WO2019148639A1 - 准直镜头 - Google Patents

准直镜头 Download PDF

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Publication number
WO2019148639A1
WO2019148639A1 PCT/CN2018/081612 CN2018081612W WO2019148639A1 WO 2019148639 A1 WO2019148639 A1 WO 2019148639A1 CN 2018081612 W CN2018081612 W CN 2018081612W WO 2019148639 A1 WO2019148639 A1 WO 2019148639A1
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Prior art keywords
lens
collimating lens
collimating
focal length
order
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PCT/CN2018/081612
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English (en)
French (fr)
Inventor
刘绪明
曾昊杰
鲍宇旻
陈伟建
曾吉勇
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江西联益光学有限公司
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Application filed by 江西联益光学有限公司 filed Critical 江西联益光学有限公司
Priority to US16/326,378 priority Critical patent/US10989930B2/en
Publication of WO2019148639A1 publication Critical patent/WO2019148639A1/zh

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    • 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
    • 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
    • G02B13/004—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 four lenses
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B13/00—Optical objectives specially designed for the purposes specified below
    • G02B13/16—Optical objectives specially designed for the purposes specified below for use in conjunction with image converters or intensifiers, or for use with projectors, e.g. objectives for projection TV
    • 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
    • G02B27/18—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical projection, e.g. combination of mirror and condenser and objective
    • G02B27/20—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 for optical projection, e.g. combination of mirror and condenser and objective for imaging minute objects, e.g. light-pointer
    • 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
    • G02B7/00—Mountings, adjusting means, or light-tight connections, for optical elements
    • G02B7/02—Mountings, adjusting means, or light-tight connections, for optical elements for lenses
    • G02B7/028—Mountings, adjusting means, or light-tight connections, for optical elements for lenses with means for compensating for changes in temperature or for controlling the temperature; thermal stabilisation

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 present invention aims to solve at least one of the technical problems existing in the prior art.
  • the object of the present invention is to provide a collimating lens with a stable focal length at different temperatures.
  • the laser emitter end to the object end to be tested includes:
  • the object side surface and the image side surface are both concave surfaces
  • optical centers of the respective lenses are on the same straight line
  • the collimating lens satisfies the following conditional formula:
  • (dn/dt)1, (dn/dt)2, (dn/dt)3, (dn/dt)4 represent the first lens, the second lens, the third lens, and the The refractive index of the fourth lens varies with temperature in the range of 0 to 60 °C.
  • the collimating lens since the refractive index of each lens is properly distributed with temperature, the effect 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 adapted to different
  • the temperature occasion can reach the temperature change of 10 degrees Celsius, the effective focal length variation of the collimating lens is less than 0.0005 mm, so that the angle of the projected light of the lens does not change significantly, and the original optical information is not changed.
  • 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.
  • the collimating lens satisfies the following conditional expression:
  • TTL represents the total optical length of the collimating lens
  • f represents the focal length of the system of the collimating lens
  • both sides of the first lens, the second lens, the third lens and the fourth lens are aspherical surfaces.
  • the collimating lens satisfies the conditional expression:
  • f4 represents the focal length of the fourth lens
  • f1 represents the focal length of the first lens
  • the collimating lens satisfies the conditional expression:
  • f represents the focal length of the system of the collimating lens
  • R8 represents the radius of curvature of the side surface of the fourth lens image.
  • the collimating lens satisfies the conditional expression:
  • R1 represents the radius of curvature of the first lens object side surface
  • R8 represents the radius of curvature of the fourth lens image side surface
  • the collimating lens satisfies the conditional expression:
  • CT2 represents the center thickness of the second lens
  • CT4 represents the center thickness of the fourth lens
  • the optical total length TTL of the collimating lens is less than 3.5 mm.
  • system focal length f of the collimating lens is greater than 4.45 mm.
  • 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;
  • 3a is a field curvature curve of a collimating lens according to Embodiment 1 of the present invention at 40° C. and 400 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 a collimating lens according to Embodiment 1 of the present invention at 40° C. and 400 mm image distance, in which the x-axis is a distortion value, the coordinate unit is a percentage, and the y-axis is a definition defined by the object height. field;
  • 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 400 mm image distance, in units of micrometers;
  • Figure 5 is a cross-sectional structural view of a collimating lens according to Embodiment 2 of the present invention.
  • 6a is a field curvature diagram of a collimating lens according to Embodiment 2 of the present invention at 40° C. and 400 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.
  • 6b is a distortion diagram of a collimating lens according to Embodiment 2 of the present invention at 40° C. and 400 mm image distance, in which the x-axis is a distortion value, the coordinate unit is a percentage, and the y-axis is a definition defined by the object height. field;
  • FIG. 7 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 400 mm image distance, in units of micrometers;
  • Figure 8 is a cross-sectional structural view of a collimating lens according to Embodiment 3 of the present invention.
  • 9a is a field curvature curve of a collimating lens according to Embodiment 3 of the present invention at 40° C. and 400 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.
  • 9b is a distortion diagram of a collimating lens according to Embodiment 3 of the present invention at 40° C. and 400 mm image distance, in which the x-axis is a distortion value, the coordinate unit is a percentage, and the y-axis is a definition defined by the object height. field;
  • Figure 10 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, 400 mm image distance, in micrometers;
  • Figure 11 is a cross-sectional structural view of a collimating lens according to Embodiment 4 of the present invention.
  • Figure 12a is a plot of field curvature of a collimating lens according to Embodiment 4 of the present invention at 40 ° C, 400 mm image distance, in which the x-axis is the field curvature value, the coordinate unit is mm, and the y-axis is defined by the object height.
  • 12b is a distortion diagram of a collimating lens according to Embodiment 4 of the present invention at 40° C. and 400 mm image distance, in which the x-axis is a distortion value, the coordinate unit is a percentage, and the y-axis is a definition defined by the object height. field;
  • Fig. 13 is a view showing the size and shape of a pixel of a collimating lens according to Embodiment 4 of the present invention at 40 ° C, 400 mm image distance, in micrometers.
  • a collimating lens 10 includes a first lens L1 having a positive power close to the laser emitter 20 (ie, the object side), having a negative power. a second lens L2, a third lens L3 having positive refractive power, a fourth lens L4 having positive refractive power, close to the pupil S9 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 a positive power, the object side surface is a convex surface, and the object side surface and the image side surface are all aspherical surfaces, thereby concentrating the telecentric light beam from the laser emitter 20, and the first lens L1 provides sufficient
  • the positive power can effectively control the overall volume of the optical lens unit.
  • the second lens L2 has a negative refractive power, and both the object side surface and the image side surface are concave aspheric surfaces, which can effectively adjust the aberration generated by the first lens L1 and also control the focusing ability of the working band.
  • the third lens L3 has positive refractive power, and both the object side surface and the image side surface are aspherical.
  • the fourth lens L4 has positive refractive power, and the image side surface is convex, and the object side surface and the image side surface are all aspherical surfaces, which can effectively correct the aberration of the optical lens, thereby effectively controlling the exit angle of the light.
  • the collimating lens 10 provided by the present embodiment satisfies the following conditional expression:
  • (dn/dt)1, (dn/dt)2, (dn/dt)3, and (dn/dt)4 represent the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4, respectively
  • the refractive index varies with temperature in the range of 0 to 60 °C.
  • the refractive index of each lens is distributed reasonably with temperature, so that the focal length can be stabilized and applied to different temperature occasions; It can reach the temperature change of 10 degrees Celsius, the effective focal length change of the collimating lens is less than 0.0005mm, so that the angle of the projected light of the lens does not change significantly, and the original optical information is not changed.
  • 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.
  • the first lens L1, the second lens L2, and the third lens L3 are made of a plastic material, so as to effectively reduce the production cost, the fourth lens L4 can be made of glass to ensure the change with the working temperature.
  • the system resolution does not change significantly.
  • 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 system focal length f of the collimating lens 10 is greater than 4.45 mm to ensure better optical characteristics, and is more suitable for 3D structured light algorithms. achieve.
  • the object side surface and the image side surface of the first lens L1, the second lens L2, the third lens L3, and the fourth lens L4 are all aspherical surfaces, that is, the first lens L1, the second lens L2, and the third lens L3. Further, the object side surface and the image side surface of the fourth lens L4 are formed into a shape other than a spherical surface, whereby a large number of control variables can be obtained to reduce aberrations.
  • the first lens L1 to the fourth lens L4 are four non-adhesive independent lenses: in other words, in the optical lens group of the present invention, the first lens L1 and the second lens L2 Among the three lenses L3 and the fourth lens L4, there are air gaps between any two adjacent lenses having power. Since the process of bonding the lenses is more complicated than that of the non-adhesive lenses, especially the bonding faces of the two lenses must have a high The precise surface is used to achieve high adhesion when the two lenses are bonded, and in the bonding process, the adhesion may be poor due to the offset, and the image optical imaging quality. Therefore, in the optical lens unit of the present invention, the first lens L1 to the fourth lens L4 are four non-adhesive independent lenses, which can effectively improve the problems caused by the adhesive lens.
  • the ratio of the focal length f4 of the fourth lens L4 to the focal length f1 of the first lens L1 is:
  • the ratio of the system focal length f of the collimating lens 10 to the radius of curvature R8 of the image side surface of the fourth lens L4 is:
  • this condition limits the shape of the side surface of the fourth lens L4, which is advantageous for the manufacturing of the lens while reducing the tolerance sensitivity.
  • the ratio of the radius of curvature R1 of the object side surface of the first lens L1 to the radius of curvature R8 of the image side surface of the fourth lens L4 is:
  • this condition restricts the opposite direction of the object side surface of the first lens L1 from the image side surface of the fourth lens L4, and is mainly used for concentrating the light passing through the first lens L1 on the imaging surface while The aberration of the collimating lens 10 is reduced.
  • the ratio of the center thickness CT4 of the fourth lens L4 to the center thickness CT2 of the second lens L2 is:
  • the collimating lens 10 is smaller in size, can achieve stable focal length and is suitable for different temperature occasions.
  • 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),
  • VCSEL laser emitter
  • 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.
  • 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 For a structural diagram of the collimating lens of this embodiment, refer to FIG. 1 , and please refer to FIG. 3 a , 3 b and FIG. 4 , and related parameters of each lens in the collimating lens are shown in Table 1-1.
  • FIG. 5 Please refer to FIG. 5, FIG. 6a, FIG. 6b and FIG. 7 , which are collimating lenses provided in the second embodiment of the present invention.
  • the relevant parameters of each lens in the collimating lens are shown in Table 2-1.
  • FIG. 8 Please refer to FIG. 8, FIG. 9a, FIG. 9b and FIG. 10, which are collimating lenses provided in the third embodiment of the present invention.
  • the relevant parameters of each lens in the collimating lens are shown in Table 3-1.
  • FIG. 11 Please refer to FIG. 11, FIG. 12a, FIG. 12b and FIG. 13 for the collimating lens provided in the fourth embodiment of the present invention.
  • the relevant parameters of each lens in the collimating lens are shown in Table 4-1.
  • Table 5 is the above four 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：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，其物侧表面和像侧表面均为凹面；具有正光焦度的第三透镜；具有正光焦度的第四透镜，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；该准直镜头满足以下条件式：(dn/dt)1<-50×10 -6/℃；(dn/dt)2<-50×10 -6/℃；(dn/dt)3<-50×10 -6/℃；(dn/dt)4>-10×10 -6/℃；其中，(dn/dt)1、(dn/dt)2、(dn/dt)3、(dn/dt)4分别表示第一透镜、第二透镜、第三透镜和第四透镜的折射率在0～60℃范围内随温度的变化率。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。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1月30日提交的、发明名称为“准直镜头”的、中国专利申请号“201810086735.9”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，准直的像点变大的情况，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。
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，其物侧表面和像侧表面均为凹面；
具有正光焦度的第三透镜；
具有正光焦度的第四透镜，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：
(dn/dt)1<-50×10 -6/℃；
(dn/dt)2<-50×10 -6/℃；
(dn/dt)3<-50×10 -6/℃；
(dn/dt)4>-10×10 -6/℃；
其中，(dn/dt)1、(dn/dt)2、(dn/dt)3、(dn/dt)4分别表示所述第一透镜、所述第二透镜、所述第三透镜和所述第四透镜的折射率在0～60℃范围内随温度的变化率。
根据本发明提供的准直镜头，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摄氏度，该准直镜头的有效焦距变化量小于0.0005mm，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。
进一步地，所述准直镜头满足以下条件式：
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，所述第一透镜、所述第二透镜、所述第三透镜和所述第四透镜的两侧均为非球面。
进一步地，所述准直镜头满足条件式：
0＜f4/f1＜5.0；
其中，f4表示所述第四透镜的焦距，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：
-6.0＜f/R8＜0；
其中，f表示所述准直镜头的系统焦距，R8表示所述第四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：
-5.0＜R1/R8＜0；
其中，R1表示所述第一透镜物侧表面的曲率半径，R8表示所述第四透镜像侧表面的 曲率半径。
进一步地，所述准直镜头满足条件式：
1.0＜CT4/CT2＜5.0；
其中，CT2表示所述第二透镜的中心厚度，CT4表示所述第四透镜的中心厚度。
进一步地，所述准直镜头的光学总长TTL小于3.5mm。
进一步地，所述准直镜头的系统焦距f大于4.45mm。
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 PCTCN2018081612-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是根据本发明实施例1中的准直镜头在40℃，400mm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是根据本发明实施例1中的准直镜头在40℃，400mm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是根据本发明实施例1中的准直镜头在40℃，400mm像距成像时像点大小及形状的示意图，单位为微米；
图5是根据本发明实施例2中的准直镜头的截面结构示意图；
图6a是根据本发明实施例2中的准直镜头在40℃，400mm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6b是根据本发明实施例2中的准直镜头在40℃，400mm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7是根据本发明实施例2中的准直镜头在40℃，400mm像距成像时像点大小及形状 的示意图，单位为微米；
图8是根据本发明实施例3中的准直镜头的截面结构示意图；
图9a是根据本发明实施例3中的准直镜头在40℃，400mm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9b是根据本发明实施例3中的准直镜头在40℃，400mm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10是根据本发明实施例3中的准直镜头在40℃，400mm像距成像时像点大小及形状的示意图，单位为微米；
图11是根据本发明实施例4中的准直镜头的截面结构示意图；
图12a是根据本发明实施例4中的准直镜头在40℃，400mm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12b是根据本发明实施例4中的准直镜头在40℃，400mm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13是根据本发明实施例4中的准直镜头在40℃，400mm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及图2，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，具有正光焦度的第四透镜L4，靠近被测物体(也即像侧)的光阑S9；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，且物侧表面及像侧表面皆为非球面，借此汇聚来自激光发射器20的远心光束，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，其物侧表面及像侧表面皆为凹面非球面，可有效的调和第一透镜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，其物侧表面及像侧表面皆为非球面。
所述第四透镜L4具有正光焦度，其像侧表面为凸面，其物侧表面及像侧表面皆为非球面，可以有效修正光学透镜的像差，从而有效地控制光线的出射角度。
本实施方式提供的准直镜头10满足以下条件式：
(dn/dt)1<-50×10 -6/℃；
(dn/dt)2<-50×10 -6/℃；
(dn/dt)3<-50×10 -6/℃；
(dn/dt)4>-10×10 -6/℃；
其中，(dn/dt)1、(dn/dt)2、(dn/dt)3和(dn/dt)4分别表示第一透镜L1、第二透镜L2、第三透镜L3和第四透镜L4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摄氏度，该准直镜头的有效焦距变化量小于0.0005mm，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。
上述准直镜头10中，限定所述第一透镜L1、第二透镜L2、第三透镜L3为塑胶材质，借以有效降低生产成本，第四透镜L4可为玻璃材质，以保证随工作温度的变化，系统解像力不发生明显变化。
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4.45mm，以保证更好的光学特性，更适合3D结构光的算法实现。
所述第一透镜L1、第二透镜L2、第三透镜L3及第四透镜L4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、第三透镜L3及第四透镜L4的物侧表面及像侧表面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。
在本发明的光学透镜组中，第一透镜L1至第四透镜L4为四片非粘合的独立透镜：换言之，在本发明的光学透镜组中，第一透镜L1、第二透镜L2、第三透镜L3及第四透镜L4中，任两相邻的具有光焦度的透镜间具有空气间隔，由于粘合透镜的工艺较非粘合透镜复 杂，特别在两透镜的粘合面须拥有高准度的曲面，以便达到两透镜粘合时的高密合度，且在粘合过程中，也可以因偏位而造成密合度不佳，影像光学成像品质。因此，本发明光学透镜组中，第一透镜L1至第四透镜L4为四片非粘合的独立透镜，可有效改善粘合透镜所产生的问题。
所述第四透镜L4的焦距f4与所述第一透镜L1的焦距f1的比值范围为：
0＜f4/f1＜5.0，此条件限制了第一透镜L1和第四透镜L4焦距的配比，主要用于将经过所述第一透镜L1的光线会聚于成像面上，同时减少所述准直镜头10的像差。
所述准直镜头10的系统焦距f与第四透镜L4像侧表面的曲率半径R8的比值范围为：
-6.0＜f/R8＜0，此条件限制了第四透镜L4像侧面的形状，有利于镜片的加工制造，同时可以降低公差敏感度。
所述第一透镜L1物侧表面的曲率半径R1与所述第四透镜L4像侧表面的曲率半径R8的比值范围为：
-5.0＜R1/R8＜0，此条件限制了第一透镜L1物侧表面与第四透镜L4像侧表面的朝向相反，主要用于将经过第一透镜L1的光线会聚于成像面上，同时减少所述准直镜头10的像差。
所述第四透镜L4的中心厚度CT4与所述第二透镜L2的中心厚度CT2的比值范围为：
1.0＜CT4/CT2＜5.0，此条件限制了第四透镜L4的中心厚度CT4与第二透镜L2的中心厚度CT2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。
综上，该准直镜头10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。
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。
本发明各个实施例中的各透镜的非球面表面形状均满足下列方程：
Figure PCTCN2018081612-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。
实施例1：
本实施例的准直镜头的结构图可参阅图1，同时请参阅图3a、3b及图4，所述准直镜头中各个镜片的相关参数如表1-1所示。
表1-1
Figure PCTCN2018081612-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 PCTCN2018081612-appb-000004
Figure PCTCN2018081612-appb-000005
实施例2
请参阅图5、图6a、6b及图7，为发明第二实施例中提供的准直镜头，所述准直镜头中各个镜片的相关参数如表2-1所示。
表2-1
Figure PCTCN2018081612-appb-000006
本实施例的各透镜非球面的参数如表2-2所示。
表2-3
Figure PCTCN2018081612-appb-000007
实施例3
请参阅图8、图9a、9b及图10，为发明第三实施例中提供的准直镜头，所述准直镜头中各个镜片的相关参数如表3-1所示。
表3-1
Figure PCTCN2018081612-appb-000008
本实施例的各透镜非球面的参数如表3-2所示。
表3-4
Figure PCTCN2018081612-appb-000009
实施例4
请参阅图11、图12a、12b及图13，为发明第四实施例中提供的准直镜头，所述准直镜头中各个镜片的相关参数如表4-1所示。
表4-1
Figure PCTCN2018081612-appb-000010
本实施例的各透镜非球面的参数如表4-2所示。
表4-5
Figure PCTCN2018081612-appb-000011
由于像点的数据范围越小，代表镜头性能越好，从各个实施例中的图4、图7、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5是上述4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5
Figure PCTCN2018081612-appb-000012
Figure PCTCN2018081612-appb-000013
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 (10)

  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，其物侧表面和像侧表面均为凹面；
    具有正光焦度的第三透镜；
    具有正光焦度的第四透镜，其像侧表面为凸面；
    靠近被测物体端的光阑；
    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：
    (dn/dt)1<-50×10 -6/℃；
    (dn/dt)2<-50×10 -6/℃；
    (dn/dt)3<-50×10 -6/℃；
    (dn/dt)4>-10×10 -6/℃；
    其中，(dn/dt)1、(dn/dt)2、(dn/dt)3和(dn/dt)4分别表示所述第一透镜、所述第二透镜、所述第三透镜和所述第四透镜的折射率在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，所述准直镜头满足以下条件式：
    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，所述第一透镜、所述第二透镜、所述第三透镜和所述第四透镜的两侧均为非球面。
  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＜f4/f1＜5.0；
    其中，f4表示所述第四透镜的焦距，f1表示所述第一透镜的焦距。
  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：
    -6.0＜f/R8＜0；
    其中，f表示所述准直镜头的系统焦距，R8表示所述第四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：
    -5.0＜R1/R8＜0；
    其中，R1表示所述第一透镜物侧表面的曲率半径，R8表示所述第四透镜像侧表面的曲率半径。
  7. 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：
    1.0＜CT4/CT2＜5.0；
    其中，CT2表示所述第二透镜的中心厚度，CT4表示所述第四透镜的中心厚度。
  8. 根据权利要求1至7任意一项所述的准直镜头，其特征在于，所述准直镜头的光学总长TTL小于3.5mm。
  9. 根据权利要求1至7任意一项所述的准直镜头，其特征在于，所述准直镜头的系统焦距f大于4.45mm。
  10. 根据权利要求1至7任意一项所述的准直镜头，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 PCTCN2018081612-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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CN112859342A (zh) * 2021-01-21 2021-05-28 谷东科技有限公司 用于增强现实的近眼显示装置和增强现实显示设备
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