CN110989137B

CN110989137B - Double-telecentric lens

Info

Publication number: CN110989137B
Application number: CN201911328898.4A
Authority: CN
Inventors: 杜勇刚; 谭晓军; 周峰
Original assignee: Dongguan Pomeas Precision Instrument Co ltd
Current assignee: Dongguan Pomeas Precision Instrument Co ltd
Priority date: 2019-12-20
Filing date: 2019-12-20
Publication date: 2022-03-11
Anticipated expiration: 2039-12-20
Also published as: CN110989137A

Abstract

The invention discloses a double telecentric lens, which comprises the following components in sequence from an object side to an image side: the FNo lens system comprises a first lens group G1 with positive refractive power, a diaphragm and a second lens group G2 with positive refractive power, wherein the first lens group G1 comprises a first lens G11 and a second lens G12, the second lens group G2 comprises a third lens G21, a fourth lens G22, a fifth lens G23, a sixth lens G24, a seventh lens G25 and an eighth lens G26, the third lens G21 and the fourth lens G22 are glued together to form a cemented lens, and the fifth lens G23 and the sixth lens G24 are glued together to form the cemented lens; the lens has higher resolution; in addition, a telecentric light path design is adopted, the optical distortion is less than 0.05%, and the detection precision of the lens can be effectively improved.

Description

Double-telecentric lens

Technical Field

The invention relates to the technical field of telecentric lenses, in particular to a double telecentric lens.

Background

The telecentric lens is mainly applied to precision measurement. In a precision optical measurement system, because a common optical lens has certain restriction factors, the change of the working distance can cause the change of the magnification, thereby influencing the measurement precision. The telecentric lens is mainly designed for correcting the parallax of the traditional industrial lens, and can ensure that the magnification of the obtained image is not changed within a certain object distance range, which is very important to the condition that the measured object is not on the same object plane. The telecentric lens has the characteristic light path design that the chief rays of each field of view are parallel to the optical axis, so that the measurement precision is not influenced by the change of the position height when a measured object moves in the field depth range, and the telecentric lens is widely applied to the field of related machine vision measurement.

The telecentric lens has unique optical characteristics such as high resolution, high depth of field, ultra-low distortion and unique parallel light design, along with the development of the society, the requirement on the application of the telecentric lens is higher and higher, and the optical characteristics such as the resolution, the low distortion and the like of the telecentric lens are necessary to be further improved; the relative aperture (FNo) of a general double telecentric lens only reaches F8, and if the required F number is smaller, the structure of the lens needs to be more complex and the design difficulty is larger, so that the corresponding cost is greatly increased.

Therefore, the inventors have endeavored to design a double telecentric lens to solve the above problems.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide the double-telecentric lens which meets the requirement of precision detection, has low deformation, high precision and high resolution and is simple in structure.

The invention is realized by the following modes: a double telecentric lens includes, in order from an object side to an image side: a first lens group G1 having positive refractive power, a diaphragm, and a second lens group G2 having positive refractive power, the first lens group G1 including a first lens G11 and a second lens G12, the second lens group G2 including a third lens G21, a fourth lens G22, a fifth lens G23, a sixth lens G24, a seventh lens G25, and an eighth lens G26, the third lens G21 and the fourth lens G22 being cemented together to constitute a cemented lens, the fifth lens G23 and the sixth lens G24 being cemented together to constitute a cemented lens; the first lens is a plano-convex lens or a biconvex lens with a convex surface facing the image side, the second lens is a convex-concave lens with a convex surface facing the object side, the third lens is a biconvex lens, the fourth lens is a biconcave lens, the fifth lens is a biconcave lens, the sixth lens is a biconvex lens, the seventh lens is a biconvex lens, and the eighth lens is a biconvex lens.

The following conditional expressions are also satisfied: 0.112< F1/F2<0.208,

wherein F1 is the focal length of the first lens group G1, and F2 is the focal length of the second lens group G2.

Preferably, the following conditional formula is also satisfied: 5< F212/F2<9.3,

f212 is the combined focal length of the third lens G21 and the fourth lens G22.

Preferably, the following conditional formula is also satisfied: -2.15< F234/F2< -1.15,

where F234 is the combined focal length of the fifth lens G23 and the sixth lens G24.

Preferably, the following conditional formula is also satisfied: 0.55< F256/F2<1.03,

where F256 is the combined focal length of the seventh lens G25 and the eighth lens G26.

Preferably, the first lens G11 includes a first face and a second face, the second lens G12 includes a third face and a fourth face, the cemented lens of the third lens G21 and the fourth lens G22 includes a fifth face, a sixth face and a seventh face, the cemented lens of the fifth lens G23 and the sixth lens G24 includes an eighth face, a ninth face and a tenth face, the seventh lens G25 includes a tenth face and a tenth face, the eighth lens G26 includes a tenth face and a fourteenth face, the first face, the third face, the fifth face, the tenth face and the thirteenth face are convex faces, the fourth face, the seventh face and the eighth face are concave faces, the second face is a flat face or a convex face, the tenth face is a convex face, the sixth face and the ninth face are cemented faces.

Preferably, the radii of curvature of the first face to the fourteenth face are 263.6 ± 5%, infinity, 173.5056 ± 5%, 436 ± 5%, 11.43608 ± 5%, 192.74 ± 5%, 9.132385 ± 5%, 8.68424 ± 5%, 59.2455 ± 5%, 12.307 ± 5%, 99.24651 ± 5%, 49.4124 ± 5%, 186.7967 ± 5%, and-43.1774 ± 5% in sequence, and the units are all millimeters.

Preferably, the central thickness of the first surface to the fourteenth surface is 10 ± 10%, 2 ± 10%, 10 ± 10%, 203.92 ± 10%, 2.5 ± 10%, 2 ± 10%, 7.67 ± 10%, 1 ± 10%, 4.63 ± 10%, 3.16 ± 10%, 3.86 ± 10%, 1.94 ± 10%, 4.36 ± 10%, 5 ± 10% in sequence from the air space, and the units are all millimeters.

Preferably, the refractive index and the abbe number of each lens material are, in order from the first lens G11 to the eighth lens G26: (1.603109/60.59895) ± 5%, (1.603109/60.59895) ± 5%, (1.804/46.57591) ± 5%, (1.740005/28.29941) ± 5%, (1.696796/55.52804) ± 5%, (1.622802/56.95189) ± 5%, (1.651132/55.9137) ± 5%, (1.612718/58.57816) ± 5%.

Compared with the prior art, the invention has the beneficial effects that:

1. the relative aperture (FNo) of the similar lens in the prior art only reaches F8, and the double telecentric lens can reach F6, so that the lens has higher resolution, simple structure and saved design and manufacturing cost;

2. the method can support a larger measurement range under the same multiplying power of a 1-inch target surface;

3. in addition, the object side and image side double-side telecentric optical path design is adopted, the optical distortion is less than 0.05 percent, the shape of the measured object is really restored, the detection precision of the lens can be effectively improved, and the accuracy of the measured data and the repeatability of the measured data at different depth of field positions are ensured.

Drawings

FIG. 1 is a schematic cross-sectional view of a lens assembly according to the present embodiment;

FIG. 2 is a light path diagram of the present embodiment;

FIG. 3 is a graph of imaging optical simulated spherical aberration data for the present embodiment;

FIG. 4 is a graph of data of the imaging optical simulation field curvature of the present embodiment;

fig. 5 is a graph of the imaging optical simulation distortion data of the present embodiment.

In the figure: a first lens group G1; a first lens G11; a second lens G12; a second lens group G2; a third lens G21; a fourth lens G22; a fifth lens G23; a sixth lens G24; a seventh lens G25; an eighth lens G26; an object side OP; a diaphragm S; an image plane IP; and a plane glass P.

Detailed Description

The following description of the embodiments of the present invention refers to the accompanying drawings.

As shown in fig. 1 and fig. 2, a double telecentric lens includes, in order from an object side to an image side: a first lens group G1 having positive refractive power, a diaphragm, and a second lens group G2 having positive refractive power, the first lens group G1 including a first lens G11 and a second lens G12, the second lens group G2 including a third lens G21, a fourth lens G22, a fifth lens G23, a sixth lens G24, a seventh lens G25, and an eighth lens G26, the third lens G21 and the fourth lens G22 being cemented together to constitute a cemented lens, the fifth lens G23 and the sixth lens G24 being cemented together to constitute a cemented lens;

the following conditional expressions are also satisfied:

0.112<F1/F2<0.208；

0.55<F256/F2<1.03；

-2.15<F234/F2<-1.15；

5<F212/F2<9.3；

where F1 is the focal length of the first lens group G1, F2 is the focal length of the second lens group G2, F212 is the combined focal length of the third lens G21 and the fourth lens G22, F234 is the combined focal length of the fifth lens G23 and the sixth lens G24, and F256 is the combined focal length of the seventh lens G25 and the eighth lens G26.

In the present embodiment, F1/F2 has a value of 0.16, F212/F2 has a value of 7.149, F234/F2 has a value of-1.653, and F256/F2 has a value of 0.787; the first lens element may be a biconvex lens element or a plano-convex lens element with a planar second surface, in this embodiment, the first lens element is a plano-convex lens element, the second lens element is a convex-concave lens element with a convex surface facing the object side, the third lens element is a biconvex lens element, the fourth lens element is a biconcave lens element, the fifth lens element is a biconcave lens element, the sixth lens element is a biconvex lens element, the seventh lens element is a biconvex lens element, and the eighth lens element is a biconvex lens element.

In this embodiment, the first lens G11 includes a first surface and a second surface, the second lens G12 includes a third surface and a fourth surface, the aperture of the diaphragm is a circular hole, the cemented lens of the third lens G21 and the fourth lens G22 includes a fifth surface, a sixth surface and a seventh surface, the cemented lens of the fifth lens G23 and the sixth lens G24 includes an eighth surface, a ninth surface and a tenth surface, the seventh lens G25 includes a tenth surface and a tenth surface, the eighth lens G26 includes a tenth surface and a tenth surface, the first surface, the third surface, the fifth surface, the tenth surface and the fourteenth surface are convex surfaces, the fourth surface, the seventh surface and the eighth surface are concave surfaces, the second surface is a plane, and the sixth surface and the ninth surface are cemented surfaces.

In this embodiment, the radii of curvature of the first face to the fourteenth face are, in order, 263.6 ± 5%, infinity, 173.5056 ± 5%, 436 ± 5%, 11.43608 ± 5%, 192.74 ± 5%, 9.132385 ± 5%, 8.68424 ± 5%, 59.2455 ± 5%, 12.307 ± 5%, 99.24651 ± 5%, 49.4124 ± 5%, 186.7967 ± 5%, and-43.1774 ± 5%, all of which have units of millimeters, wherein the first face radius of curvature of 263.6 ± 5% means that the first face radius of curvature is in a range from 263.6% to 263.6 × 5% to 263.6+263.6 × 5%, that is, the first face radius of curvature is 250.42 mm to 276.78 mm. Other radius of curvature algorithms are consistent with the first face radius of curvature algorithm described above.

The central thickness from the first surface to the fourteenth surface and the air interval are 10 +/-10%, 2 +/-10%, 10 +/-10%, 203.92 +/-10%, 2.5 +/-10%, 2 +/-10%, 7.67 +/-10%, 1 +/-10%, 4.63 +/-10%, 3.16 +/-10%, 3.86 +/-10%, 1.94 +/-10%, 4.36 +/-10% and 5 +/-10% in sequence, and the unit is millimeter.

The refractive index and the Abbe number of each lens material are, in order from the first lens G11 to the eighth lens G26: (1.603109/60.59895) ± 5%, (1.603109/60.59895) ± 5%, (1.804/46.57591) ± 5%, (1.740005/28.29941) ± 5%, (1.696796/55.52804) ± 5%, (1.622802/56.95189) ± 5%, (1.651132/55.9137) ± 5%, (1.612718/58.57816) ± 5%.

In the present embodiment, the radius of curvature R, the center thickness/air interval D, the refractive index Nd of the mirror, and the dispersion coefficient Vd of fourteen surfaces in total of the diaphragm and the eight lenses respectively satisfy the following conditions, as shown in table 1, where the fifteenth surface and the sixteenth surface are two surfaces of the plane glass P.

Table 1: system parameters of telecentric lens of the embodiment

In which, fig. 3, 4 and 5 are simulation data of spherical aberration, curvature of field and distortion according to the embodiment of the present invention. It is clear from this that the present invention is excellent in quality, particularly, the distortion is less than 0.05%.

The above description is only a preferred embodiment of the present invention, and for those skilled in the art, the present invention should not be limited by the description of the present invention, which should be interpreted as a limitation.

Claims

1. A double telecentric lens system, comprising, in order from an object side to an image side: a first lens group G1 having positive refractive power, a diaphragm, and a second lens group G2 having positive refractive power, the first lens group G1 including a first lens G11 and a second lens G12, the second lens group G2 including a third lens G21, a fourth lens G22, a fifth lens G23, a sixth lens G24, a seventh lens G25, and an eighth lens G26, the third lens G21 and the fourth lens G22 being cemented together to constitute a cemented lens, the fifth lens G23 and the sixth lens G24 being cemented together to constitute a cemented lens; the first lens is a plano-convex lens or a biconvex lens with a convex surface facing the object side, the second lens is a convex-concave lens with a convex surface facing the object side, the third lens is a biconvex lens, the fourth lens is a biconcave lens, the fifth lens is a biconcave lens, the sixth lens is a biconvex lens, the seventh lens is a biconvex lens, and the eighth lens is a biconvex lens,

the following conditional expressions are also satisfied:

0.112< F1/F2<0.208, wherein F1 is the focal length of the first lens group G1, and F2 is the focal length of the second lens group G2.

2. A double telecentric lens according to claim 1, wherein the following conditional expression is also satisfied:

5< F212/F2<9.3, where F212 is the combined focal length of the third lens G21 and the fourth lens G22.

3. A double telecentric lens according to claim 1, wherein the following conditional expression is also satisfied:

-2.15< F234/F2< -1.15, wherein F234 is the combined focal length of the fifth lens G23 and the sixth lens G24.

4. A double telecentric lens according to claim 1, wherein the following conditional expression is also satisfied:

0.55< F256/F2<1.03, wherein F256 is the combined focal length of the seventh lens G25 and the eighth lens G26.

5. A double telecentric lens system according to claim 1, wherein the first lens G11 comprises a first surface and a second surface, the second lens G12 includes a third surface and a fourth surface, the cemented lens of the third lens G21 and the fourth lens G22 includes a fifth surface, a sixth surface and a seventh surface, the cemented lens of the fifth lens G23 and the sixth lens G24 includes an eighth face, a ninth face and a tenth face, the seventh lens G25 includes tenth and tenth faces, the eighth lens G26 includes twelfth and fourteenth faces, the first face, the third face, the fifth face, the tenth face, the thirteenth face and the thirteenth face are convex faces, the fourth surface, the seventh surface and the eighth surface are concave surfaces, the second surface is a plane or a convex surface, the tenth surface is a convex surface, and the sixth surface and the ninth surface are gluing surfaces.

6. A double telecentric lens according to claim 5, wherein the radii of curvature of the first face to the tenth face are 263.6 ± 5%, infinity, 173.5056 ± 5%, 436 ± 5%, 11.43608 ± 5%, 192.74 ± 5%, 9.132385 ± 5%, 8.68424 ± 5%, 59.2455 ± 5%, 12.307 ± 5%, 99.24651 ± 5%, 49.4124 ± 5%, 186.7967 ± 5%, 43.1774 ± 5% in the order named 263.6 ± 5%, infinity, 173.5056 ± 5%, 436 ± 5%, 99.24651 ± 5%, 49.4124 ± 5%, 186.7967 ± 5%, and 43.1774 ± 5%, all in millimeters.

7. A double telecentric lens according to claim 5, wherein the central thickness from the first surface to the fourteenth surface is 10 ± 10%, 2 ± 10%, 10 ± 10%, 203.92 ± 10%, 2.5 ± 10%, 2 ± 10%, 7.67 ± 10%, 1 ± 10%, 4.63 ± 10%, 3.16 ± 10%, 3.86 ± 10%, 1.94 ± 10%, 4.36 ± 10%, 5 ± 10% in the order of air space, and the units are millimeters.

8. A double telecentric lens system according to claim 1, wherein the refractive index and the abbe number of each lens material are, in order from the first lens G11 to the eighth lens G26: (1.603109/60.59895) ± 5%, (1.603109/60.59895) ± 5%, (1.804/46.57591) ± 5%, (1.740005/28.29941) ± 5%, (1.696796/55.52804) ± 5%, (1.622802/56.95189) ± 5%, (1.651132/55.9137) ± 5%, (1.612718/58.57816) ± 5%.