CN113589477B

CN113589477B - Near-infrared band and visible light confocal lens and magnifying lens group

Info

Publication number: CN113589477B
Application number: CN202110783981.1A
Authority: CN
Inventors: 吴帅; 陈洪平; 吴沛林
Original assignee: Guangzhou Changbudao Optical Technology Co ltd
Current assignee: Guangzhou Changbudao Optical Technology Co ltd
Priority date: 2021-07-12
Filing date: 2021-07-12
Publication date: 2023-01-06
Anticipated expiration: 2041-07-12
Also published as: CN113589477A

Abstract

The invention discloses a near-infrared band and visible light confocal lens and a magnifying lens group, wherein the lens is a main lens M _ L, the working band of the main lens M _ L (the focal length =16 mm) can be expanded from visible light to near infrared (lambda is less than or equal to 1450 nm), and when the object distance is determined to work, the working wavelength is switched without refocusing; the magnifying lens group comprises a main lens M _ L and a rear magnifying lens group R _ EXT, the rear magnifying lens group R _ EXT is installed on the image side of the main lens M _ L so as to magnify the focal length of the main lens, and the focal length before and after installation is changed from 16mm to 24mm. The magnifying lens group still keeps visible light and near infrared to have NIR confocal characteristics, and meanwhile, the clear aperture can be flexibly adjusted.

Description

Near-infrared band and visible light confocal lens and magnifying lens group

Technical Field

The invention relates to the technical field of optical devices, in particular to a fixed focus machine vision lens and a magnifying lens group thereof, which are applied to the field of industrial detection.

Background

Machine vision is to use a machine to replace human eyes for measurement and judgment. The system captures images through a lens to a CCD or COMS device, extracts the characteristics of a captured object through a special image processing system, and controls the action of field equipment according to a judgment result.

In recent years, with the rapid development of the field of machine vision, various machine vision systems are continuously developed, which puts new requirements on optical lenses matched with the machine vision systems. For the existing machine vision lens with a chip size of 2/3' and a focal length of 16mm or 25mm, the lens basically works in a visible light waveband (d, F and C light, and d light 587 nm is a dominant wavelength), in the NIR near infrared field (0.75 nm to 2.5 um), the lens needs to be designed separately to cope with the working waveband, the industrial lens of the waveband is generally applied to the food detection field, and a common industrial lens with the working waveband being visible light needs to be focused frequently when the working wavelength is switched in the wide spectral range, so that the machine vision lens has great limitation.

Therefore, there is a need for a machine vision lens that can still image clearly, i.e., without requiring refocusing, when switching from visible to near infrared operating bands.

Disclosure of Invention

Based on this, the primary objective of the present invention is to provide a near-infrared band and visible light confocal type lens and magnifier group, which provides a visible light and NIR confocal type 16mm fixed-focus machine vision lens, and after the provided special magnifier group is connected, a composite lens with a focal length of 24mm is formed, and the confocal characteristic consistent with that of the main lens is still maintained.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a near-infrared band and visible light confocal lens is a main lens M _ L, wherein the working band of the main lens M _ L (focal length =16 mm) can be expanded from visible light to near infrared (lambda is less than or equal to 1450 nm), when the object distance is determined to work, the working wavelength is switched without refocusing,

the main lens M _ L sequentially comprises a first lens group G1 and a second lens group G2 from the object side; the first lens group G1 includes, in sequence, a negative lens La, a positive lens Lb, lc and a negative lens Ld, where Lc and Ld constitute a first cemented lens group Ld1 (Lc, ld constitute +/-type); the second lens group G2 comprises a second cemented mirror LD2 (of the type minus-three cemented by Le, lf, lg), a third cemented mirror LD3 (of the type minus-minus +/-cemented by Lg, lh), a positive lens Lj, and a fourth cemented mirror (of the type minus-plus cemented by Lk, ll) in sequence; wherein the diaphragm Stop is arranged between G1 and G2 and is fixed in position relative to G1 and G2.

The lens is applied to the field of machine vision, the optical lens M _ L with the focal length of 16mm has clear imaging from the object distance of 0.3M to infinity, the working waveband can be expanded from visible light to a near infrared region (lambda is less than or equal to 1450 nm), and zero virtual focus of the working waveband is switched.

A focal length f (G1) of the first lens group G1, and a focal length f (G2) of the second lens group G2 satisfy the following conditional expression (1) and conditional expression (2):

-250<f(G1)<-200……(1)

12<f(G2)<15……(2)。

further, the focal length f (LD 1) of the double cemented lens LD1 in the first lens group G1, and the respective focal lengths f (LD 2), f (LD 3), f (LD 4) of the double cemented lenses LD2, LD3, LD4 in the second lens group satisfy the following conditional expressions (3), (4), (5), and (6):

0.13<f(LD1)/f(G1)<0.15……(3)

-19<f(LD2)/f(G2)<-17……(4)

13<f(LD3)/f(G2)<15……(5)

9<f(LD4)/f(G2)<11.5……(6)。

further, the refractive index n (Lb) and the abbe number V (Lb) of the positive lens Lb in the first lens group G1 satisfy conditional expressions (7) and (8):

1.83<n(Lb)<1.95……(7)

34<V(Lb)<43……(8)。

further, the first lens group G1 and the second lens group G2, in which the elements of the cemented lens group (including double-cemented and triple-cemented) each have an abbe number V (Lc), V (Ld) and V (Le), V (Lf), V (Lg), and V (Lh), V (Li) and V (Lk), V (Ll), satisfy the following conditional expressions (9), (10), (11) (12) and (13):

16<V(Lc)-V(Ld)<25……(9)

5<V(Lf)-V(Le)<10……(10)

5<V(Lf)-V(Lg)<10……(11)

-40<V(Lh)-V(Li)<-35……(12)

40<V(Lk)-V(Ll)<45……(13)。

a near-infrared band and visible light confocal type magnifying lens group comprises a main lens M _ L and a rear magnifying lens group R _ EXT, wherein the rear magnifying lens group R _ EXT is installed on the image side of the main lens M _ L so as to magnify the focal length of the main lens, and the focal length before and after installation is changed from 16mm to 24mm;

the rear magnifying lens group R _ EXT includes, in order from the object side, a cemented lens group RD1 (composed of Ra and Rb), a negative lens Rc, and a cemented lens group RD2 (a-plus-minus-three cemented structure composed of RD, re and Rf), where the lens group RD1 is formed by cementing a negative lens (Ra) with a concave surface facing the image side and a positive lens (Rb) with a convex surface facing the object side.

Further, the focal length f (RD 1) of the lens group RD1, the focal length f (RD 2) of the RD2, and the focal length f (R) of the rear magnifier, satisfy the following conditional expressions (14) and (15):

-0.9<f(RD1)/f(R)<-0.7……(14)

0.8<f(RD2)/f(R)<01……(15)

further, in the lens group RD1 of the rear magnifier group R _ EXT, the abbe number V (Ra) of the negative lens Ra, the abbe number V (Rb) of the positive lens Rb, the abbe number V (RD) of the negative lens RD in the lens group RD2, the abbe number V (Re) of the positive lens Re, the abbe number V (Rf) of the negative lens Rf satisfy the following conditional expressions (16), (17), (18), (19) and (20):

8<V(Ra)-V(Rb)<11……(16)

30<V(Re)-V(Rd)<40……(17)

0<V(Re)-V(Rf)<10……(18)

39<V(Ra)<44……(19)

34<V(Rd)<42……(20)

the refractive index n (Ra) of the negative lens Ra in the lens group RD1, the refractive index n (RD) of the negative lens RD in the lens group RD2, satisfy conditional expressions (21) and (22):

1.80<n(Ra)<1.85……(21)

1.83<n(Rd)<1.95……(22)

the main lens M _ L and the rear magnifying lens group R _ EXT are combined into an integral optical system, and the interval d (unit is mm) meets the following conditional expression (23):

0.9<d<1.9……(23)

furthermore, the lens surface types of the main lens M _ L and the rear magnifying lens set R _ EXT are spherical.

The main lens M _ L and the rear magnifier group R _ EXT may include optical elements other than lenses having substantially no optical power, such as an aperture stop and a filter, in addition to the components mentioned as the constituent elements. The abbe number appearing in the conditional expression is based on the d-line.

The beneficial effects of the invention are:

the invention provides a visible light and near infrared NIR confocal type 16mm fixed focus machine vision lens, and is connected with a special magnifying lens group with negative focal power, the focal length is enlarged to 24mm, the visible light and near infrared NIR confocal characteristics are still kept, and meanwhile, the clear aperture can be flexibly adjusted.

Drawings

FIG. 1 is an optical cross-sectional view of a magnifying lens set connected to a rear end of a main lens M _ L at an object distance of 2M.

FIG. 2 is a diagram of aberration diagrams of the main lens M _ L at an object distance of 2M (including FIGS. 2-1, 2-2, 2-3, and 2-4).

FIG. 3 is a diagram of aberration diagrams of the main lens M _ L followed by the magnifier at 2M object distance (including FIGS. 3-1, 3-2, 3-3, and 3-4).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.

Referring to fig. 1, a sectional view of a lens structure of a main lens combined with a rear magnifier group according to the present invention is shown. In fig. 1, the left side represents the object side, and the right side represents the image side, and the illustrated aperture stop represents a position on the optical axis z, not necessarily a size and a shape.

The rear magnifying lens group R _ EXT has negative focal power and is arranged on the image side of the main lens M _ L to magnify the focal length of the main lens.

And the entire system in which the magnifier group R _ EXT is mounted in the lens M _ L is simply referred to as a combining optical system.

The optical lens M _ L is applied to the field of machine vision, has a focal length of 16mm, can be used for clearly imaging from an object distance of 0.3M to infinity, can be used for expanding a working waveband from visible light to a near infrared region (lambda is less than or equal to 1450 nm), and can be used for switching the working waveband into zero virtual focus.

Specifically, the lens M _ L is composed of, in order from the object side, a first lens group G1 having negative power, and a second lens group G2 having positive power.

The first lens group G1 includes, in sequence, a negative lens La, a positive lens Lb, lc and a negative lens Ld, where Lc and Ld constitute a first cemented lens group Ld1 (Lc, ld constitute +/-type); the second lens group G2 sequentially includes a second cemented mirror LD2 (of the type minus-three cemented by Le, lf, lg), a third cemented mirror LD3 (of the type minus-plus cemented by Lh, li), a positive lens Lj, and a fourth cemented mirror (of the type minus-plus cemented by Lk, ll). Wherein the diaphragm Stop is disposed between G1 and G2 and is fixed in position relative to G1 and G2.

The negative power rear magnifying lens group is mounted on the image side of the main lens to magnify the focal length of the main lens, and the focal length before and after mounting is changed from 16mm to 24mm. Wherein the rear magnifying lens comprises a cemented lens group RD1 (Ra, rb), a negative lens Rc, and an adhesive lens group RD2 (of a type of bonding power minus three composed of Rd, re and Rf).

After the main lens M _ L and the rear magnifying lens set R _ EXT are combined into the integral optical system, when the interval d meets the conditional expression (23), the combined optical system can obtain the best image quality within the object distance range of more than or equal to 300 mm:

0.9<d<1.9……(23)。

first, a numerical embodiment of the main lens M _ L will be explained. Specific lens data corresponding to the M _ L single body is shown in table 1, and data relating to specifications is shown in table 2, and respective aberration diagrams of the main lens M _ L in the 2M object distance state are given in fig. 2.

Noodle numbering	Radius of the pipe	Surface interval	Refractive index	Abbe number
					1	88.5535	1.000	1.73	28.3
2	20.3995	2.515
					3	25.5075	3.074	1.91	35.3
4	-86.6817	0.120
					5	13.7935	5.055	1.46	90.3
6	-42.1821	1.000	1.52	64.2
					7	7.0557	5.187
8	Infinite number of elements	3.351
					9	-8.9972	4.238	1.52	64.2
10	-519.7059	3.925	1.57	71.3
					11	-10.4755	1.000	1.52	64.2
12	-14.8098	0.120
					13	-30.9655	1.000	1.85	32.3
14	127.7535	3.712	1.57	71.3
					15	-17.9830	0.120
16	29.3662	4.315	1.57	71.3
					17	-26.3748	0.120
18	19.4203	5.462	1.46	90.3
					19	-21.0849	1.605	1.8	46.8
20	377.0881	14.0830

TABLE 1

Focal length f	16.18
		Back coke BFL	14.0830
F value	1.5400
		Angle of view 2 omega	37.6800

TABLE 2

Next, the rear magnifier group R _ EXT in the above embodiment will be described. Fig. 1 shows a cross-sectional view showing the entire configuration in a state where the rear magnifier group R _ EXT is attached to the main lens M _ L. Table 3 shows lens data of the combining optical system in which the rear magnifier group R _ EXT is attached to the main lens M _ L, and table 4 shows data relating to specifications. Fig. 3 shows aberration diagrams of the synthesizing optical system.

Noodle number	Radius of the pipe	Surface interval	Refractive index	Abbe number
					1	88.5535	1.000	1.73	28.3
2	20.3995	2.515
					3	25.5075	3.074	1.91	35.3
4	-86.6817	0.120
					5	13.7935	5.055	1.46	90.3
6	-42.1821	1.000	1.52	64.2
					7	7.0557	5.187
8	Infinite number of elements	3.351
					9	-8.9972	4.238	1.52	64.2
10	-519.7059	3.925	1.57	71.3
					11	-10.4755	1.000	1.52	64.2
12	-14.8098	0.120
					13	-30.9655	1.000	1.85	32.3
14	127.7535	3.712	1.57	71.3
					15	-17.9830	0.120
16	29.3662	4.315	1.57	71.3
					17	-26.3748	0.120
18	19.4203	5.462	1.46	90.3
					19	-21.0849	1.605	1.8	46.8
20	377.0881	1.010
					21	34.0935	0.800	1.83	42.7
22	7.7194	3.706	1.65	33.9
					23	-26.9684	0.100
24	-264.8677	0.800	1.57	71.3
					25	28.2636	3.067
26	-11.8860	0.800	1.91	35.3
					27	32.8597	4.137	1.49	70.4
28	-6.0957	2.322	1.59	68.3
					29	-9.3359	6.000
30	Unlimited in size	0.00

TABLE 3

Focal length f	24.0500
		Back coke BFL	6.0000
F value	2.2900
		Angle of view 2 omega	25.7100

TABLE 4

Fig. 2 shows respective aberration diagrams of the main lens unit. In addition, spherical aberration, astigmatism, field curvature aberration, distortion aberration, and vertical axis aberration are shown in order from the left side of fig. 2. In each aberration diagram showing spherical aberration, astigmatism, field curvature, and distortion aberration (fig. 2-1, 2-2, 2-3, and 2-4 are aberration diagrams of spherical aberration, astigmatism, field curvature, distortion aberration, and vertical axis chromatic aberration, respectively, and also in fig. 3), the aberration with the d-line (λ =587.6 nm) as a reference wavelength is shown. In the spherical aberration diagram, aberrations with respect to a d-line (λ =587.6 nm), a C-line (λ =656.3 nm), an F-line (λ =486.1 nm), a g-line (λ =435.8 nm), an s-line (λ =852.1 nm), a YAG wavelength (λ =1060 nm), and an infrared wavelength (λ =1450 nm) are respectively indicated in the vicinities by wavelength names in conjunction with dashed lines. In the astigmatism diagrams, aberrations in the sagittal direction and the meridional direction are represented by S and T above the curves, respectively. In the vertical axis chromatic aberration diagram, aberrations about a d-line (λ =587.6 nm), a C-line (λ =656.3 nm), an F-line (λ =486.1 nm), and a g-line (λ =435.8 nm) are represented by wavelength names in the vicinity of the respective aberrations in combination with dashed lines. Since the near infrared spectrum imaging except visible light is a black and white picture, the vertical axis chromatic aberration of the near infrared spectrum is generally not discussed. In addition, f.no of the spherical aberration diagrams indicates the F value, and ω of the other aberration diagrams indicates the half angle of view. The meanings of these symbols are explained using fig. 2 as an example, but the same applies to fig. 3. The aberration diagrams shown in fig. 2 and 3 are aberration diagrams in a state where the working distance is 2 m.

In a word, the 16mm fixed-focus machine vision lens with the visible light and near infrared NIR confocal type designed by the invention can be connected with a special rear-mounted magnifying lens group with negative focal power in a rear mode, the focal length is enlarged to 24mm, the visible light and near infrared NIR confocal characteristics are still kept, and meanwhile, the clear aperture can be flexibly adjusted.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A near-infrared band and visible light confocal lens is characterized in that the lens comprises a main lens M _ L, wherein the working band of the main lens M _ L can be expanded from visible light to near infrared, and when the object distance is determined to work, the working wavelength is switched without refocusing;

the main lens M _ L consists of a first lens group G1, a diaphragm Stop and a second lens group G2 in sequence from the object side; the first lens group G1 consists of a negative lens La, a positive lens Lb, an Lc and a negative lens Ld in sequence, wherein the Lc and the Ld form a first cemented lens group LD1; the second lens group G2 consists of a meniscus negative lens Le with a convex surface facing the image side, a meniscus positive lens Lf with a convex surface facing the image side, a meniscus negative lens Lg with a convex surface facing the image side, a biconcave negative lens Lh, a biconvex positive lens Li, a biconvex positive lens Lj, a biconvex positive lens Lk and a biconcave negative lens LI in sequence, the meniscus negative lens Le, the meniscus positive lens Lf and the meniscus negative lens Lg form a second cemented lens LD2, the biconvex negative lens Lh and the biconvex positive lens Li form a third cemented lens LD3, and the biconvex positive lens Lk and the biconcave negative lens LI form a fourth cemented lens LD4; wherein the diaphragm Stop is arranged between G1 and G2 and is fixed in position relative to G1 and G2.

2. The lens of claim 1, wherein the focal length f (G1) of the first lens group G1 satisfies the following formula: 250mm < -f (G1) < -200mm, and the focal length f (G2) of the second lens group G2 satisfies the formula of 12mm < -f (G2) <15mm.

3. The lens of the near-infrared band and visible light confocal type according to claim 2, wherein the focal length f (LD 1) of first cemented lens group LD1 in first lens group G1 satisfies the formula of 0.13 stra f (LD 1)/f (G1) <0.15, the focal length f (LD 2) of second cemented lens LD2 in second lens group satisfies the formula of-19 stra f (LD 2)/f (G2) < -17, the focal length of ld3 satisfies the formula of 13 stra f (LD 3)/f (G2) <15, the focal length f (LD 4) of ld4 satisfies the formula: 9-woven fabric f (LD 4)/f (G2) <11.5; wherein f (LD 3) and f (LD 4) are the focal lengths of LD3 and LD4, respectively.

4. The lens of claim 1, wherein the refractive index n (Lb) of the positive lens Lb in the first lens group G1 satisfies the following formula: 1.83-n (Lb) <1.95, abbe number V (Lb) satisfying the formula: 34 are woven into a fabric composed of a plurality of layers of fabric composed of yarns.

5. The lens of claim 4, wherein the first lens group G1 and the second lens group G2 have Abbe numbers V (Lc), V (Ld), V (Le), V (Lf), V (Lg), V (Lh), V (Li), V (Lk), and V (Ll) of elements satisfying the following equations:

v (Lc) and V (Ld) satisfy the formulas of 16 & lt V (Lc) -V (Ld) & lt 25,

v (Lf) and V (Le) satisfy the formulas of 5 & lt V (Lf) -V (Le) & lt 10,

v (Lf), V (Lg) satisfy the formula of 5-V (Lf) -V (Lg) <10,

v (Lh), V (Li) satisfy the formula: -40-n (Lh) -V (Li) < -35,

v (Lk), V (Ll), the formula is satisfied, 40 & lt V (Lk) -V (Ll) & lt 45,

wherein V (Lc) is an abbe number of the positive lens Lc, V (Ld) is an abbe number of the negative lens Ld, V (Lf) is an abbe number of the meniscus positive lens Lf, and V (Le) is an abbe number of the meniscus negative lens Le; v (Lg) is the abbe number of the meniscus negative lens Lg, V (Lh) is the abbe number of the biconcave negative lens Lh, V (Li) is the abbe number of the biconvex positive lens Li, V (Lk) is the abbe number of the biconvex positive lens Lk, and V (Ll) is the abbe number of the biconcave negative lens Li.

6. A magnifier group of the near infrared band and visible light confocal type lens according to claim 1, the magnifier group comprises a main lens M _ L and a rear magnifier group R _ EXT, the rear magnifier group R _ EXT is installed at the image side of the main lens M _ L to magnify the focal length of the main lens, the focal length before and after installation is changed from 16mm to 24mm;

the rear magnifying lens group R _ EXT is composed of a cemented lens group RD1 with a convex surface facing the object side, a negative lens Rc and a cemented lens group RD2 in sequence from the object side, wherein the cemented lens group RD1 is composed of a meniscus negative lens Ra and a biconvex positive lens Rb, and the cemented lens group RD2 is composed of a biconcave negative lens Rd, a biconvex positive lens Re and a meniscus negative lens Rf.

7. The zoom lens group of a lens of a near infrared band and visible light confocal type according to claim 6, wherein the focal length f (RD 1) of the lens group RD1 and the focal length f (R) of the rear zoom lens satisfy the following formula: -0.9 and yarn (RD 1)/yarn (R) < -0.7, the focal length f (RD 2) of RD2 and the focal length f (R) of the rear magnifier satisfy the following formula: 0.8 are woven as f (RD 2)/f (R) <1.

8. The magnifier group of a lens assembly of a near infrared band and visible light confocal type according to claim 6, wherein in the lens group RD1 of the rear magnifier group R _ EXT, abbe number V (Ra) of the negative lens Ra and abbe number V (Rb) of the positive lens Rb satisfy the following formula: 8-Ap V (Ra) -V (Rb) <11, abbe number V (Rd) of the negative lens Rd and Abbe number V (Re) of the positive lens Re in the lens group RD2 satisfy the following formula: 30< -V (Re) -V (Rd) <40, abbe number V (Re) of the positive lens Re and Abbe number V (Rf) of the negative lens Rf satisfy the following formula: 0< -V (Re) -V (Rf) <10, wherein 39< -V (Ra) <44, 34< -V (Rd) <42.

9. The magnifier group according to claim 6, wherein the refractive index n (Ra) of the negative lens Ra in the lens group RD1 satisfies the following formula: 1.80< -n (Ra) <1.85, and the refractive index n (RD) of the negative lens RD in the lens group RD2 satisfies the formula: 1.83 sP n (Rd) <1.95.

10. The magnifier group of near infrared band and visible light confocal lens according to claim 6, wherein the distance d between the main lens M _ L and the rear magnifier group R _ EXT satisfies the following equation after they are combined into the whole optical system: the 0.9mm were constructed so as to have d-groups of 1.9mm.