WO2019169683A1 - 准直镜头 - Google Patents

准直镜头 Download PDF

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Publication number
WO2019169683A1
WO2019169683A1 PCT/CN2018/081611 CN2018081611W WO2019169683A1 WO 2019169683 A1 WO2019169683 A1 WO 2019169683A1 CN 2018081611 W CN2018081611 W CN 2018081611W WO 2019169683 A1 WO2019169683 A1 WO 2019169683A1
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Prior art keywords
lens
collimating lens
collimating
focal length
order
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PCT/CN2018/081611
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English (en)
French (fr)
Inventor
刘绪明
曾昊杰
曾吉勇
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江西联益光学有限公司
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Priority to US16/326,377 priority Critical patent/US11163173B2/en
Publication of WO2019169683A1 publication Critical patent/WO2019169683A1/zh

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/001—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras
    • G02B13/0015—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design
    • G02B13/002—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface
    • G02B13/0035—Miniaturised objectives for electronic devices, e.g. portable telephones, webcams, PDAs, small digital cameras characterised by the lens design having at least one aspherical surface having three lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/30—Collimators
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0004—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed
    • G02B19/0009—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only
    • G02B19/0014—Condensers, e.g. light collectors or similar non-imaging optics characterised by the optical means employed having refractive surfaces only at least one surface having optical power
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B19/00—Condensers, e.g. light collectors or similar non-imaging optics
    • G02B19/0033—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use
    • G02B19/0047—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source
    • G02B19/0052—Condensers, e.g. light collectors or similar non-imaging optics characterised by the use for use with a light source the light source comprising a laser diode
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B3/00—Simple or compound lenses
    • G02B3/02—Simple or compound lenses with non-spherical faces
    • G02B3/04—Simple or compound lenses with non-spherical faces with continuous faces that are rotationally symmetrical but deviate from a true sphere, e.g. so called "aspheric" lenses
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N13/00—Stereoscopic video systems; Multi-view video systems; Details thereof
    • H04N13/20—Image signal generators
    • H04N13/204—Image signal generators using stereoscopic image cameras

Definitions

  • the present invention relates to the field of camera lens technology, and in particular to a collimating lens.
  • This 3D structured light-based optical sensing technology can be used for face recognition, gesture recognition, and enhancement.
  • the camera function brings new applications of AR, transforming optical images from the past two-dimensional to three-dimensional space, resulting in a more realistic and clear perception experience.
  • 3D structured light refers to the information collected by the camera after the specific laser information is projected onto the surface of the object, and the information such as the position and depth of the object is calculated according to the change of the optical information caused by the object, thereby restoring the entire three-dimensional space.
  • Specific laser information is a very important indicator in 3D structured light technology, so it is very demanding for collimating lenses that project laser information onto the surface of the object being measured.
  • This type of collimating lens that projects an array point source with a specific solid angle emission on the surface of a VCSEL (Vertical Cavity Surface Emitting Laser) laser to the surface of the object to be measured is a key component of 3D imaging quality.
  • VCSEL Very Cavity Surface Emitting Laser
  • the first lens of the conventional collimating lens close to the laser emitter is a plastic lens, which is easy to age; and the reliability test of such a lens is difficult to pass.
  • the present invention aims to solve at least one of the technical problems existing in the prior art. Accordingly, it is an object of the present invention to provide a collimating lens that has a stable focal length at different temperatures and is more reliable.
  • the laser emitter end to the object end to be tested includes:
  • a second lens having a negative power, the object side surface being a concave surface
  • the image side surface is convex
  • optical centers of the respective lenses are on the same straight line
  • the collimating lens satisfies the following conditional formula:
  • the laser emitter end is the object side
  • the measured object end is the image side
  • f1 represents the focal length of the first lens
  • f23 represents the combined focal length of the second lens and the third lens
  • Dn/dt)1, (dn/dt)2, and (dn/dt)3 respectively indicate that the refractive indices of the first lens, the second lens, and the third lens are in a range of 0 to 60 ° C with temperature Rate of change.
  • the collimating lens has a reasonable distribution of the refractive index of each lens with temperature, and can be offset by the influence of the thermal expansion focal length of the lens itself and the structural member, so that the focal length can be stabilized and suitable for different temperature occasions. .
  • the effective focal length variation of the collimating lens can be less than 0.001 mm for every 10 °C change in temperature, so that the angle of the projected light of the lens does not change significantly, and the original optical information is not changed.
  • the first lens can effectively delay the aging of the lens, the reliability is stronger, the reliability test is easier, and the test result is stable.
  • the collimating lens satisfies the conditional expression:
  • TTL represents the total optical length of the collimating lens
  • f represents the focal length of the system of the collimating lens
  • the collimating lens satisfies the conditional expression:
  • f3 represents the focal length of the third lens
  • f1 represents the focal length of the first lens
  • the collimating lens satisfies the conditional expression:
  • f denotes the focal length of the system of the collimating lens
  • r1 denotes the radius of curvature of the surface of the first lens object
  • the collimating lens satisfies the conditional expression:
  • r1 represents a radius of curvature of the first lens object side surface
  • r6 represents a radius of curvature of the third lens image side surface
  • the collimating lens satisfies the conditional expression:
  • CT1 represents the center thickness of the first lens
  • CT3 represents the center thickness of the third lens
  • each of the object side surface and the image side surface of the first lens, the second lens, and the third lens are aspherical.
  • the first lens is made of glass
  • the second lens and the third lens are made of plastic material.
  • z is the distance of the surface away from the vertex of the surface in the direction of the optical axis
  • c is the curvature of the vertex of the surface
  • k is the quadric surface coefficient
  • h is the distance from the optical axis to the surface
  • B, C, D, E, F, G, H represents the fourth-order, sixth-order, eighth-order, ten-order, twelve-order, fourteenth-order, and sixteenth-order surface coefficients, respectively.
  • FIG. 1 is a schematic cross-sectional view of a collimating lens according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of an optical circuit of a laser emitter emitted through the collimating lens of FIG. 1;
  • FIG. 3a is a field curve diagram of a collimating lens in Embodiment 1 of the present invention when imaged at 40 ° C and 300 mm image distance, in which the x-axis is a field curvature value, the coordinate unit is mm, and the y-axis is defined by the object height.
  • 3b is a distortion diagram of the collimating lens in Embodiment 1 of the present invention at 40° C. and 300 mm image distance, in which the x-axis is a distortion value, the coordinate unit is a percentage, and the y-axis is a field of view defined by the object height. ;
  • FIG. 4 is a schematic view showing the size and shape of a pixel of a collimating lens according to Embodiment 1 of the present invention at 40° C. and 300 mm image distance, in units of micrometers;
  • Figure 5a is a graph of field curvature of a collimating lens in Embodiment 2 of the present invention at 40 ° C, 300 mm image distance;
  • Figure 5b is a distortion diagram of the collimating lens in Embodiment 2 of the present invention at 40 ° C, 300 mm image distance imaging;
  • FIG. 6 is a schematic view showing the size and shape of a pixel of a collimating lens according to Embodiment 2 of the present invention at 40° C. and 300 mm image distance, in units of micrometers;
  • FIG. 7a is a field curve diagram of a collimating lens in Embodiment 3 of the present invention when imaged at 40 ° C and 300 mm image distance;
  • FIG. 7b is a distortion diagram of the collimating lens in Embodiment 3 of the present invention when imaged at 40 ° C and 300 mm image distance;
  • FIG. 8 is a schematic view showing the size and shape of a pixel of a collimating lens according to Embodiment 3 of the present invention at 40° C. and 300 mm image distance, in units of micrometers;
  • Figure 9a is a graph of field curvature of a collimating lens in Embodiment 4 of the present invention at 40 ° C, 300 mm image distance;
  • Figure 9b is a distortion diagram of the collimating lens in Embodiment 4 of the present invention when imaged at 40 ° C and 300 mm image distance;
  • FIG. 10 is a schematic view showing the size and shape of a pixel of a collimating lens according to Embodiment 4 of the present invention at 40° C. and 300 mm image distance, in units of micrometers;
  • Figure 11 is a cross-sectional structural view showing a collimating lens according to Embodiment 5 of the present invention.
  • Figure 12a is a graph of field curvature of a collimating lens in Embodiment 5 of the present invention when imaged at 40 ° C and 300 mm image distance;
  • Figure 12b is a distortion diagram of the collimating lens in Embodiment 5 of the present invention at 40 ° C, 300 mm image distance imaging;
  • FIG. 13 is a schematic view showing the size and shape of a pixel of a collimating lens according to Embodiment 5 of the present invention at 40° C. and 300 mm image distance, and the unit is micrometer.
  • a collimating lens 10 includes a first lens L1 adjacent to a laser emitter 20 (ie, an object side) and having a positive power, and a second lens having a negative power.
  • L2 a third lens L3 having positive refractive power, close to the pupil S7 of the object to be measured (that is, the image side); and the optical centers of the respective lenses are on the same straight line.
  • the first lens L1 has positive refractive power, and the object side surface thereof is convex, thereby concentrating the telecentric beam from the laser, and providing sufficient positive power with the first lens L1, can effectively control the whole of the optical lens group. volume.
  • the second lens L2 has a negative refractive power, and the object side surface is a concave surface, which can effectively adjust the aberration generated by the first lens L1, and can also control the focusing ability of the working wavelength band.
  • the third lens L3 has positive refractive power, and the image side surface is convex, which can effectively correct the aberration of the optical lens, and can effectively control the exit angle.
  • the object side surface and the image side surface of the first lens L1, the second lens L2, and the third lens L3 are aspherical surfaces, that is, the object side surfaces of the first lens L1, the second lens L2, and the third lens L3, and
  • the image side surface is formed into a shape other than a spherical surface, whereby a large number of control variables can be obtained to reduce aberrations.
  • the collimating lens 10 provided by the present embodiment satisfies the following conditional expression:
  • f1 represents the focal length of the first lens
  • f23 represents the combined focal length of the second lens and the third lens
  • (dn/dt)1, (dn/dt)2 and (dn/dt)3 represent the first lens, respectively
  • the refractive index of the two lenses and the third lens varies with temperature in the range of 0 to 60 °C.
  • the focal length of the system can be larger and the angle of view is smaller, which is more advantageous for the algorithm implementation of 3D structured light.
  • FIG. 2 is a schematic diagram of an optical circuit of the emitted light 30 of the laser emitter 20 passing through the collimating lens 10 .
  • the first lens L1 of the laser emitter end 20 is adjacent.
  • the refractive index in the range of 0 to 60 ° C with temperature changes to (dn / dt) 1 > -10 ⁇ 10 -6 / ° C, the first lens with the material characteristics, that is, the glass lens, due to the laser
  • the emitter is a light source, and the first lens close to the light source is made of glass, which can effectively delay the aging of the lens, is more reliable, and is easier to pass the reliability test, and the test result is stable.
  • the second lens L2 and the third lens L3 which are far away from the light source may be made of a plastic material, thereby effectively reducing the production cost.
  • the difference between the focal length f1 of the first lens L1 and the combined focal length f23 of the second lens L2 and the third lens L3 is less than 0, and the condition f1 ⁇ f23 is satisfied, which limits the condition
  • the combination of the two lenses L2 and the third lens L3 is weaker in the ability to deflect light than the first lens L1.
  • the refractive indices of the first lens L1, the second lens L2, and the third lens L3 in the range of 0 to 60 ° C vary with temperature (dn/dt) 1, (dn/dt) 2, and (dn /dt)3 satisfies the condition (dn/dt)1>-10 ⁇ 10 -6 /°C, (dn/dt)2 ⁇ -50 ⁇ 10 -6 /°C, (dn/dt)3 ⁇ -50 ⁇ 10 - 6 / ° C.
  • This condition limits the rate of change of the refractive index of the three lenses with temperature, and is mainly used to reasonably match the thermal expansion of the lens to ensure the stability of the lens focal length at different temperatures.
  • the optical total length TTL of the collimating lens 10 and the system focal length f satisfy the conditional formula: TTL/f ⁇ 1.0, which limits the proportional relationship between the total length of the system and the focal length of the system, and can ensure the long focal length of the system. Achieve the purpose of system miniaturization.
  • the optical total length TTL of the collimating lens 10 is less than 3.5 mm, and the focal length f of the collimating lens 10 is greater than 3.5 mm to ensure better optical characteristics, and is more suitable for 3D structured light algorithms. achieve.
  • a focal length f3 of the third lens L3 has a ratio of a focal length f1 of the first lens L1 of a range of 0 ⁇ f3/f1 ⁇ 5. This condition limits the ratio of the first lens L1 to the third lens L3, and is mainly used to concentrate the light passing through the third lens L3 on the imaging surface while reducing the aberration of the collimating lens.
  • the ratio of the focal length f of the collimating lens 10 to the radius of curvature r1 of the object side surface of the first lens L1 is: 0 ⁇ f/r1 ⁇ 10, which limits the shape of the side surface of the first lens L1 It is beneficial to the processing of the lens and can reduce the tolerance sensitivity.
  • a ratio of a radius of curvature r1 of the object side surface of the first lens L1 to a radius of curvature r6 of the image side surface of the third lens L3 is ⁇ 10 ⁇ r1/r6 ⁇ 0. This condition restricts the opposite direction of the object side surface of the first lens L1 from the image side surface of the third lens side L3, and is mainly used for concentrating light passing through the third lens L3 on the imaging surface while reducing the standard Straight lens aberration.
  • a ratio of a center thickness CT3 of the third lens L3 to a center thickness CT1 of the first lens L1 is: 0 ⁇ CT3/CT1 ⁇ 5, which limits the center thickness of the third lens L3 and the first
  • the ratio of the center thickness of a lens L1 facilitates the fabrication and assembly of the optical lens group by appropriately arranging the center thickness of the lens.
  • each of the object side surface and the image side surface of the first lens L1, the second lens L2, and the third lens L3 are aspherical, thereby obtaining more control variables to reduce the image difference.
  • the collimating lens 10 is smaller in size, capable of achieving stable focal length and being suitable for different temperature applications.
  • the refractive index of each lens is distributed reasonably with the rate of change of temperature and the coefficient of thermal expansion, so that the angle of the projected light of the lens does not change significantly, and the original optical information is not changed; and under the same size VCSEL (laser emitter),
  • the realization of the system's focal length is larger, the field of view angle is smaller, which is more conducive to the algorithm implementation of 3D structured light.
  • the first lens L1 near the laser emitter is made of glass, which can effectively delay the aging of the lens; and pass the reliability test, and the test result is stable.
  • the thickness and the radius of curvature of the respective lenses in the collimating lens are different.
  • the following embodiments are merely preferred embodiments of the present invention, but the embodiments of the present invention are not limited by the following embodiments, and any other changes, substitutions, combinations or simplifications that do not depart from the innovation of the present invention, All should be considered as equivalent replacement means, and are included in the scope of protection of the present invention.
  • r represents the radius of curvature of the apex of the optical surface
  • d represents the optical surface spacing (distance between the apexes of two adjacent optical surfaces)
  • nd represents the refractive index of each lens
  • Vd represents each lens.
  • Abbe number used to measure the degree of light dispersion of the medium.
  • z is the distance of the surface away from the vertex of the surface in the direction of the optical axis
  • c is the curvature of the vertex of the surface
  • k is the quadric surface coefficient
  • h is the distance from the optical axis to the surface
  • B, C, D, E, F, G, H represents the fourth-order, sixth-order, eighth-order, ten-order, twelve-order, fourteenth-order, and sixteenth-order surface coefficients, respectively.
  • the thickness and the radius of curvature of each lens in the collimating lens are different. For specific differences, refer to the parameter table of each embodiment.
  • the second lens L2 is an aspherical lens having a concave surface on the object side surface and a convex surface on the image side surface.
  • FIG. 3a, 3b and FIG. 4 respectively show the optical characteristic curves of the collimating lens in this embodiment.
  • the relevant parameters of each lens in the collimating lens in this embodiment are shown in Table 1-1.
  • the schematic diagram of the cross-sectional structure of the collimating lens provided in the second embodiment of the present invention is substantially the same as that of the first embodiment, and details are not described herein. Please refer to FIG. 5a, FIG. 5b and FIG.
  • the optical characteristic curve of the straight lens The relevant parameters of each lens in the collimating lens of this embodiment are shown in Table 2-1.
  • the schematic diagram of the cross-sectional structure of the collimating lens provided in the third embodiment of the present invention is substantially the same as that of the first embodiment, and details are not described herein. Please refer to FIG. 7a, FIG. 7b and FIG.
  • the optical characteristic curve of the straight lens The relevant parameters of each lens in the collimating lens of this embodiment are shown in Table 3-1.
  • the schematic diagram of the cross-sectional structure of the collimating lens provided in the fourth embodiment of the present invention is substantially the same as that of the first embodiment, and will not be further described herein. Referring to FIG. 9a, FIG. 9b and FIG. 10, respectively, the reference in this embodiment is shown. For the optical characteristic curve of the straight lens, the relevant parameters of each lens in the collimating lens of this embodiment are shown in Table 4-1.
  • the second lens L2 is an aspherical lens having both surfaces concave.
  • FIG. 12a, FIG. 12b and FIG. 13 respectively show the optical characteristic curves of the collimating lens in this embodiment.
  • the relevant parameters of each lens in the collimating lens of this embodiment are shown in Table 5-1.
  • Table 6 is the above five embodiments and their corresponding optical characteristics, including the system focal length f, the numerical aperture NA, and the system optical total length TTL, and values corresponding to each of the preceding conditional expressions.

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Abstract

本发明公开了一种准直镜头，从激光发射器端到被测物体端依次包括：第一透镜，第二透镜，第三透镜和光阑，光阑为最靠近像侧的位置。第一透镜为具有正光焦度的透镜，且靠近物侧表面为凸面；第二透镜为具有负光焦度的透镜，且靠近物侧表面为凹面；第三透镜为具有正光焦度的透镜，且靠近像侧表面为凸面；且各个透镜的光学中心位于同一直线上。该准直镜头由于各镜片的折射率随温度的变化率分配合理，能实现焦距稳定及适用于不同的温度场合。靠近激光发射器的第一透镜的折射率在0～60℃范围内随温度的变化率满足(dn/dt)1>-10×10 -6/℃，可以有效延缓镜头的老化；且在同样尺寸的激光发射器下，系统的焦距更大，视场角更小，更有利于3D结构光的算法实现。

Description

准直镜头
相关申请的交叉引用
本申请要求江西联益光学有限公司于2018年3月9日提交的、发明名称为“准直镜头”的、中国专利申请号“201810195341.7”的优先权。
技术领域
本发明涉及摄像镜头技术领域，特别是涉及一种准直镜头。
背景技术
随着智能手机的快速发展，手机的摄像功能也不断涌现出创新的技术，比如苹果公司主推的3D成像技术，这种基于3D结构光的光学感测技术，可用于人脸、手势辨识，强化照相功能，带来AR新应用，将光学图像从过去的二维向三维空间转换，从而带来更加真实、清晰的感知体验。
3D结构光是指将特定的激光信息投射到物体表面后，由摄像头采集，根据物体造成的光信息的变化来计算物体的位置和深度等信息，进而复原整个三维空间。特定的激光信息是3D结构光技术中的一个非常重要的指标，因此对把激光信息投影到被测物体表面的准直镜头要求很高。这种把VCSEL(垂直腔面发射激光器)激光器表面的有特定立体角发射的阵列点光源投影到被测物体表面的准直镜头，是3D成像质量的一个关键环节。
在现有的这类产品中，存在随着使用环境下温度的变化，镜头焦距f发生较大变化，从而导致镜头投射光的角度发生明显变化，这会改变原有的光信息，从而导致整个系统的计算出现误差，影响三维物体的轮廓复原精度；同样还存在随着温度的变化，投影的像点变大的情况，这也会导致系统还原三维物体的清晰度下降。因此在随着使用环境温度变化的情况下，投射到被测物体的光信息的视场角和斑点的大小不发生较大的变化就显得尤为重要。
此外，一般传统的准直镜头靠近激光发射器的第一透镜为塑胶镜片，这种镜片容易老化；而且这种镜头的信赖性试验难以通过。
发明内容
本发明旨在至少解决现有技术中存在的技术问题之一。为此，本发明的目的在于提出一种在不同温度下焦距稳定、且信赖性更强的准直镜头。
根据本发明提供的准直镜头，从激光发射器端到被测物体端依次包括：
具有正光焦度的第一透镜，其物侧表面为凸面；
具有负光焦度的第二透镜，其物侧表面为凹面；
具有正光焦度的第三透镜；其像侧表面为凸面；
靠近所述被测物体端的光；
各个透镜的光学中心位于同一直线上；
所述准直镜头满足以下条件式：
f1<f23；
(dn/dt)1>-10×10 -6/℃；
(dn/dt)2<-50×10 -6/℃；
(dn/dt)3<-50×10 -6/℃；
其中，所述激光发射器端为物侧，所述被测物体端为像侧，f1表示所述第一透镜的焦距，f23表示所述第二透镜和所述第三透镜的组合焦距，(dn/dt)1、(dn/dt)2和(dn/dt)3分别表示所述第一透镜、所述第二透镜和所述第三透镜的折射率在0～60℃范围内随温度的变化率。所述准直镜头，由于各镜片的折射率随温度的变化率分配合理，能够和镜片本身及结构件带来的热膨胀对焦距的影响相抵消，所以能够实现焦距稳定及适用于不同的温度场合。能够达到温度每变化10℃，该准直镜头的有效焦距变化量小于0.001mm，以致镜头投射光的角度不发生明显变化，不改变原有的光信息。且该准直镜头，靠近激光发射器的第一透镜的折射率在0～60℃范围内随温度的变化率满足(dn/dt)1>-10×10 -6/℃，具有该材质特性的第一透镜可以有效延缓镜头的老化，信赖性更强，更容易通过信赖性试验，且试验结果稳定。
进一步地，所述准直镜头满足条件式：
TTL/f＜1.0；
其中，TTL表示所述准直镜头的光学总长，f表示所述准直镜头的系统焦距。
进一步地，所述准直镜头满足条件式：
0＜f3/f1＜5；
其中，f3表示所述第三透镜的焦距，f1表示所述第一透镜的焦距。
进一步地，所述准直镜头满足条件式：
0＜f/r1＜10；
其中，f表示所述准直镜头的系统焦距，r1表示所述第一透镜物侧表面的曲率半径：
进一步地，所述准直镜头满足条件式：
-10＜r1/r6＜0；
其中，r1表示所述第一透镜物侧表面的曲率半径，r6表示所述第三透镜像侧表面的曲率半径。
进一步地，所述准直镜头满足条件式：
0＜CT3/CT1＜5；
其中，CT1表示所述第一透镜的中心厚度，CT3表示所述第三透镜的中心厚度。
进一步地，所述第一透镜、所述第二透镜和所述第三透镜的各物侧表面与像侧表面均为非球面。
进一步地，所述第一透镜为玻璃材质，所述第二透镜和所述第三透镜为塑胶材质。
进一步地，所述准直镜头中各透镜的非球面表面形状均满足下列方程：
Figure PCTCN2018081611-appb-000001
其中，z表示曲面离开曲面顶点在光轴方向的距离，c表示曲面顶点的曲率，k表示二次曲面系数，h表示光轴到曲面的距离，B、C、D、E、F、G、H分别表示四阶、六阶、八阶、十阶、十二阶、十四阶、十六阶曲面系数。
本发明的优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本发明的实践了解到。
附图说明
本发明的上述和/或附加的方面和优点从结合下面附图对实施例的描述中将变得明显和容易理解，其中：
图1是根据本发明一实施方式的准直镜头的截面结构示意图；
图2是激光发射器的发射光经过图1中的准直镜头的光学线路示意图；
图3a是本发明实施例1中的准直镜头在40℃，300mm像距成像时的场曲曲线图，图中x轴为场曲值，坐标单位为毫米，y轴为用物高定义的视场；
图3b是本发明实施例1中的准直镜头在40℃，300mm像距成像时的畸变曲线图，图中x轴为畸变值，坐标单位为百分比，y轴为用物高定义的视场；
图4为本发明实施例1中的准直镜头在40℃，300mm像距成像时像点大小及形状的示意图，单位为微米；
图5a是本发明实施例2中的准直镜头在40℃，300mm像距成像时的场曲曲线图；
图5b是本发明实施例2中的准直镜头在40℃，300mm像距成像时的畸变曲线图；
图6为本发明实施例2中的准直镜头在40℃，300mm像距成像时像点大小及形状的示意图，单位为微米；
图7a是本发明实施例3中的准直镜头在40℃，300mm像距成像时的场曲曲线图；
图7b是本发明实施例3中的准直镜头在40℃，300mm像距成像时的畸变曲线图；
图8为本发明实施例3中的准直镜头在40℃，300mm像距成像时像点大小及形状的示意图，单位为微米；
图9a是本发明实施例4中的准直镜头在40℃，300mm像距成像时的场曲曲线图；
图9b是本发明实施例4中的准直镜头在40℃，300mm像距成像时的畸变曲线图；
图10为本发明实施例4中的准直镜头在40℃，300mm像距成像时像点大小及形状的示意图，单位为微米；
图11是本发明实施例5的准直镜头的截面结构示意图；
图12a是本发明实施例5中的准直镜头在40℃，300mm像距成像时的场曲曲线图；
图12b是本发明实施例5中的准直镜头在40℃，300mm像距成像时的畸变曲线图；
图13为本发明实施例5中的准直镜头在40℃，300mm像距成像时像点大小及形状的示意图，单位为微米。
具体实施方式
为使本发明的目的、特征和优点能够更加明显易懂，下面结合附图对本发明的具体实施方式做详细的说明。附图中给出了本发明的若干实施例。但是，本发明可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本发明的公开内容更加透彻全面。
除非另有定义，本文所使用的所有的技术和科学术语与属于本发明的技术领域的技术人员通常理解的含义相同。本文中在本发明的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本发明。本文所使用的术语“及/或”包括一个或多个相关的所列项目的任意的和所有的组合。
请参阅图1，本发明的一实施方式提供的准直镜头10，包括靠近激光发射器20(也即物侧)且具有正光焦度的第一透镜L1，具有负光焦度的第二透镜L2，具有正光焦度的第三透镜L3，靠近被测物体(也即像侧)的光阑S7；且各个透镜的光学中心位于同一直线上。
所述第一透镜L1具有正光焦度，其物侧表面为凸面，借此汇聚来自激光器的远心光束，且搭配第一透镜L1提供足够的正光焦度，可有效地控制光学透镜组的整体体积。
所述第二透镜L2具有负光焦度，其物侧表面为凹面，可有效地调和第一透镜L1所产生的像差，亦能控制工作波段的聚焦能力。
所述第三透镜L3具有正光焦度，其像侧表面为凸面，可以有效修正光学透镜的像差，可有效地控制出射角度。
所述第一透镜L1、第二透镜L2及第三透镜L3的物侧表面及像侧表面皆为非球面，也即第一透镜L1、第二透镜L2及第三透镜L3的物侧表面及像侧表面是制作成球面以外的形状，借此可以获得较多的控制变数，以削减像差。
本实施方式提供的准直镜头10满足以下条件式：
f1<f23；
(dn/dt)1>-10×10 -6/℃；
(dn/dt)2<-50×10 -6/℃；
(dn/dt)3<-50×10 -6/℃；
其中，f1表示第一透镜的焦距，f23表示第二透镜和第三透镜的组合焦距，(dn/dt)1、(dn/dt)2和(dn/dt)3分别表示第一透镜、第二透镜和第三透镜的折射率在0～60℃范围内随温度的变化率。
上述准直镜头，由于各镜片的折射率随温度的变化率分配合理，能够和镜片本身及结构件带来的热膨胀对焦距的影响相抵消，所以能够实现焦距稳定及适用于不同的温度场合；能够达到温度每变化10℃，该准直镜头的有效焦距变化量小于0.001mm，以致镜头投射光的角度不发生明显变化，不改变原有的光信息。且相比现有技术，在同样尺寸的VCSEL(激光发射器)下，可以实现系统的焦距更大，视场角更小，从而更有利于3D结构光的算法实现。
请参阅图2，所述为激光发射器20的发射光线30经过所述准直镜头10的光学线路示意图，本发明提供的准直镜头10中，靠近激光发射器端20的第一透镜L1的折射率在0～60℃范围内随温度的变化率满足(dn/dt)1>-10×10 -6/℃，具有该材质特性的第一透镜，也即为玻璃材质的透镜，由于激光发射器是发光源，靠近发光源的第一透镜采用玻璃材质，可以有效延缓镜头的老化，信赖性更强，更容易通过信赖性试验，且试验结果稳定。同时，远离发光源的第二透镜L2和第三透镜L3可为塑胶材质，借以有效降低生产成本。
上述准直镜头10中，所述第一透镜L1的焦距f1与所述第二透镜L2、第三透镜L3的组合焦距f23的差值均小于0，满足条件f1<f23，此条件限制了第二透镜L2、第三透镜L3组合与第一透镜L1相比对光线的偏折能力更弱。
进一步地，所述第一透镜L1、第二透镜L2及第三透镜L3的折射率在0～60℃范围内随温度的变化率(dn/dt)1、(dn/dt)2及(dn/dt)3满足条件(dn/dt)1>-10×10 -6/℃，(dn/dt)2<-50×10 -6/℃，(dn/dt)3<-50×10 -6/℃。此条件限制了三个透镜的折射率随温度的变化率，主要用于合理的搭配镜片的热膨胀，保证在不同温度下镜头焦距的稳定性。
进一步地，所述准直镜头10的光学总长TTL与系统焦距f满足条件式：TTL/f＜1.0，此条件限制了系统总长和系统焦距的比例关系，在保证系统长焦距的情况下，能达到系统 小型化的目的。具体的，可以限定，所述准直镜头10的光学总长TTL小于3.5mm，且所述准直镜头10的系统焦距f大于3.5mm，以保证更好的光学特性，更适合3D结构光的算法实现。
进一步地，所述第三透镜L3的焦距f3所述第一透镜L1的焦距f1的比值范围为：0＜f3/f1＜5。此条件限制了所述第一透镜L1与第三透镜L3的配比，主要用于将经过所述第三透镜L3的光线会聚于成像面上，同时减少所述准直镜头的像差。
进一步地，所述准直镜头10的系统焦距f与第一透镜L1物侧表面的曲率半径r1的比值范围为：0＜f/r1＜10，此条件限制了第一透镜L1物侧面的形状，有利于镜片的加工制造，同时可以降低公差敏感度。
进一步地，所述第一透镜L1物侧表面的曲率半径r1与所述第三透镜L3像侧表面的曲率半径r6比值范围为：-10＜r1/r6<0。此条件限制了所述第一透镜L1物侧表面与第三透镜侧L3像侧表面的朝向相反，主要用于将经过所述第三透镜L3的光线会聚于成像面上，同时减少所述准直镜头的像差。
进一步地，所述第三透镜L3的中心厚度CT3与第一透镜L1的中心厚度CT1的比值范围为：0＜CT3/CT1＜5，此条件限制了所述第三透镜L3的中心厚度与第一透镜L1的中心厚度的配比，借由适当配置透镜的中心厚度，有利于光学透镜组的加工制造及组装。
进一步地，所述第一透镜L1、所述第二透镜L2和所述第三透镜L3的各物侧表面与像侧表面均为非球面，借此可以获得较多的控制变数，以削减像差。
综上，该准直镜头10的尺寸更小，能够实现焦距稳定及适用于不同的温度场合。各镜片的折射率随温度的变化率及热膨胀系数分配合理，以致镜头投射光的角度不生明显变化，不改变原有的光信息；且在搭配同样尺寸的VCSEL(激光发射器)下，可以实现系统的焦距更大，视场角更小，从而更有利于3D结构光的算法实现。靠近激光发射器的第一透镜L1材料为玻璃，可以有效延缓镜头的老化；并且通过信赖性试验，且试验结果稳定。
下面分多个实施例对本发明进行进一步的说明。在以下每个实施例中，准直镜头中的各个透镜的厚度、曲率半径有所不同，具体不同可参见各实施例中的参数表。下述实施例仅为本发明的较佳实施方式，但本发明的实施方式并不仅仅受下述实施例的限制，其他的任何未背离本发明创新点所作的改变、替代、组合或简化，都应视为等效的置换方式，都包含在本发明的保护范围之内。
在本发明的所有实施例中，r表示光学曲面顶点的曲率半径，d表示光学表面间距(相邻的两个光学曲面顶点之间的距离)，nd表示各个透镜的折射率，Vd表示各个透镜的阿贝数，用来衡量介质的光线色散程度。
本发明各个实施例中所述准直镜头的非球面表面形状均满足下列方程：
Figure PCTCN2018081611-appb-000002
其中，z表示曲面离开曲面顶点在光轴方向的距离，c表示曲面顶点的曲率，k表示二次曲面系数，h表示光轴到曲面的距离，B、C、D、E、F、G、H分别表示四阶、六阶、八阶、十阶、十二阶、十四阶、十六阶曲面系数。
在以下各个实施例中，所述准直镜头中的各个透镜的厚度、曲率半径部分有所不同，具体不同可参见各实施例的参数表。
实施例1：
本实施例的准直镜头的截面结构示意图可参阅图1，在本实施例中，第二透镜L2是物侧表面为凹面、像侧表面为凸面的非球面镜片。同时请参阅图3a、3b及图4，其分别示出了本实施例中准直镜头的光学特性曲线。本实施例中的准直镜头中各个镜片的相关参数如表1-1所示。
表1-1
Figure PCTCN2018081611-appb-000003
本实施例的各透镜非球面的参数如表1-2所示。
表1-2
Figure PCTCN2018081611-appb-000004
Figure PCTCN2018081611-appb-000005
实施例2
本发明第二实施例中提供的准直镜头的截面结构示意图与第一实施例大抵相同，在此不予赘述，请参阅图5a、5b及图6，其分别示出了本实施例中准直镜头的光学特性曲线。本实施例的准直镜头中各个镜片的相关参数如表2-1所示。
表2-1
Figure PCTCN2018081611-appb-000006
本实施例的各透镜非球面的参数如表2-2所示。
表2-2
Figure PCTCN2018081611-appb-000007
实施例3
本发明第三实施例中提供的准直镜头的截面结构示意图与第一实施例大抵相同，在此不予赘述，请参阅图7a、7b及图8，其分别示出了本实施例中准直镜头的光学特性曲线。本实施例的准直镜头中各个镜片的相关参数如表3-1所示。
表3-1
Figure PCTCN2018081611-appb-000008
本实施例的各透镜非球面的参数如表3-2所示。
表3-2
Figure PCTCN2018081611-appb-000009
实施例4
本发明第四实施例中提供的准直镜头的截面结构示意图与第一实施例大抵相同，在此不予赘述，请参阅图9a、9b及图10，其分别示出了本实施例中准直镜头的光学特性曲线，本实施例的准直镜头中各个镜片的相关参数如表4-1所示。
表4-1
Figure PCTCN2018081611-appb-000010
本实施例的各透镜非球面的参数如表4-2所示。
表4-2
Figure PCTCN2018081611-appb-000011
实施例5
请参阅图11，本发明第五实施例中提供的准直镜头的截面结构示意图，在本实施例中，第二透镜L2为双面皆为凹面的非球面透镜。
请参阅图12a、12b及图13，其分别示出了本实施例中准直镜头的光学特性曲线，本实施例的准直镜头中各个镜片的相关参数如表5-1所示。
表5-1
Figure PCTCN2018081611-appb-000012
Figure PCTCN2018081611-appb-000013
本实施例的各透镜非球面的参数如表5-2所示。
表5-2
Figure PCTCN2018081611-appb-000014
由于像点的数据范围越小，说明镜头性能越好，从各个实施例中的图4、图6、图8、图10和图13可以得出，每个实施例中的像差被很好的校正。
表6是上述5个实施例及其对应的光学特性，包括系统焦距f、数值孔径NA和系统光学总长TTL，以及与前面每个条件式对应的数值。
表6
Figure PCTCN2018081611-appb-000015
Figure PCTCN2018081611-appb-000016
在本说明书的描述中，参考术语“一个实施例”、“一些实施例”、“示例”、“具体示例”、或“一些示例”等的描述意指结合该实施例或示例描述的具体特征、结构、材料或者特点包含于本发明的至少一个实施例或示例中。在本说明书中，对上述术语的示意性表述不一定指的是相同的实施例或示例。而且，描述的具体特征、结构、材料或者特点可以在任何的一个或多个实施例或示例中以合适的方式结合。
以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (9)

  1. 一种准直镜头，其特征在于，从激光发射器端到被测物体端依次包括：
    具有正光焦度的第一透镜，其物侧表面为凸面；
    具有负光焦度的第二透镜，其物侧表面为凹面；
    具有正光焦度的第三透镜，其像侧表面为凸面；
    靠近所述被测物体端的光阑；
    各个透镜的光学中心位于同一直线上；
    所述准直镜头满足以下条件式：
    f1<f23；
    (dn/dt)1>-10×10 -6/℃；
    (dn/dt)2<-50×10 -6/℃；
    (dn/dt)3<-50×10 -6/℃；
    其中，所述激光发射器端为物侧，所述被测物体端为像侧，f1表示所述第一透镜的焦距，f23表示所述第二透镜和所述第三透镜的组合焦距，(dn/dt)1、(dn/dt)2和(dn/dt)3分别表示所述第一透镜、所述第二透镜和所述第三透镜的折射率在0～60℃范围内随温度的变化率。
  2. 根据权利要求1所述的准直镜头，其特征在于，所述准直镜头满足条件式：
    TTL/f＜1.0；
    其中，TTL表示所述准直镜头的光学总长，f表示所述准直镜头的系统焦距。
  3. 根据权利要求1所述的准直镜头，其特征在于，所述准直镜头满足条件式：
    0＜f3/f1＜5；
    其中，f3表示所述第三透镜的焦距，f1表示所述第一透镜的焦距。
  4. 根据权利要求1所述的准直镜头，其特征在于，所述准直镜头满足条件式：
    0＜f/r1＜10；
    其中，f表示所述准直镜头的系统焦距，r1表示所述第一透镜物侧表面的曲率半径：
  5. 根据权利要求1所述的准直镜头，其特征在于，所述准直镜头满足条件式：
    -10＜r1/r6＜0；
    其中，r1表示所述第一透镜物侧表面的曲率半径，r6表示所述第三透镜像侧表面的曲率半径。
  6. 根据权利要求1所述的准直镜头，其特征在于，所述准直镜头满足条件式：
    0＜CT3/CT1＜5；
    其中，CT1表示所述第一透镜的中心厚度，CT3表示所述第三透镜的中心厚度。
  7. 根据权利要求1所述的准直镜头，其特征在于，所述第一透镜、所述第二透镜和所述第三透镜的各物侧表面与像侧表面均为非球面。
  8. 根据权利要求1所述的准直镜头，其特征在于，所述第一透镜为玻璃材质，所述第二透镜和所述第三透镜为塑胶材质。
  9. 根据权利要求7所述的准直镜头，其特征在于，所述准直镜头中各透镜的非球面表面形状均满足下列方程：
    Figure PCTCN2018081611-appb-100001
    其中，z表示曲面离开曲面顶点在光轴方向的距离，c表示曲面顶点的曲率，k表示二次曲面系数，h表示光轴到曲面的距离，B、C、D、E、F、G、H分别表示四阶、六阶、八阶、十阶、十二阶、十四阶、十六阶曲面系数。
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