaxial telecentric lens close to the positive focal lens on the object side of the diaphragm 9 meets the following requirements: 1.75< n <1.95, 15< λ <35, where n is the refractive index of the glass and λ is the abbe number of the glass.
Through the scheme of the invention, the coaxial telecentric lens is a conjugate imaging system and meets the requirement that 0.8< L2/L1<2, wherein L1 is the distance from an object plane to a system diaphragm 9, and L2 is the distance from the diaphragm 9 to an image plane 10.
By the scheme of the invention, the coaxial telecentric lens meets the condition that 1.7< f1/H <2.8, wherein f1 is the focal distance of the first lens, and H is the size of an image plane 10.
With the above scheme of the present invention, the coaxial telecentric lens satisfies 0.5< f1/f0<1, where f1 is the focal distance of the first lens, and f0 is the combined focal length of all the lenses in front of the front group, i.e. the diaphragm 9.
Fig. 2 is an on-axis chromatic aberration diagram of the telecentric lens according to the embodiment of the invention, wherein the on-axis chromatic aberration diagram shows the degree of different bands deviating from the ideal image plane position in different pupil bands. The horizontal axis represents offset and the vertical axis represents normalized pupil band. Mainly looking at the smallest offset of all wavelengths near the 0.707 pupil zone, as in this figure, the transverse axial distance of the wavelengths 435.8nm and 656.3nm, which are farthest from the 0.8 pupil zone, is about 0.02mm, while for a conventional common achromatic similar specification lens, this value is often greater than 0.1mm, so that the optical performance of the present invention is more advantageous.
FIG. 3 is an astigmatism graph of a telecentric lens according to an embodiment of the invention. Astigmatism represents the degree of deviation of the image field from the ideal image field in the design meridional and sagittal directions. The horizontal axis represents the offset amount, and the vertical axis represents the half-image height. If the image field deviation of the image system is within 0.2 in the whole field of view, the maximum deviation of the meridional and sagittal curves is about 0.1.
FIG. 4 is a distortion plot of a telecentric lens according to an embodiment of the invention. The distortion map represents the difference between the actual image height and the ideal image height. The horizontal axis represents the distortion percentage and the vertical axis represents the half-image height. It can be seen that the distortion of the system is within 0.02%, and the system is almost suitable for all high-precision industrial detection requirements.
Fig. 5 is a graph of magnification chromatic aberration of the telecentric lens according to the embodiment of the invention. From this figure the total field of view of the system is at most around 7 microns.
Fig. 6 is a graph of MTF vs Field of the telecentric lens according to the embodiment of the invention, wherein the horizontal axis represents the normalized relative image height of the optical system, the vertical axis represents the contrast of the system, and the modulus transfer function represents the value from 0 to 1, and the higher the value represents the higher the contrast, it can be seen that the total Field of view reaches substantially 0.35 or more at 80 lp/mm.
Parameters of the coaxial telecentric lens system: OO' ═ 357.5; EFL 32.2-34.5; h-30; WF/# ═ 12, PMAG (magnification) ═ 1.5X, see fig. 7 for details.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art will understand that various changes, modifications and substitutions can be made without departing from the spirit and scope of the invention as defined by the appended claims. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (8)
1. A coaxial telecentric lens comprising, in order from an object plane (0) to an image plane (10):
a first lens (1) with positive optical power, the object side surface of which is convex and comprises a first spherical surface (convex surface) and a second spherical surface (convex surface);
a second lens (2) with positive focal power, the object side surface of which is convex and comprises a third spherical surface (convex surface) and a fourth spherical surface (convex surface);
a third lens (3) with negative focal power, the object side surface of which is concave and comprises a fifth spherical surface (concave surface) and a sixth spherical surface (concave surface);
a fourth lens (4) with positive optical power, the object side surface of which is convex and comprises a seventh spherical surface (convex surface) and an eighth spherical surface (concave surface);
a fifth lens (5) with positive optical power, the object side surface of which is convex, comprising a ninth sphere (convex surface) and a tenth sphere (convex surface or plane);
a sixth lens (6) having a negative refractive power, the object-side surface of which is concave, and which includes an eleventh spherical surface (concave surface) and a twelfth spherical surface (concave surface);
a seventh lens (7) with positive optical power, the object side surface of which is convex, comprising a thirteenth spherical surface (convex surface) and a fourteenth spherical surface (convex surface);
the fourth spherical surface of the second lens (2) is cemented with the fifth spherical surface of the third lens (3), the sixth spherical surface of the third lens (3) is cemented with the seventh spherical surface of the fourth lens (4), namely the second lens (2), the third lens (3) and the fourth lens (4) form a triple cemented lens;
the tenth spherical surface of the fifth lens (5) and the eleventh spherical surface of the sixth lens (6) are cemented, namely the fifth lens (5) and the sixth lens (6) form a double-cemented lens.
2. A coaxial telecentric lens according to claim 1 wherein a beam splitter prism (8) is disposed within the coaxial telecentric lens, the beam splitter prism being positioned close to the stop (9) and on the object side.
3. A coaxial telecentric lens according to claim 1, wherein at least one of the first lens (1) and the second lens (2) satisfies 1.45< n <1.6, 62< λ <95, where n is the refractive index of the lens glass and λ is the abbe number of the lens glass.
4. A coaxial telecentric lens according to claim 1, wherein the positive lens closest to the image side of the stop (9) in the coaxial telecentric lens satisfies 1.45< n <1.6, 62< λ <95, where n is the refractive index of glass and λ is the abbe number of glass.
5. A coaxial telecentric lens according to claim 1, wherein the coaxial telecentric lens close to the positive focal lens on the object side of the diaphragm (9) satisfies: 1.75< n <1.95, 15< λ <35, where n is the refractive index of the glass and λ is the abbe number of the glass.
6. A coaxial telecentric lens according to claim 1, wherein the coaxial telecentric lens is a conjugate imaging system and satisfies 0.8< L2/L1<2, where L1 is the distance from the object plane to the system stop (9) and L2 is the distance from the stop (9) to the image plane.
7. A coaxial telecentric lens according to claim 1, wherein the coaxial telecentric lens meets 1.7< f1/H <2.8, where f1 is the focal distance of the first lens and H is the size of the image plane (10).
8. A coaxial telecentric lens according to claim 1, wherein the coaxial telecentric lens meets 0.5< f1/f0<1, where f1 is the focal distance of the first lens and f0 is the combined focal length of all the lenses in front of the front group, i.e. the stop (9).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010742390.5A CN111736325A (en) | 2020-07-29 | 2020-07-29 | Coaxial telecentric lens |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010742390.5A CN111736325A (en) | 2020-07-29 | 2020-07-29 | Coaxial telecentric lens |
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| CN111736325A true CN111736325A (en) | 2020-10-02 |
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| CN202010742390.5A Pending CN111736325A (en) | 2020-07-29 | 2020-07-29 | Coaxial telecentric lens |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113253435A (en) * | 2021-07-08 | 2021-08-13 | 深圳市海创光学有限公司 | Coaxial telecentric lens system |
| CN114326063A (en) * | 2022-01-14 | 2022-04-12 | 广东奥普特科技股份有限公司 | High-magnification telecentric lens |
-
2020
- 2020-07-29 CN CN202010742390.5A patent/CN111736325A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113253435A (en) * | 2021-07-08 | 2021-08-13 | 深圳市海创光学有限公司 | Coaxial telecentric lens system |
| CN113253435B (en) * | 2021-07-08 | 2021-09-21 | 深圳市海创光学有限公司 | Coaxial telecentric lens system |
| CN114326063A (en) * | 2022-01-14 | 2022-04-12 | 广东奥普特科技股份有限公司 | High-magnification telecentric lens |
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Address after: 518000 6th floor, building 1, xinwujing Industrial Park, 32 cuibao Road, Baolong street, Longgang District, Shenzhen City, Guangdong Province Applicant after: Shenzhen Dongzheng Optical Technology Co.,Ltd. Address before: 518000 6th floor, building 1, xinwujing Industrial Park, 32 cuibao Road, Baolong street, Longgang District, Shenzhen City, Guangdong Province Applicant before: SHENZHEN DZO OPTICS TECHNOLOGY Co.,Ltd. |