Collimating lens

Abstract

The present invention discloses a collimating lens, which comprises, from the laser emitter end to the measured object end, a first lens with positive optical power, whose object side surface is convex and whose image side surface is concave; a second lens with negative optical power, whose object side surface is concave and whose image side surface is convex; a third lens with positive optical power, whose image side surface is convex; and an aperture; wherein the aperture is located between the third lens and the measured object; the first lens and the second lens are made of plastic, and the third lens is made of molded glass. The collimating lens provided by the present invention adopts three lenses and sets a specific surface shape and optical power for each lens. It can not only effectively utilize lenses with different refractive indices and focal lengths to achieve clear imaging, but also can perform collimated projection through each lens, ensuring that the collimating lens has less distortion and that the overall performance of the collimating lens varies less under different temperatures, thereby achieving the purpose of enhancing the focal length stability of the collimating lens.

Description

Technical Field

[0001] The present invention relates to the technical field of camera lenses, in particular to a collimating lens. Background Art

[0002] In recent years, 3D photography technology has developed rapidly. This optical sensing technology based on 3D structured light can be used for face recognition, gesture recognition, enhanced photography functions, and new applications of AR. It can transform optical images from the past two-dimensional space into three-dimensional space, making the user experience more real and clear.

[0003] 3D structured light involves projecting specific laser information onto the surface of an object, which is captured by a camera. The changes in light information caused by the object are then used to calculate the object's position and depth, thereby restoring the entire three-dimensional space. Specific laser information is a crucial metric in 3D structured light technology, so projecting this laser information onto the surface of the object being measured is extremely demanding. The collimating lens, which projects an array of point light sources emitted at specific solid angles from a VCSEL (Vertical Cavity Surface Emitting Laser) laser onto the surface of the object being measured, is a key component of 3D imaging quality.

[0004] In existing products of this type, the focal length f of the lens varies significantly with ambient temperature, causing significant shifts in the angle of the light projected by the lens. This, in turn, alters the original light information, leading to errors in the calculations of the entire system and affecting the accuracy of 3D object contour recovery. Similarly, the collimation decreases with temperature, which also reduces the clarity of the 3D object recovered by the system. Therefore, it is particularly important to maintain a stable lens focal length to prevent significant changes in the field of view angle and collimation of the light information projected onto the object being measured when the ambient temperature fluctuates. Summary of the Invention

[0005] Therefore, an object of the present invention is to provide a collimating lens to ensure that the field angle and collimation of light information projected onto the object under test do not change significantly under different temperature conditions.

[0006] The embodiments of the present invention implement the above-mentioned invention objectives through the following technical solutions.

[0007] The present invention provides a collimating lens, which comprises three lenses in total, and includes, from the laser emitter end to the measured object end, a first lens with positive optical power, whose object side surface is convex and whose image side surface is concave; a second lens with negative optical power, whose object side surface is concave and whose image side surface is convex; a third lens with positive optical power, whose image side surface is convex; and an aperture; wherein the laser emitter end is the object side, the measured object end is the image side, the first lens and the second lens are made of plastic, and the third lens is made of glass.

[0008] Compared with the prior art, the collimating lens provided by the present invention, by setting a first lens, a second lens, and a third lens, and setting a specific surface shape and optical focal length for each lens, can not only effectively utilize lenses with different refractive indices and focal lengths to achieve clear imaging, but also can perform collimated projection through each lens, ensuring that the collimating lens has less distortion, while ensuring that the overall performance of the collimating lens at different temperatures changes little, enhancing the focal length stability of the collimating lens, and achieving the purpose of not significantly changing the field of view angle and collimation of the light information projected onto the object under test under different temperature conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the following description of the embodiments with reference to the accompanying drawings.

[0010] Figure 1 FIG. 4 is a schematic structural diagram of a collimating lens according to a first embodiment of the present invention.

[0011] Figure 2 FIG. 4 is a field curvature curve diagram of the collimating lens according to the first embodiment of the present invention.

[0012] Figure 3 FIG. 4 is a distortion curve diagram of the collimating lens according to the first embodiment of the present invention.

[0013] Figure 4 FIG. 1 is a schematic diagram of the imaging collimation of the collimating lens according to the first embodiment of the present invention.

[0014] Figure 5 FIG. 4 is a schematic structural diagram of a collimating lens according to a second embodiment of the present invention.

[0015] Figure 6 FIG. 4 is a field curvature curve diagram of the collimating lens according to the second embodiment of the present invention.

[0016] Figure 7 FIG. 4 is a distortion curve diagram of the collimating lens according to the second embodiment of the present invention.

[0017] Figure 8 FIG. 4 is a schematic diagram of the imaging collimation of the collimating lens according to the second embodiment of the present invention.

[0018] Figure 9 FIG. 4 is a schematic structural diagram of a collimating lens according to a third embodiment of the present invention.

[0019] Figure 10 FIG. 4 is a field curvature curve diagram of the collimating lens according to the third embodiment of the present invention.

[0020] Figure 11 FIG. 4 is a distortion curve diagram of the collimating lens according to the third embodiment of the present invention.

[0021] Figure 12FIG. 4 is a schematic diagram of the imaging collimation of the collimating lens according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0022] To make the objects, features, and advantages of the present invention more readily apparent, the following detailed description of specific embodiments of the present invention is provided in conjunction with the accompanying drawings. The accompanying drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0024] An embodiment of the present invention proposes a collimating lens, which includes, from the laser emitter end to the object to be measured, in sequence: a first lens, a second lens, a third lens and an aperture, and the optical centers of each lens are located on the same straight line; wherein, the laser emitter end is the object side, the object to be measured end is the image side, the first lens and the second lens are made of plastic, and the third lens is made of glass.

[0025] Specifically, the first lens has positive focal power, its object side surface is convex and its image side surface is concave; the second lens has negative focal power, its object side surface is concave and its image side surface is convex; the third lens has positive focal power, its image side surface is convex; the first lens, the second lens and the third lens are all aspherical lenses; the aperture is close to the end of the object to be measured.

[0026] The present invention provides a first lens, a second lens, and a third lens, and sets a specific surface shape and optical focal length for each lens. This not only effectively utilizes lenses with different refractive indices and focal lengths to achieve clear imaging, but also enables collimated projection through each lens, thereby ensuring that the collimating lens has minimal distortion and that the overall performance of the collimating lens varies minimally at different temperatures, thereby enhancing the focal length stability of the collimating lens, and achieving the goal of maintaining a significant change in the field angle and collimation of light information projected onto the object under test under different temperature conditions.

[0027] In some embodiments, the collimating lens satisfies the following conditional formula:

[0028] 1.5<Nd1<1.6;(1)

[0029] 1.5<Nd2<1.6;(2)

[0030] 1.6<Nd3<1.7;(3)

[0031] Wherein, Nd1 represents the refractive index of the material of the first lens, Nd2 represents the refractive index of the material of the second lens, and Nd3 represents the refractive index of the material of the third lens. Satisfying the above-mentioned conditional equations (1), (2), and (3) and rationally matching the refractive indices of the lens materials is beneficial for correcting the aberration of the collimating lens and improving the imaging quality of the collimating lens.

[0032] In some embodiments, the collimating lens satisfies the following conditional formula:

[0033] (dn / dt)1×TCE1×f1>-40×10 -3 mm / ℃ 2 ;(4)

[0034] (dn / dt)2×TCE2×f2<40×10 -3 mm / ℃ 2 ; (5)

[0035] (dn / dt)3×TCE3×f3>-1×10 -3 mm / ℃ 2 ; (6)

[0036] Wherein, (dn / dt)1 represents the temperature coefficient of the refractive index of the first lens in the range of 0 to 60°C, TCE1 represents the thermal expansion coefficient of the first lens, and f1 represents the focal length of the first lens at room temperature (20°C); (dn / dt)2 represents the temperature coefficient of the refractive index of the second lens in the range of 0 to 60°C, TCE2 represents the thermal expansion coefficient of the second lens, and f2 represents the focal length of the second lens at room temperature (20°C); (dn / dt)3 represents the temperature coefficient of the refractive index of the third lens in the range of 0 to 60°C, TCE3 represents the thermal expansion coefficient of the third lens, and f3 represents the focal length of the third lens at room temperature (20°C). Satisfying the above-mentioned conditional equations (4), (5), and (6) clearly limits the rate of change of the refractive index of each lens with temperature, and reasonably matches the different thermal expansion characteristics of the lens materials, thereby achieving the stability of the focal length of the entire system and ensuring the collimation effect of the lens, thereby restoring the entire three-dimensional space under different temperature conditions without changing the original light information.

[0037] In some embodiments, the collimating lens satisfies the following conditional formula:

[0038] 3.5<f1 / r1<4.5;(7)

[0039] Wherein, f1 represents the focal length of the first lens, and r1 represents the radius of curvature of the object side of the first lens. Satisfying the above conditional equation (7) can limit the shape of the object side of the first lens of the collimating lens, which is beneficial to the processing and manufacturing of the lens and can also reduce tolerance sensitivity.

[0040] In some embodiments, the collimating lens satisfies the following conditional formula:

[0041] -0.5<r1 / r6<-0.3;(8)

[0042] Where r1 represents the radius of curvature of the object side of the first lens, and r6 represents the radius of curvature of the image side of the third lens. Satisfying the above conditional equation (8) can limit the orientation of the object side of the first lens and the image side of the third lens of the collimating lens to opposite directions, thereby converging the light passing through the third lens onto the imaging surface and improving the collimation effect of the lens.

[0043] In some embodiments, the collimating lens satisfies the following conditional formula:

[0044] -3<f / r6<-2;(9)

[0045] Wherein, f represents the system focal length of the collimating lens, and r6 represents the radius of curvature of the image side surface of the third lens. Satisfying the above conditional equation (9) can limit the shape of the image side surface of the third lens, which is beneficial to lens processing and can reduce tolerance sensitivity.

[0046] In some embodiments, the collimating lens satisfies the following conditional formula:

[0047] -2.0 <r2 / r4<-0.3;(10)

[0048] -0.2 <r3 / r5<0.02;(11)

[0049] Wherein, r2 represents the radius of curvature of the image side surface of the first lens, r3 represents the radius of curvature of the object side surface of the second lens, r4 represents the radius of curvature of the image side surface of the second lens, and r5 represents the radius of curvature of the object side surface of the third lens. Satisfying the above conditional equations (10) and (11) can effectively control the shapes of the image side surfaces of the first and second lenses, as well as the shapes of the object side surfaces of the second and third lenses, thereby reducing the aberrations of the collimating lens, balancing the field curvature, and thus improving the imaging quality of the collimating lens.

[0050] In some embodiments, the collimating lens satisfies the following conditional formula:

[0051] -2 <f3 / f2<0; (12)

[0052] Wherein, f2 represents the focal length of the second lens, and f3 represents the focal length of the third lens. Satisfying the above conditional equation (12) can effectively limit the optical power ratio of the second lens and the third lens, reduce the aberration of the collimating lens, and improve the imaging quality.

[0053] In some embodiments, the collimating lens satisfies the following conditional formula:

[0054] TTL / f<0.85; (13)

[0055] Wherein, TTL represents the total optical length of the collimating lens, and f represents the system focal length of the collimating lens. Satisfying the above conditional equation (13) can limit the ratio between the total system length and the system focal length, achieving a balance between the system's long focal length and miniaturization. Specifically, the total optical length TTL of the collimating lens can be limited to less than 6.2 mm, and the system focal length f of the collimating lens can be greater than 6.5 mm, which is conducive to ensuring better optical properties and is also suitable for the implementation of 3D structured light algorithms.

[0056] In some embodiments, the collimating lens satisfies the following conditional formula:

[0057] 0.4<CT1 / CT2<1.1; (14)

[0058] Where CT1 represents the center thickness of the first lens, and CT2 represents the center thickness of the second lens. Satisfying the above conditional equation (14) limits the ratio of the center thickness of the second lens to the center thickness of the first lens of the collimating lens. By properly configuring the center thickness of the lenses, the processing, manufacturing, and assembly of the optical lens assembly are facilitated.

[0059] In some embodiments, the collimating lens satisfies the following conditional formula:

[0060] 0<(CT1+CT3) / CT2<2;(15)

[0061] Where 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 equation (15) helps expand the beam width, while ensuring the uniformity of the infrared beam emitted by the laser transmitter and improving the collimation effect of the lens.

[0062] The present invention is further described below using multiple embodiments. In each embodiment, the thickness and radius of curvature of the individual lenses in the collimating lens vary; for details, please refer to the parameter tables of each embodiment. The following embodiments are merely preferred embodiments of the present invention, but the present invention is not limited to these embodiments. Any other changes, substitutions, combinations, or simplifications that do not deviate from the novelties of the present invention shall be considered equivalent replacements and are included within the scope of protection of the present invention.

[0063] In various embodiments of the present invention, the aspheric surface of each lens satisfies the following equation:

[0064]

[0065] Among them, z is the distance vector height from the vertex of the aspheric surface when the aspheric surface is at a height of h along the optical axis, c is the paraxial curvature of the surface, k is the quadratic surface coefficient, and A 2i is the 2i-th order aspheric surface coefficient.

[0066] First embodiment

[0067] See also Figure 1 , shown is a schematic structural diagram of a collimating lens 100 provided in a first embodiment of the present invention. The collimating lens 100 comprises, in order from the object side to the imaging surface S7 along the near optical axis: a first lens L1, a second lens L2, a third lens L3, and an aperture ST. Specifically, the first lens L1 has positive focal power, with its object-side surface S1 being convex and its image-side surface S2 being concave; the second lens L2 has negative focal power, with its object-side surface S3 being concave and its image-side surface S4 being convex; and the third lens L3 has positive focal power, with its object-side surface S5 being convex at the near optical axis and its image-side surface S6 being convex. The first and second lenses L1 and L2 are plastic aspherical lenses, while the third lens L3 is a molded glass aspherical lens.

[0068] Table 1 shows the parameters of the lenses in the collimating lens 100 provided in this embodiment.

[0069] Table 1

[0070]

[0071] Table 2 shows the surface coefficients of the aspheric surfaces of the collimating lens 100 in this embodiment.

[0072] Table 2

[0073]

[0074] In this embodiment, the field curvature, distortion, and imaging collimation diagrams of the collimating lens 100 are shown as follows: Figure 2 、 Figure 3 、 Figure 4 shown.

[0075] Second embodiment

[0076] The structural diagram of the collimating lens 200 provided in this embodiment can be found in Figure 5 The collimating lens 200 in this embodiment has substantially the same structure as the collimating lens 100 in the first embodiment, except that the object-side surface of the third lens element of the collimating lens 200 is concave.

[0077] Table 3 shows the parameters of each lens in the collimating lens 200 provided in this embodiment.

[0078] Table 3

[0079]

[0080] The surface coefficients of the aspheric surfaces of the collimating lens 200 in this embodiment are shown in Table 4.

[0081] Table 4

[0082]

[0083] In this embodiment, the field curvature, distortion, and imaging collimation diagrams of the collimating lens 200 are shown as follows: Figure 6 、 Figure 7 、 Figure 8 shown.

[0084] Third embodiment

[0085] The structural diagram of the collimating lens 300 provided in this embodiment can be found in Figure 9 The structure of the collimating lens 300 in this embodiment is substantially the same as that of the collimating lens 100 in the first embodiment, except that the object-side surface of the third lens of the collimating lens 300 is concave.

[0086] Table 5 shows the parameters of the lenses in the collimating lens 300 provided in this embodiment.

[0087] Table 5

[0088]

[0089] The surface coefficients of the aspheric surfaces of the collimating lens 300 in this embodiment are shown in Table 6.

[0090] Table 6

[0091]

[0092] In this embodiment, the field curvature, distortion, and imaging collimation diagrams of the collimating lens 300 are shown as follows: Figure 10 、 Figure 11 、 Figure 12 shown.

[0093] Table 7 shows the optical characteristics corresponding to the above three embodiments, mainly including the effective focal length f, the total optical length TTL, the numerical aperture NA and the object height OH, as well as the values ​​corresponding to each of the above conditional expressions.

[0094] Table 7

[0095]

[0096]

[0097] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A collimating lens, characterized in that: From the laser transmitter end to the object under test, it includes: a first lens having positive refractive power, wherein the object-side surface of the first lens is convex and the image-side surface of the first lens is concave; a second lens having negative optical power, wherein the object-side surface of the second lens is concave and the image-side surface of the second lens is convex; a third lens having positive refractive power, wherein the image-side surface of the third lens is convex; Aperture; The laser emitter end is the object side, the measured object end is the image side, the first lens and the second lens are made of plastic, and the third lens is made of glass; The collimating lens satisfies the following conditional formula: -0.5＜r1 / r6＜-0.3； Wherein, r1 represents the curvature radius of the object side of the first lens, and r6 represents the curvature radius of the image side of the third lens.

2. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: 1.5<Nd1<1.6; 1.5<Nd2<1.6; 1.6<Nd3<1.7; Wherein, Nd1 represents the refractive index of the material of the first lens, Nd2 represents the refractive index of the material of the second lens, and Nd3 represents the refractive index of the material of the third lens.

3. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: (dn / dt)1×TCE1×f1>-40×10 -3 mm / ℃ 2 ; (dn / dt)2×TCE2×f2<40×10 -3 mm / ℃ 2 ; (dn / dt)3×TCE3×f3>-1×10 -3 mm / ℃ 2 ; Wherein, (dn / dt)1 represents the temperature coefficient of the refractive index of the first lens in the range of 0 to 60°C, TCE1 represents the thermal expansion coefficient of the first lens, and f1 represents the focal length of the first lens at a room temperature of 20°C; (dn / dt)2 represents the temperature coefficient of the refractive index of the second lens in the range of 0 to 60°C, TCE2 represents the thermal expansion coefficient of the second lens, and f2 represents the focal length of the second lens at a room temperature of 20°C; (dn / dt)3 represents the temperature coefficient of the refractive index of the third lens in the range of 0 to 60°C, TCE3 represents the thermal expansion coefficient of the third lens, and f3 represents the focal length of the third lens at a room temperature of 20°C.

4. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: 3.5＜f1 / r1＜4.5； Wherein, f1 represents the focal length of the first lens, and r1 represents the curvature radius of the object side of the first lens.

5. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: TTL / f<0.85; Wherein, TTL represents the total optical length of the collimating lens, and f represents the system focal length of the collimating lens.

6. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: -3＜f / r6＜-2； Wherein, f represents the system focal length of the collimating lens, and r6 represents the curvature radius of the image side surface of the third lens.

7. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: -2.0<r2 / r4<-0.3； -0.2<r3 / r5<0.02； Among them, r2 represents the curvature radius of the image side of the first lens, r3 represents the curvature radius of the object side of the second lens, r4 represents the curvature radius of the image side of the second lens, and r5 represents the curvature radius of the object side of the third lens.

8. The collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: -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 collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: 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 collimating lens according to claim 1, wherein: The collimating lens satisfies the following conditional formula: 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.

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