A high-resolution time-of-flight measurement lens with large light throughput

Abstract

The present invention discloses a high-resolution time-of-flight measurement lens with large light flux, which includes a first lens to a sixth lens in sequence along an optical axis from the object side to the image side; the first lens to the sixth lens each include an object side surface facing the object side and allowing the imaging light to pass through, and an image side surface facing the image side and allowing the imaging light to pass through; the first lens has a negative refractive power; the second lens has a negative refractive power; the third lens has a positive refractive power; the fourth lens has a positive refractive power; the fifth lens has a positive refractive power; and the sixth lens has a negative refractive power. The optical imaging lens has only the above six lenses with refractive power. The present invention can improve signal utilization and increase the recognition range; control distortion and reduce the loss of effective pixels due to distortion; control relative illumination and ensure uniform relative illumination under large light flux conditions; the resolution reaches the high-resolution level in the TOF field and can meet the resolution requirements of the next generation of TOF sensors.

Description

Technical Field

[0001] The invention relates to the technical field of lenses, and in particular to a high-throughput and high-resolution time-of-flight measurement lens. Background Art

[0002] TOF (Time of flight) technology is an imaging technology that uses a group of infrared light (laser pulses) that are invisible to the human eye to be emitted outward, reflected after encountering an object, and reflected to the camera. The time difference or phase difference from emission to reflection back to the camera is calculated, and the data is collected to form a set of distance and depth data, thereby obtaining a three-dimensional 3D model. Therefore, TOF lenses are increasingly used in various fields such as VR / AR, autonomous driving, security monitoring, and automated production, but existing TOF lenses still have at least the following defects:

[0003] 1. The mainstream light transmission of TOF lenses on the market is far from the ideal light transmission value required for the application.

[0004] 2. The TOF lenses currently on the market have poor distortion control, and distortion correction results in a large number of pixel losses.

[0005] 3. The TOF on the current market sacrifices a lot of relative illumination of the edge field of view to achieve large clearance, and the illumination changes greatly.

[0006] 4. With the expansion of TOF application areas, some application scenarios have put forward the demand for miniaturization of lens size. At the same time, in order to ensure the current and near future recognition needs, the pixel size is further reduced as the target surface size is limited by the miniaturization demand. The lens is required to meet the use of sensors with pixel sizes of 5um and below.

[0007] 5. The overall size of the TOF and high-resolution time-of-flight measurement lenses on the current market is relatively large, which is not in line with market demand. Summary of the invention

[0008] The object of the present invention is to provide a high-resolution time-of-flight measurement lens with large light flux to solve at least one of the above problems.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] A high-resolution time-of-flight measurement lens with large light flux comprises a first lens to a sixth lens in sequence along an optical axis from an object side to an image side; each of the first lens to the sixth lens comprises an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through;

[0011] The first lens has a negative refractive power, and the object side surface of the first lens is convex, and the image side surface is concave;

[0012] The second lens has a negative refractive power, and the object side surface of the second lens is a convex surface, and the image side surface is a concave surface;

[0013] The third lens has positive refractive power, the object side surface of the third lens is convex, and the image side surface is convex or flat;

[0014] The fourth lens has positive refractive power, and the object side surface of the fourth lens is concave, and the image side surface is convex;

[0015] The fifth lens has positive refractive power, and the object side surface and image side surface of the fifth lens are convex;

[0016] The sixth lens has negative refractive power, the object side surface of the sixth lens is convex or flat, and the image side surface is concave.

[0017] The optical imaging lens has only the above-mentioned six lenses having refractive powers.

[0018] Preferably, the following condition is met: 1.7≤nd2≤nd1, wherein nd1 is the refractive index of the first lens, and nd2 is the refractive index of the second lens.

[0019] Preferably, a refractive index of the third lens is not less than refractive indexes of the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens.

[0020] Preferably, the following condition is met: 1.51≤nd2≤nd1≤nd3, wherein nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens.

[0021] Preferably, it further comprises an aperture, wherein the aperture is arranged between the third lens and the fourth lens.

[0022] Preferably, the fourth lens is an aspherical glass lens.

[0023] Preferably, the following condition is met: 2.5≤EFLX4 / EFL≤3.3, wherein EFLX4 is the focal length of the fourth lens, and EFL is the focal length of the system.

[0024] Preferably, a refractive index of the sixth lens is not greater than refractive indexes of the first lens, the second lens, the third lens, the fourth lens and the fifth lens.

[0025] Preferably, the following condition is met: 1.49≤nd6≤nd5≤2.1, wherein nd5 is the refractive index of the fifth lens, and nd6 is the refractive index of the sixth lens.

[0026] Preferably, the following condition is met: TTL≤15mm, BFL≥2mm, wherein TTL is the distance from the object side of the first lens to the imaging plane on the optical axis, and BFL is the distance from the center of the sixth lens to the imaging plane on the optical axis.

[0027] After adopting the above technical solution, the present invention has the following advantages compared with the background technology:

[0028] 1. The FNO of the present invention reaches below 1.2, and the field of view angle exceeds 135°, which can improve signal utilization and increase recognition range.

[0029] 2. The present invention controls TOF distortion and reduces the loss of effective pixels caused by distortion.

[0030] 3. Aiming at TOF application requirements, the present invention controls the relative illumination to ensure uniform relative illumination under high light conditions.

[0031] 4. The optical transfer function of the present invention is well controlled, and the resolution reaches the high-resolution level in the TOF field, which can meet the resolution requirements of the next generation of TOF sensors (940nm, pixel size below 3um). At the same time, for existing conventional TOF sensors, the design yield reaches more than 95%.

[0032] 5. The present invention uses a glass aspheric surface, which can increase the effective light transmission, reduce system distortion, and shorten the total length of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural schematic diagram of embodiment 1;

[0034] Figure 2 This is the MTF curve of the lens in Example 1 at a light wavelength of 925nm-960nm;

[0035] Figure 3 This is a defocus curve diagram of the lens in Example 1 at a light wavelength of 925nm-960nm;

[0036] Figure 4 The field curvature and distortion diagram of the lens in Example 1 at a light wavelength of 925nm-960nm;

[0037] Figure 5 This is a relative illumination diagram of the lens in Example 1 at a light wavelength of 950nm;

[0038] Figure 6 It is a structural schematic diagram of the second embodiment;

[0039] Figure 7 This is the MTF curve of the lens in Example 2 at a light wavelength of 925nm-960nm;

[0040] Figure 8 This is a defocus curve diagram of the lens in Example 2 at a light wavelength of 925nm-960nm;

[0041] Fig. 9 The field curvature and distortion diagram of the lens in Example 2 at a light wavelength of 925nm-960nm;

[0042] Fig.10 This is a relative illumination diagram of the lens in Example 2 at a light wavelength of 950nm;

[0043] Fig.11 This is a schematic diagram of the structure of Embodiment 3;

[0044] Fig.12 This is the MTF curve of the lens in Example 3 at a light wavelength of 925nm-960nm;

[0045] Fig.13 This is a defocus curve diagram of the lens in Example 3 at a light wavelength of 925nm-960nm;

[0046] Fig.14 The field curvature and distortion diagram of the lens in Example 3 at a light wavelength of 925nm-960nm;

[0047] Fig.15 This is a relative illumination diagram of the lens in Example 3 at a light wavelength of 950nm;

[0048] Fig.16 It is a structural schematic diagram of Embodiment 4;

[0049] Fig.17 This is the MTF curve of the lens in Example 4 at a light wavelength of 925nm-960nm;

[0050] Fig.18 This is a defocus curve diagram of the lens in Example 4 at a light wavelength of 925nm-960nm;

[0051] Fig.19 The field curvature and distortion diagram of the lens in Example 4 at a light wavelength of 925nm-960nm;

[0052] Fig. 20 This is a relative illumination diagram of the lens in Example 4 at a light wavelength of 950nm;

[0053] Fig.21 This is a schematic diagram of the structure of Embodiment 5;

[0054] Fig. 22 This is the MTF curve of the lens in Example 5 at a light wavelength of 925nm-960nm;

[0055] Fig.23 This is a defocus curve diagram of the lens in Example 5 at a light wavelength of 925nm-960nm;

[0056] Fig.24 The field curvature and distortion diagram of the lens in Example 5 at a light wavelength of 925nm-960nm;

[0057] Fig.25 This is a relative illumination diagram of the lens in Example 5 at a light wavelength of 950nm.

[0058] Description of reference numerals:

[0059] A first lens 1 , a second lens 2 , a third lens 3 , a fourth lens 4 , a fifth lens 5 , a sixth lens 6 , an aperture 7 , and a protective sheet 8 . DETAILED DESCRIPTION

[0060] To further illustrate the various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, a person of ordinary skill in the art should be able to understand other possible implementations and advantages of the present invention. The components in the figures are not drawn to scale, and similar component symbols are generally used to represent similar components.

[0061] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0062] In this specification, "a lens having a positive refractive power (or a negative refractive power)" means that the paraxial refractive power of the lens calculated by Gaussian optical theory is positive (or negative). The "object side (or image side) of the lens" is defined as a specific range of the lens surface through which the imaging light passes. The concave and convex shape of the lens can be judged according to the judgment method of ordinary knowledge in this field, that is, the concave and convex shape of the lens surface can be judged by the positive and negative signs of the radius of curvature (abbreviated as R value). R value can be commonly used in optical design software, such as Zemax or CodeV. R value is also commonly found in the lens data sheet (lensdatasheet) of optical design software. For the object side, when the R value is positive, the object side is judged to be convex; when the R value is negative, the object side is judged to be concave. Conversely, for the image side, when the R value is positive, the image side is judged to be concave; when the R value is negative, the image side is judged to be convex.

[0063] The present invention discloses a high-resolution time-of-flight measurement lens with large light flux, which includes a first lens to a sixth lens in sequence along an optical axis from the object side to the image side; the first lens to the sixth lens each include an object side surface facing the object side and allowing imaging light to pass through, and an image side surface facing the image side and allowing imaging light to pass through;

[0064] The first lens has a negative refractive power, and the object side surface of the first lens is convex, and the image side surface is concave;

[0065] The second lens has a negative refractive power, and the object side surface of the second lens is a convex surface, and the image side surface is a concave surface;

[0066] The third lens has positive refractive power, the object side surface of the third lens is convex, and the image side surface is convex or flat;

[0067] The fourth lens has positive refractive power, and the object side surface of the fourth lens is concave, and the image side surface is convex;

[0068] The fifth lens has positive refractive power, and the object side surface and image side surface of the fifth lens are convex;

[0069] The sixth lens has negative refractive power, the object side surface of the sixth lens is convex or flat, and the image side surface is concave.

[0070] The optical imaging lens has only the above-mentioned six lenses having refractive powers.

[0071] The first lens and the second lens are both negative lenses. Compared with a single front group negative lens, the aberration compensation of the rear group can be reduced, and the negative front group can be split into two or even three pieces, so as to reduce the focal length of each lens, reduce the primary amount of aberrations such as coma and distortion, and also reduce the high-order amount of aberrations. Under the current structure, if it is necessary to further expand the field of view, relative aperture and working distance, the curvature of the first lens and the second lens can be increased or a single negative lens can be separated to share the focal length.

[0072] Preferably, the following condition is met: 1.7≤nd2≤nd1, wherein nd1 is the refractive index of the first lens, and nd2 is the refractive index of the second lens. In terms of material selection, since the system has low requirements for chromatic aberration correction, in order to compress the total length of the system and reduce the difficulty of lens manufacturing, flint glass with a refractive index lower than 1.7 is used.

[0073] Preferably, the refractive index of the third lens is not less than the refractive indexes of the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens. The third lens is a biconvex or plano-convex lens, which reduces the height of the light passing through the first lens and the second lens, corrects the spherical aberration caused by the negative lens group, and has the highest refractive index in the entire optical system.

[0074] Preferably, the following condition is met: 1.51≤nd2≤nd1≤nd3, wherein nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens.

[0075] Preferably, it further comprises an aperture, wherein the aperture is arranged between the third lens and the fourth lens.

[0076] Preferably, the fourth lens is an aspherical glass lens. The fourth lens is responsible for correcting the residual aberration of the front group. The basic appearance is a thick meniscus lens, which can improve high-order spherical aberration and coma, and increase the relative aperture to below 1.2. At the same time, the aspherical effective diameter can be minimized to reduce the system cost.

[0077] The equations for the object-side and image-side curves of a glass aspheric lens are expressed as follows:

[0078]

[0079] in:

[0080] z: Depth of the aspherical surface (the vertical distance between the point on the aspherical surface that is y away from the optical axis and the tangent plane that is tangent to the vertex on the optical axis of the aspherical surface);

[0081] c: the vertex curvature of the aspherical surface;

[0082] K: Conic Constant;

[0083] radial distance;

[0084] r n : Normalization radius (NRADIUS);

[0085] u:r / r n ;

[0086] a m : mth order Q con coefficient (the mth Qcon coefficient);

[0087] Q m con : mth order Q con polynomial (the mth Qcon polynomial).

[0088] Preferably, the following condition is met: 2.5≤EFLX4 / EFL≤3.3, wherein EFLX4 is the focal length of the fourth lens, and EFL is the focal length of the system.

[0089] Preferably, the refractive index of the sixth lens is not greater than the refractive indexes of the first lens, the second lens, the third lens, the fourth lens and the fifth lens. The fifth lens is a double convex or plano-convex lens, which is approximately a drum-type lens. The refractive index of the lens in a large aperture system needs to be increased to reduce the light height at this position. The sixth lens is a meniscus negative lens, which is combined with the fifth lens positive and negative lenses to correct aberrations. It is approximately a meniscus thick lens, which can reduce the field curvature of the system, improve assembly conditions, and increase product yield. This type of small target surface system often has a large main light incidence angle. In order to match the main light distribution, the image side of the sixth lens meniscus negative lens is concave and has the lowest refractive index in the entire optical system.

[0090] Preferably, the following condition is met: 1.49≤nd6≤nd5≤2.1, wherein nd5 is the refractive index of the fifth lens, and nd6 is the refractive index of the sixth lens.

[0091] Preferably, the following condition is met: TTL≤15mm, BFL≥2mm, wherein TTL is the distance from the object side of the first lens to the imaging plane on the optical axis, and BFL is the distance from the center of the sixth lens to the imaging plane on the optical axis.

[0092] The time-of-flight measurement lens of the present invention will be described in detail below with reference to specific embodiments.

[0093] Embodiment 1

[0094] refer to Figure 1 As shown, this embodiment discloses a high-resolution time-of-flight measurement lens with large light flux, which includes a first lens 1 to a sixth lens 6 in sequence along an optical axis from the object side to the image side; each of the first lens 1 to the sixth lens 6 includes an object-side surface facing the object side and allowing imaging light to pass through, and an image-side surface facing the image side and allowing imaging light to pass through;

[0095] The first lens 1 has a negative refractive power, and the object side surface of the first lens 1 is a convex surface, and the image side surface is a concave surface;

[0096] The second lens 2 has a negative refractive power, and the object side surface of the second lens 2 is a convex surface, and the image side surface is a concave surface;

[0097] The third lens 3 has positive refractive power, the object side surface of the third lens 3 is convex, and the image side surface is convex or flat;

[0098] The fourth lens 4 has a positive refractive power, and the object side surface of the fourth lens 4 is a concave surface, and the image side surface is a convex surface;

[0099] The fifth lens element 5 has a positive refractive power, and the object side surface and the image side surface of the fifth lens element 5 are convex;

[0100] The sixth lens element 6 has a negative refractive power, and the object side surface of the sixth lens element 6 is a convex surface or a flat surface, and the image side surface is a concave surface.

[0101] In this embodiment, the aperture 7 is disposed between the third lens 3 and the fourth lens 4. Of course, in other embodiments, the aperture 7 may also be disposed at other appropriate positions.

[0102] The detailed optical data of this specific embodiment are shown in Table 1.

[0103] Table 1 Detailed optical data of Example 1

[0104] Surface number surface Radius of curvature thickness Material Refractive Index Dispersion coefficient focal length Semi-caliber # Type R TC Glass nd vd EFLX SD 0 Subject surface INF 1000 2477.8 1 First lens 24.496 0.700 H-ZLAF4LA 1.91 35.3 -4.6 4.3 2 3.437 0.983 2.9 3 Second lens 6.161 0.599 H-ZBAF21 1.72 38.0 -12.6 2.9 4 3.491 2.545 2.5 5 The third lens 5.728 1.800 H-ZLAF90 2.00 25.4 5.9 2.5 6 INF 1.251 2.2 7 Aperture INF 0.355 1.6 8 The fourth lens -35.440 1.800 D-ZLAF52LA 1.81 41.0 5.0 1.6 9 -3.657 0.080 2.1 10 Fifth lens 27.842 1.800 H-ZLAF4LA 1.91 35.3 5.6 2.2 11 -5.831 0.080 2.2 12 The sixth lens 62.826 0.509 H-QK3L 1.49 70.4 -7.6 2.1 13 3.430 0.790 1.9 14 plate glass INF 0.210 H-K9L 1.52 64.2 Infinity 1.9 15 INF 1.306 1.9 16 Imaging surface INF 0.000 2.0

[0105] In this specific embodiment, the fourth lens 4 is a glass aspheric lens. For detailed parameter data of the aspheric surface of the fourth lens 4, please refer to the following table:

[0106] Surface serial number K A4 A6 A8 A10 A12 A14 S8 1.09E+02 -1.42E-02 1.00E-03 -1.13E-03 1.31E-04 1.05E-04 -2.74E-05 S9 -3.75E-01 -4.26E-04 -2.13E-04 -3.44E-05 1.65E-05 -3.47E-06 3.03E-07

[0107] In this specific embodiment, the focal length of the optical imaging lens is EFL=1.800 mm; FOV=136°, the image height is 4 mm, TTL=14.81 mm, BFL=2.31 mm, and the transmittance is F / 1.2.

[0108] Please refer to the structural diagram of the optical imaging lens in this specific embodiment. Figure 1 Please refer to the MTF curve of the lens at a wavelength of 925nm-960nm Figure 2 From the figure, we can see that when the spatial frequency of this lens reaches 150lp / mm, the full field transfer function image is still greater than 30%, the center to edge uniformity is high, the imaging quality is excellent, and the lens resolution is high. For the defocus curve of the lens at a wavelength of 925nm-960nm, please refer to Figure 3 , it can be seen from the figure that the lens has a small defocus under visible light. For the field curvature / distortion of the lens under the wavelength of 925nm-960nm, please refer to Figure 4 From the figure, we can see that the optical distortion is controlled within -6%, the image frame will not be obviously deformed, the image restoration is relatively accurate, the image quality is high, and there is no need for post-image algorithm to correct the distortion, which is convenient for application. For the relative illumination diagram of the lens at a wavelength of 950nm, please refer to Figure 5 As can be seen from the figure, the relative illumination is greater than 70%, which provides a relatively uniform illumination for the image surface and ensures uniform relative illumination under large light and large angle conditions.

[0109] Embodiment 2

[0110] Cooperate Figures 6 to 10As shown, the surface profile and refractive power of each lens in this embodiment and the first embodiment are substantially the same, but the optical parameters such as the curvature radius of each lens surface and lens thickness are different.

[0111] The detailed optical data of this specific embodiment are shown in Table 2.

[0112] Table 2 Detailed optical data of Example 2

[0113]

[0114]

[0115] In this specific embodiment, the fourth lens 4 is a glass aspheric lens. For detailed parameter data of the aspheric surface of the fourth lens 4, please refer to the following table:

[0116] Surface serial number K A4 A6 A8 A10 A12 A14 S8 1.09E+02 -1.42E-02 1.00E-03 -1.13E-03 1.31E-04 1.05E-04 -2.74E-05 S9 -3.75E-01 -4.26E-04 -2.13E-04 -3.44E-05 1.65E-05 -3.47E-06 3.03E-07

[0117] In this specific embodiment, the focal length of the optical imaging lens is EFL=1.800 mm; FOV=136°, the image height is 4 mm, TTL=14.81 mm, BFL=2.31 mm, and the transmittance is F / 1.2.

[0118] Please refer to the structural diagram of the optical imaging lens in this specific embodiment. Figure 6 Please refer to the MTF curve of the lens at a wavelength of 925nm-960nm Figure 7 From the figure, we can see that when the spatial frequency of this lens reaches 150lp / mm, the full field transfer function image is still greater than 30%, the center to edge uniformity is high, the imaging quality is excellent, and the lens resolution is high. For the defocus curve of the lens at a wavelength of 925nm-960nm, please refer to Figure 8 , it can be seen from the figure that the lens has a small defocus under visible light. For the field curvature / distortion of the lens under the wavelength of 925nm-960nm, please refer to Fig. 9 From the figure, we can see that the optical distortion is controlled within -6%, the image frame will not be obviously deformed, the image restoration is relatively accurate, the image quality is high, and there is no need for post-image algorithm to correct the distortion, which is convenient for application. For the relative illumination diagram of the lens at a wavelength of 950nm, please refer to Fig.10 As can be seen from the figure, the relative illumination is greater than 70%, which provides a relatively uniform illumination for the image surface and ensures uniform relative illumination under large light and large angle conditions.

[0119] Embodiment 3

[0120] Cooperate Figures 11 to 15 As shown, the surface profile and refractive power of each lens in this embodiment and the first embodiment are substantially the same, but the optical parameters such as the curvature radius of each lens surface and lens thickness are different.

[0121] The detailed optical data of this specific embodiment are shown in Table 3.

[0122] Table 3 Detailed optical data of Example 3

[0123] Surface number surface Radius of curvature thickness Material Refractive Index Dispersion coefficient focal length Semi-caliber # Type R TC Glass nd vd EFLX SD 0 Subject surface INF 1000 2465.7 1 First lens 17.993 0.700 H-ZLAF4LA 1.91 35.3 -4.3 4.3 2 3.086 1.285 2.8 3 Second lens 6.227 0.800 H-ZBAF21 1.72 38.0 -11.4 2.8 4 3.321 1.936 2.3 5 The third lens 6.274 1.630 H-ZLAF90 2.00 25.4 6.0 2.5 6 -75.106 1.712 2.3 7 Aperture INF 0.132 1.7 8 The fourth lens 16.203 1.600 D-ZLAF52LA 1.81 41.0 5.8 1.7 9 -6.153 0.100 2.0 10 Fifth lens 27.851 1.944 H-ZLAF4LA 1.91 35.3 5.8 2.1 11 -6.131 0.100 2.2 12 The sixth lens 6.969 0.700 H-QK3L 1.49 70.4 -13.0 2.1 13 3.183 0.790 1.9 14 plate glass INF 0.210 H-K9L 1.52 64.2 Infinity 1.9 15 INF 1.218 1.9 16 Imaging surface INF 0.000 2.0

[0124] In this specific embodiment, the fourth lens 4 is a glass aspheric lens. For detailed parameter data of the aspheric surface of the fourth lens 4, please refer to the following table:

[0125] Surface serial number K A4 A6 A8 A10 A12 A14 S8 5.33E+01 -1.09E-02 3.39E-03 -9.22E-04 -1.41E-04 9.11E-05 -1.02E-05 S9 -1.96E+00 1.61E-03 -2.09E-04 5.74E-05 1.62E-05 -1.02E-05 1.25E-06

[0126] In this specific embodiment, the focal length of the optical imaging lens is EFL=1.770 mm; FOV=136°, the image height is 4 mm, TTL=14.86 mm, BFL=2.22 mm, and the transmittance is F / 1.2.

[0127] Please refer to the structural diagram of the optical imaging lens in this specific embodiment. Fig.11 Please refer to the MTF curve of the lens at a wavelength of 925nm-960nm Fig.12 From the figure, we can see that when the spatial frequency of this lens reaches 150lp / mm, the full field transfer function image is still close to 30%, the center to edge uniformity is high, the imaging quality is excellent, and the lens resolution is high. For the defocus curve of the lens at a wavelength of 925nm-960nm, please refer to Fig.13 , it can be seen from the figure that the lens has a small defocus under visible light. For the field curvature / distortion of the lens under the wavelength of 925nm-960nm, please refer to Fig.14 From the figure, we can see that the optical distortion is controlled within -6%, the image frame will not be obviously deformed, the image restoration is relatively accurate, the image quality is high, and there is no need for post-image algorithm to correct the distortion, which is convenient for application. For the relative illumination diagram of the lens at a wavelength of 950nm, please refer to Fig.15 As can be seen from the figure, the relative illumination is greater than 70%, which provides a relatively uniform illumination for the image surface and ensures uniform relative illumination under large light and large angle conditions.

[0128] Embodiment 4

[0129] Cooperate Figures 16 to 20 As shown, the surface profile and refractive power of each lens in this embodiment and the first embodiment are substantially the same, but the optical parameters such as the curvature radius of each lens surface and lens thickness are different.

[0130] The detailed optical data of this specific embodiment are shown in Table 4.

[0131] Table 4 Detailed optical data of Example 4

[0132] Surface number surface Radius of curvature thickness Material Refractive Index Dispersion coefficient focal length Semi-caliber # Type R TC Glass nd vd EFLX SD 0 Subject surface INF 1000 2479.0 1 First lens 24.547 0.690 H-ZLAF50E 1.80 46.6 -4.5 4.4 2 3.084 1.556 2.8 3 Second lens 12.000 0.702 H-ZBAF21 1.72 38.0 -7.9 2.8 4 3.716 1.296 2.4 5 The third lens 5.497 1.732 H-ZLAF90 2.00 25.4 5.2 2.6 6 -51.113 1.871 2.4 7 Aperture INF 0.250 1.6 8 The fourth lens -246.972 1.798 D-ZLAF52LA 1.81 41.0 4.5 1.7 9 -3.551 0.100 2.1 10 Fifth lens 34.462 1.810 H-ZBAF21 1.72 38.0 6.0 2.2 11 -4.719 0.100 2.3 12 The sixth lens 41.578 0.597 H-QK3L 1.49 70.4 -8.0 2.1 13 3.505 0.790 1.9 14 plate glass INF 0.210 H-K9L 1.52 64.2 Infinity 1.9 15 INF 1.208 1.9 16 Imaging surface INF 0.000 2.0

[0133] In this specific embodiment, the fourth lens 4 is a glass aspheric lens. For detailed parameter data of the aspheric surface of the fourth lens 4, please refer to the following table:

[0134] Surface serial number K A4 A6 A8 A10 A12 A14 S8 -1.00E+02 -1.32E-02 -2.94E-04 -3.99E-04 7.56E-05 2.28E-05 -9.38E-06 S9 -5.75E-01 -1.56E-04 -5.13E-04 2.61E-05 1.41E-05 -5.39E-06 5.24E-07

[0135] In this specific embodiment, the focal length of the optical imaging lens is EFL=1.810 mm; FOV=136°, image height is 4 mm, TTL=14.71 mm, BFL=2.21 mm, and the transmittance is F / 1.2.

[0136] Please refer to the structural diagram of the optical imaging lens in this specific embodiment. Fig.16 Please refer to the MTF curve of the lens at a wavelength of 925nm-960nm Fig.17 From the figure, we can see that when the spatial frequency of this lens reaches 150lp / mm, the full field transfer function image is still greater than 30%, the center to edge uniformity is high, the imaging quality is excellent, and the lens resolution is high. For the defocus curve of the lens at a wavelength of 925nm-960nm, please refer to Fig.18 , it can be seen from the figure that the lens has a small defocus under visible light. For the field curvature / distortion of the lens under the wavelength of 925nm-960nm, please refer to Fig.19 From the figure, we can see that the optical distortion is controlled within -6%, the image frame will not be obviously deformed, the image restoration is relatively accurate, the image quality is high, and there is no need for post-image algorithm to correct the distortion, which is convenient for application. For the relative illumination diagram of the lens at a wavelength of 950nm, please refer to Fig. 20 As can be seen from the figure, the relative illumination is greater than 70%, which provides a relatively uniform illumination for the image surface and ensures uniform relative illumination under large light and large angle conditions.

[0137] Embodiment 5

[0138] Cooperate Figure 21 to Figure 25 As shown, the surface profile and refractive power of each lens in this embodiment and the first embodiment are substantially the same, but the optical parameters such as the curvature radius of each lens surface and lens thickness are different.

[0139] The detailed optical data of this specific embodiment are shown in Table 5.

[0140] Table 5 Detailed optical data of Example 5

[0141] Surface number surface Radius of curvature thickness Material Refractive Index Dispersion coefficient focal length Semi-caliber # Type R TC Glass nd vd EFLX SD 0 Subject surface INF 1000 2477.4 1 First lens 21.772 0.700 H-ZLAF4LA 1.91 35.3 -4.6 4.3 2 3.409 1.074 2.9 3 Second lens 6.083 0.650 H-ZBAF21 1.72 38.0 -11.6 2.9 4 3.331 2.447 2.4 5 The third lens 5.643 1.819 H-ZLAF90 2.00 25.4 5.8 2.5 6 INF 1.190 2.2 7 Aperture INF 0.327 1.6 8 The fourth lens -37.932 1.800 D-ZLAF52LA 1.81 41.0 5.7 1.7 9 -4.144 0.080 2.1 10 Fifth lens 20.755 1.800 H-ZLAF4LA 1.91 35.3 5.6 2.2 11 -6.249 0.080 2.3 12 The sixth lens 12.692 0.600 H-QK3L 1.49 70.4 -9.5 2.1 13 3.313 0.790 1.9 14 plate glass INF 0.210 H-K9L 1.52 64.2 Infinity 1.9 15 INF 1.289 2.0 16 Imaging surface INF 0.000 2.0

[0142] In this specific embodiment, the fourth lens 4 is a glass aspheric lens. For detailed parameter data of the aspheric surface of the fourth lens 4, please refer to the following table:

[0143] Surface serial number K A4 A6 A8 A10 A12 A14 S8 6.52E+01 -1.26E-02 1.44E-03 -7.66E-04 5.44E-05 4.00E-05 -7.17E-06 S9 -3.54E-01 -1.75E-04 -3.87E-05 -4.15E-05 1.52E-05 -2.16E-06 1.90E-07

[0144] In this specific embodiment, the focal length of the optical imaging lens is EFL=1.800 mm; FOV=136°, the image height is 4 mm, TTL=14.61 mm, BFL=2.29 mm, and the transmittance is F / 1.2.

[0145] Please refer to the structural diagram of the optical imaging lens in this specific embodiment. Fig.21 Please refer to the MTF curve of the lens at a wavelength of 925nm-960nm Fig. 22 From the figure, we can see that when the spatial frequency of this lens reaches 150lp / mm, the full field transfer function image is still greater than 30%, the center to edge uniformity is high, the imaging quality is excellent, and the lens resolution is high. For the defocus curve of the lens at a wavelength of 925nm-960nm, please refer to Fig.23 , it can be seen from the figure that the lens has a small defocus under visible light. For the field curvature / distortion of the lens under the wavelength of 925nm-960nm, please refer to Fig.24 From the figure, we can see that the optical distortion is controlled within -6%, the image frame will not be obviously deformed, the image restoration is relatively accurate, the image quality is high, and there is no need for post-image algorithm to correct the distortion, which is convenient for application. For the relative illumination diagram of the lens at a wavelength of 950nm, please refer to Fig.25 As can be seen from the figure, the relative illumination is greater than 70%, which provides a relatively uniform illumination for the image surface and ensures uniform relative illumination under large light and large angle conditions.

[0146] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A high-resolution time-of-flight measurement lens with large light flux, characterized in that: The lens system includes a first lens to a sixth lens in sequence along an optical axis from the object side to the image side; each of the first lens to the sixth lens includes an object-side surface facing the object side and allowing imaging light to pass therethrough, and an image-side surface facing the image side and allowing imaging light to pass therethrough; The first lens has a negative refractive power, and the object side surface of the first lens is convex, and the image side surface is concave; The second lens has a negative refractive power, and the object side surface of the second lens is a convex surface, and the image side surface is a concave surface; The third lens has positive refractive power, the object side surface of the third lens is convex, and the image side surface is convex or flat; The fourth lens has positive refractive power, and the object side surface of the fourth lens is concave, and the image side surface is convex; The fifth lens has positive refractive power, and the object side surface and image side surface of the fifth lens are convex; The sixth lens has a negative refractive power, and the object side surface of the sixth lens is a convex surface, and the image side surface is a concave surface; Among them, 2.5≤EFLX4 / EFL≤3.3, wherein EFLX4 is the focal length value of the fourth lens, and EFL is the focal length value of the high-throughput high-resolution time-of-flight measurement lens; the high-throughput high-resolution time-of-flight measurement lens has only the above-mentioned six lenses with refractive power.

2. A high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The following condition is met: 1.72≤nd2≤nd1≤1.91, wherein nd1 is the refractive index of the first lens, and nd2 is the refractive index of the second lens.

3. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The refractive index of the third lens is not less than the refractive indexes of the first lens, the second lens, the fourth lens, the fifth lens and the sixth lens.

4. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 3, characterized in that: The following condition is met: 1.72≤nd2≤nd1≤nd3≤2, wherein nd1 is the refractive index of the first lens, nd2 is the refractive index of the second lens, and nd3 is the refractive index of the third lens.

5. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The lens also includes an aperture stop, which is disposed between the third lens and the fourth lens.

6. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The fourth lens is an aspherical glass lens.

7. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The refractive index of the sixth lens is not greater than the refractive indexes of the first lens, the second lens, the third lens, the fourth lens and the fifth lens.

8. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 7, characterized in that: The following condition is met: 1.49≤nd6≤nd5≤2.1, wherein nd5 is the refractive index of the fifth lens, and nd6 is the refractive index of the sixth lens.

9. The high-resolution time-of-flight measurement lens with large light flux as claimed in claim 1, characterized in that: The following conditions are met: 14.61≤TTL≤14.86mm, 2.31mm≥BFL≥2.21mm, wherein TTL is the distance from the object side of the first lens to the imaging plane on the optical axis, and BFL is the distance from the center of the sixth lens to the imaging plane on the optical axis.

Images