CN116088147A

CN116088147A - Collimation lens

Info

Publication number: CN116088147A
Application number: CN202310062097.8A
Authority: CN
Inventors: 章彬炜; 桂嘉乐; 曾昊杰
Original assignee: Jiangxi Lianyi Optics Co Ltd
Current assignee: Jiangxi Lianyi Optics Co Ltd
Priority date: 2023-01-16
Filing date: 2023-01-16
Publication date: 2023-05-09

Abstract

The invention discloses a collimating lens, which sequentially comprises the following components from a laser emitter end to a measured object end: the first lens with positive focal power has a convex object side surface and a concave image side surface; the second lens with negative focal power has a concave object side surface and a convex image side surface; a third lens having positive optical power, the image side surface of which is convex; a diaphragm; wherein, the diaphragm is positioned between the third lens and the measured object; the first lens and the second lens are made of plastic materials, and the third lens is made of molded glass materials. According to the collimating lens provided by the invention, three lenses are adopted, and the specific surface shape and focal power are set for each lens, so that not only can clear imaging be realized by effectively utilizing lenses with different refractive indexes and focal distances, but also the collimating lens can be subjected to collimating projection through each lens, so that the collimating lens is ensured to have smaller distortion, and meanwhile, the change of the overall performance of the collimating lens at different temperatures is ensured to be smaller, thereby realizing the purpose of enhancing the focal distance stability of the collimating lens.

Description

Collimation lens

Technical Field

The invention relates to the technical field of imaging lenses, in particular to a collimating lens.

Background

In recent years, 3D photographic technology has been developed rapidly, and the optical sensing technology based on 3D structured light can be used for face recognition, gesture recognition, photographic function enhancement and new application of AR, and can convert an optical image from a past two-dimensional space into a three-dimensional space, so that user experience is more real and clear.

The 3D structured light refers to projecting specific laser information on the surface of an object, collecting by a camera, and then calculating the position and depth of the object through the change of the optical information caused by the object, thereby restoring the whole three-dimensional space. Specific laser information is a very important index in 3D structured light technology, so the requirement for projecting laser information onto the surface of the object to be measured is high. Such a collimator lens, which projects an array of point light sources emitted at a specific solid angle on the laser surface of a VCSEL (vertical cavity surface emitting laser) onto the surface of a measured object, is a key part of the 3D imaging quality.

In the existing products, the focal length f of the lens is greatly changed along with the change of the ambient temperature, so that the angle of the light projected by the lens is obviously changed, the original light information is changed, the calculation of the whole system is error, and the contour recovery precision of the three-dimensional object is affected; also, the degree of collimation decreases with temperature changes, which also results in a decrease in the sharpness of the system in recovering a three-dimensional object. Therefore, it is important to keep the focal length of the lens stable so that the angle of view and the degree of collimation of the light information projected onto the object to be measured do not change greatly when the ambient temperature is changed.

Disclosure of Invention

Therefore, the invention aims to provide a collimating lens, so that the angle of view and the degree of collimation of light information projected to an object to be measured do not change greatly under different temperature occasions.

The embodiment of the invention realizes the aim through the following technical scheme.

The invention provides a collimating lens, which comprises three lenses in sequence from a laser emitter end to a measured object end, wherein the three lenses comprise: the first lens with positive focal power has a convex object side surface and a concave image side surface; the second lens with negative focal power has a concave object side surface and a convex image side surface; a third lens having positive optical power, the image side surface of which is convex; a diaphragm; the laser emitter end is an object side, the object end to be measured is an image side, the first lens and the second lens are made of plastic materials, and the third lens is made of glass materials.

Compared with the prior art, the collimating lens provided by the invention has the advantages that the first lens, the second lens and the third lens are arranged, and the specific surface shape and the specific focal power are arranged for each lens, so that clear imaging can be realized by effectively utilizing lenses with different refractive indexes and focal distances, and the collimating lens can be used for collimating projection, so that the collimating lens is ensured to have smaller distortion, meanwhile, the integral performance of the collimating lens is ensured to have smaller change at different temperatures, the focal length stability of the collimating lens is enhanced, and the aim that the angle of view and the collimation degree of optical information projected to an object to be measured do not change greatly under different temperature occasions is fulfilled.

Drawings

The foregoing and/or additional aspects and advantages of the present invention will be apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural diagram of a collimator lens according to a first embodiment of the present invention.

Fig. 2 is a graph showing a field curvature of a collimator lens according to a first embodiment of the present invention.

Fig. 3 is a distortion chart of a collimator lens according to a first embodiment of the present invention.

Fig. 4 is a schematic view of an imaging collimation degree of a collimating lens according to a first embodiment of the present invention.

Fig. 5 is a schematic structural diagram of a collimating lens according to a second embodiment of the present invention.

Fig. 6 is a graph showing a field curvature of a collimator lens according to a second embodiment of the present invention.

Fig. 7 is a distortion chart of a collimating lens according to a second embodiment of the present invention.

Fig. 8 is a schematic diagram of an imaging collimation degree of a collimating lens according to a second embodiment of the present invention.

Fig. 9 is a schematic structural diagram of a collimating lens according to a third embodiment of the present invention.

Fig. 10 is a field curve diagram of a collimator lens according to a third embodiment of the present invention.

Fig. 11 is a distortion graph of a collimator lens according to a third embodiment of the present invention.

Fig. 12 is a schematic view of an imaging collimation degree of a collimating lens according to a third embodiment of the present invention.

Detailed Description

In order that the objects, features and advantages of the invention will be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Several embodiments of the invention are presented in the figures. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The embodiment of the invention provides a collimating lens, which sequentially comprises the following components from a laser emitter end to a measured object end: the optical centers of the first lens, the second lens, the third lens and the diaphragm are positioned on the same straight line; the laser emitter end is an object side, the object end to be measured is an image side, the first lens and the second lens are made of plastic materials, and the third lens is made of glass materials.

Specifically, the first lens has positive focal power, and the object side surface of the first lens is a convex surface and the image side surface of the first lens is a concave surface; the second lens has negative focal power, and the object side surface of the second lens is concave and the image side surface of the second lens is convex; the third lens has positive focal power, and the image side surface of the third lens is a convex surface; the first lens, the second lens and the third lens are all aspheric lenses; the diaphragm is close to the end of the measured object.

According to the invention, through arranging the first lens, the second lens and the third lens and arranging the specific surface shape and the specific focal power for each lens, not only can clear imaging be realized by effectively utilizing lenses with different refractive indexes and focal lengths, but also the collimating projection can be carried out through each lens, so that the collimating lens is ensured to have smaller distortion, meanwhile, the change of the overall performance of the collimating lens at different temperatures is ensured to be smaller, the focal length stability of the collimating lens is enhanced, and the aim that the angle of view and the collimation degree of optical information projected to an object to be measured are not changed greatly under different temperature occasions is fulfilled.

In some embodiments, the collimating lens satisfies the following conditional expression:

1.5＜Nd1＜1.6；(1)

1.5＜Nd2＜1.6；(2)

1.6＜Nd3＜1.7；(3)

wherein Nd1 represents a material refractive index of the first lens, nd2 represents a material refractive index of the second lens, and Nd3 represents a material refractive index of the third lens. The refractive indexes of the lens materials are reasonably matched to meet the conditional expressions (1), (2) and (3), so that the aberration of the collimating lens is corrected, and the imaging quality of the collimating lens is improved.

(dn/dt) ₁ ×TCE ₁ ×f ₁ ＞-40×10 ^-3 mm/℃ ² ；(4)

(dn/dt) ₂ ×TCE ₂ ×f ₂ ＜40×10 ^-3 mm/℃ ² ； (5)

(dn/dt) ₃ ×TCE ₃ ×f ₃ ＞-1×10 ^-3 mm/℃ ² ； (6)

wherein, (dn/dt) ₁ Indicating the temperature coefficient of refractive index, TCE, of the first lens in the range of 0-60 DEG C ₁ Representing the coefficient of thermal expansion, f, of the first lens ₁ Representing the focal length of the first lens at normal temperature (20 ℃); (dn/dt) ₂ Indicating the temperature coefficient of refractive index, TCE, of the second lens in the range of 0-60 DEG C ₂ Representing the coefficient of thermal expansion, f, of the second lens ₂ Represents the focal length of the second lens at normal temperature (20 ℃); (dn/dt) ₃ Indicating the temperature coefficient of refractive index, TCE, of the third lens in the range of 0-60 DEG C ₃ Representation ofThe thermal expansion coefficient f of the third lens ₃ The focal length of the third lens at normal temperature (20 ℃ C.) is shown. The above conditional expressions (4), (5) and (6) are satisfied, the rate of change of the refractive index of each lens along with the temperature is definitely limited, and the refractive index is reasonably matched according to different thermal expansion characteristics of lens materials, so that the stability of the focal length of the whole system is realized, the collimation effect of the lens is ensured, and the whole three-dimensional space is restored under the condition of different temperatures without changing the original light information.

3.5＜f1/r1＜4.5；(7)

wherein f1 represents a focal length of the first lens, and r1 represents a radius of curvature of the object side surface of the first lens. The above conditional expression (7) is satisfied, the shape of the object side surface of the first lens of the collimating lens can be limited, which is beneficial to the processing and manufacturing of the lens, and the tolerance sensitivity can be reduced.

-0.5＜r1/r6＜-0.3；(8)

where r1 represents a radius of curvature of the first lens object-side surface, and r6 represents a radius of curvature of the third lens image-side surface. The condition (8) is satisfied, the object side surface of the first lens element and the image side surface of the third lens element of the collimating lens can be restricted from being opposite in direction, the light passing through the third lens element can be converged on the imaging surface, and meanwhile, the collimating effect of the lens element can be improved.

-3＜f/r6＜-2；(9)

where f represents a system focal length of the collimating lens, and r6 represents a radius of curvature of the image side surface of the third lens. Satisfying the above conditional expression (9) can limit the shape of the image side surface of the third lens, facilitate lens processing, and reduce tolerance sensitivity.

-2.0<r2/r4<-0.3；(10)

-0.2<r3/r5<0.02；(11)

wherein r2 represents a radius of curvature of the image side surface of the first lens, r3 represents a radius of curvature of the object side surface of the second lens, r4 represents a radius of curvature of the image side surface of the second lens, and r5 represents a radius of curvature of the object side surface of the third lens. The conditional expressions (10) and (11) are satisfied, and the image side shapes of the first lens and the second lens and the object side shapes of the second lens and the third lens can be effectively controlled, so that the aberration of the collimating lens can be reduced, the curvature of field can be balanced, and the imaging quality of the collimating lens can be improved.

-2<f3/f2<0； (12)

wherein f2 represents the focal length of the second lens, and f3 represents the focal length of the third lens. The focal power ratio of the second lens and the third lens can be effectively limited by meeting the conditional expression (12), the aberration of the collimating lens is reduced, and the imaging quality is improved.

TTL/f＜0.85； (13)

wherein TTL represents the total optical length of the collimating lens, and f represents the system focal length of the collimating lens. The proportional relation between the total length of the system and the focal length of the system can be limited by meeting the conditional expression (13), and the equalization of the long focal length and the miniaturization of the system can be realized. Specifically, the total optical length TTL of the collimating lens is smaller than 6.2mm, the system focal length f of the collimating lens is larger than 6.5mm, and the method is favorable for guaranteeing better optical characteristics and is also suitable for realizing the algorithm of 3D structured light.

0.4＜CT1/CT2＜1.1； (14)

wherein CT1 represents the center thickness of the first lens and CT2 represents the center thickness of the second lens. The above conditional expression (14) is satisfied, the ratio of the center thickness of the second lens to the center thickness of the first lens of the collimating lens is limited, and the center thickness of the lens is properly configured, so that the processing, the manufacturing and the assembly of the optical lens group are facilitated.

0＜(CT1+CT3)/CT2＜2；(15)

wherein CT1 represents the center thickness of the first lens, CT2 represents the center thickness of the second lens, and CT3 represents the center thickness of the third lens. Satisfying the above conditional expression (15), the beam width is widened, the homogenization of the infrared beam emitted by the laser emitter is ensured, and the collimation effect of the lens is improved.

The invention is further illustrated in the following examples. In each embodiment, the thickness and curvature radius of each lens in the collimating lens are different, and the specific difference can be seen from the parameter table of each embodiment. The following examples are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following examples, and any other changes, substitutions, combinations or simplifications that do not depart from the gist of the present invention are intended to be equivalent substitutes within the scope of the present invention.

In various embodiments of the present invention, the aspherical profile of each lens satisfies the following equation:

where z is the distance sagittal height from the aspherical surface vertex when the aspherical surface is at a position of height h in the optical axis direction, c is the paraxial curvature of the surface, k is the quadric coefficient, A _2i The aspherical surface profile coefficient of the 2 i-th order.

First embodiment

Referring to fig. 1, a schematic structural diagram of a collimator lens 100 according to a first embodiment of the present invention is shown, where the collimator lens 100 includes, in order from an object side to an imaging surface S7 along a paraxial direction: a first lens L1, a second lens L2, a third lens L3, and a stop ST. Specifically, the first lens element L1 has positive refractive power, wherein an object-side surface S1 thereof is convex, and an image-side surface S2 thereof is concave; the second lens element L2 has negative refractive power, wherein an object-side surface S3 thereof is concave and an image-side surface S4 thereof is convex; the third lens element L3 has positive refractive power, and an object-side surface S5 thereof is convex at a paraxial region and an image-side surface S6 thereof is convex. The first lens L1 and the second lens L2 are plastic aspherical lenses, and the third lens L3 is a molded glass aspherical lens.

The relevant parameters of each lens in the collimating lens 100 provided in this embodiment are shown in table 1.

TABLE 1

The surface profile coefficients of the aspherical surfaces of the collimator lens 100 in this embodiment are shown in table 2.

TABLE 2

In this embodiment, schematic diagrams of curvature of field, distortion and imaging collimation of the collimator lens 100 are shown in fig. 2, 3 and 4, respectively.

Second embodiment

Referring to fig. 5 for a schematic structural diagram of a collimator lens 200 provided in the present embodiment, the collimator lens 200 in the present embodiment has substantially the same structure as the collimator lens 100 in the first embodiment, except that an object side surface of a third lens element of the collimator lens 200 is a concave surface.

The relevant parameters of each lens in the collimator lens 200 provided in this embodiment are shown in table 3.

TABLE 3 Table 3

The surface profile coefficients of the aspherical surfaces of the collimator lens 200 in this embodiment are shown in table 4.

TABLE 4 Table 4

In this embodiment, schematic diagrams of curvature of field, distortion and imaging collimation of the collimator lens 200 are shown in fig. 6, 7 and 8, respectively.

Third embodiment

Referring to fig. 9, the collimating lens 300 of the present embodiment is substantially the same as the collimating lens 100 of the first embodiment in terms of structure, except that the object-side surface of the third lens element of the collimating lens 300 is a concave surface.

The relevant parameters of each lens in the collimator lens 300 provided in this embodiment are shown in table 5.

TABLE 5

The surface profile coefficients of the aspherical surfaces of the collimator lens 300 in this embodiment are shown in table 6.

TABLE 6

In this embodiment, schematic diagrams of curvature of field, distortion and imaging collimation of the collimator lens 300 are shown in fig. 10, 11 and 12, respectively.

Table 7 is an optical characteristic corresponding to the above three embodiments, and mainly includes an effective focal length f, an optical total length TTL, a numerical aperture NA, and an object height OH, and a numerical value corresponding to each of the above conditional expressions.

TABLE 7

The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.

Claims

1. The utility model provides a collimating lens which characterized in that includes from laser emitter end to the measured object end in proper order:

a first lens with positive focal power, wherein the object side surface of the first lens is a convex surface, and the image side surface of the first lens is a concave surface;

a second lens with negative focal power, wherein the object side surface of the second lens is a concave surface, and the image side surface of the second lens is a convex surface;

a third lens having positive optical power, an image side surface of the third lens being a convex surface;

a diaphragm;

the laser emitter end is an object side, the object end to be measured is an image side, the first lens and the second lens are made of plastic materials, and the third lens is made of glass materials.

2. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

1.5＜Nd1＜1.6；

1.5＜Nd2＜1.6；

1.6＜Nd3＜1.7；

wherein Nd1 represents a material refractive index of the first lens, nd2 represents a material refractive index of the second lens, and Nd3 represents a material refractive index of the third lens.

3. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

(dn/dt) ₁ ×TCE ₁ ×f ₁ ＞-40×10 ^-3 mm/℃ ² ；

(dn/dt) ₂ ×TCE ₂ ×f ₂ ＜40×10 ^-3 mm/℃ ² ；

(dn/dt) ₃ ×TCE ₃ ×f ₃ ＞-1×10 ^-3 mm/℃ ² ；

wherein, (dn/dt) ₁ Indicating the temperature coefficient of refractive index, TCE, of the first lens in the range of 0-60 DEG C ₁ Representing the coefficient of thermal expansion, f, of the first lens ₁ Representing the focal length of the first lens at normal temperature (20 ℃); (dn/dt) ₂ Indicating the temperature coefficient of refractive index, TCE, of the second lens in the range of 0-60 DEG C ₂ Representing the coefficient of thermal expansion, f, of the second lens ₂ Represents the focal length of the second lens at normal temperature (20 ℃); (dn/dt) ₃ Indicating the temperature coefficient of refractive index, TCE, of the third lens in the range of 0-60 DEG C ₃ Representing the coefficient of thermal expansion, f, of the third lens ₃ The focal length of the third lens at normal temperature (20 ℃ C.) is shown.

4. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

3.5＜f1/r1＜4.5；

wherein f1 represents a focal length of the first lens, and r1 represents a radius of curvature of the object side surface of the first lens.

5. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

-0.5＜r1/r6＜-0.3；

where r1 represents a radius of curvature of the first lens object-side surface, and r6 represents a radius of curvature of the third lens image-side surface.

6. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

-3＜f/r6＜-2；

where f represents a system focal length of the collimating lens, and r6 represents a radius of curvature of the image side surface of the third lens.

7. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

-2.0<r2/r4<-0.3；

-0.2<r3/r5<0.02；

wherein r2 represents a radius of curvature of the image side surface of the first lens, r3 represents a radius of curvature of the object side surface of the second lens, r4 represents a radius of curvature of the image side surface of the second lens, and r5 represents a radius of curvature of the object side surface of the third lens.

8. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

-2<f3/f2<0；

wherein f2 represents the focal length of the second lens, and f3 represents the focal length of the third lens.

9. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

0.4＜CT1/CT2＜1.1；

wherein CT1 represents the center thickness of the first lens and CT2 represents the center thickness of the second lens.

10. The collimator lens of claim 1, wherein the collimator lens satisfies the following conditional expression:

0＜(CT1+CT3)/CT2＜2；

wherein CT1 represents the center thickness of the first lens, CT2 represents the center thickness of the second lens, and CT3 represents the center thickness of the third lens.