Low-distortion telecentric projection lens for 3D structured light

Abstract

The application relates to a low-distortion telecentric projection lens for 3D structured light, which comprises, from left to right, a diverging lens group, a diaphragm, a converging lens group and an image plane; the diverging lens group comprises, from left to right, a first lens, a second lens and a third lens; and the converging lens group comprises, from left to right, a fourth lens, a fifth lens, a sixth lens and a seventh lens. The projection lens has the characteristics of high system resolution (up to 100 lp / mm or more), low system distortion rate (0.2% or less), simple structure (7 spherical lenses), low manufacturing cost, low distortion, high resolution and image plane telecentricity.

Description

Technical Field

[0001] This invention relates to the field of projection lens technology, and in particular to a low-distortion telecentric projection lens for 3D structured light. Background Technology

[0002] In recent years, with the rapid development of industrial inspection and automation, 3D measurement technology has been increasingly widely used in fields such as 3C electronics, automotive manufacturing, and aerospace. 3D structured light sensors utilize a grating projection device to project several specifically coded structured light beams onto the object under test. A camera positioned at a certain angle captures the structured light images projected onto the object, and subsequent image processing and algorithm calculations yield a 3D image of the object. The quality of the structured light image projected by the grating projection device directly affects the subsequent calculation of the object's 3D image, and the projection lens is crucial in determining the quality of the projected image.

[0003] To meet the evolving demands of 3D measurement technology, projection lenses must ensure high imaging quality across the entire optical system to improve the measurement accuracy of 3D structured light sensors. Existing projection lenses typically employ nine or more lenses, resulting in a complex lens structure. Alternatively, aspherical technology is used to simplify the structure or improve imaging quality; however, the difficulty in manufacturing and inspecting aspherical lenses increases the cost and complexity of the process.

[0004] In view of the above-mentioned shortcomings, the designer actively researched and innovated in order to create a low-distortion telecentric projection lens for 3D structured light, making it more valuable for industrial applications. Summary of the Invention

[0005] To address the aforementioned technical problems, the purpose of this invention is to provide a low-distortion telecentric projection lens for 3D structured light.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A low-distortion telecentric projection lens for 3D structured light, the projection lens comprising, from left to right, a diverging lens group, an aperture stop, a converging lens group and an image plane;

[0008] The diverging lens group, from left to right, includes the first lens, the second lens, and the third lens; the converging lens group, from left to right, includes the fourth lens, the fifth lens, the sixth lens, and the seventh lens.

[0009] The first lens is a meniscus lens with its concave surface facing the aperture stop; the second lens is a plano-convex lens with its convex surface facing the aperture stop; the third lens is a meniscus lens with its concave surface facing away from the aperture stop; the fourth lens is a biconcave lens; the fifth lens is a meniscus lens with its concave surface facing the aperture stop; the sixth lens is a plano-convex lens with its convex surface facing the image plane; and the seventh lens is a meniscus lens with its concave surface facing the image plane.

[0010] As a further improvement of the present invention, wherein,

[0011] The distance between the first lens and the second lens is between 3.5mm and 5.5mm;

[0012] The interval between the second and third lenses is between 26mm and 28mm;

[0013] The distance between the third lens and the aperture stop is between 0.5mm and 2.5mm;

[0014] The distance between the aperture stop and the fourth lens is between 2.5mm and 4.5mm;

[0015] The gap between the fourth and fifth lenses is between 0.5mm and 2.5mm;

[0016] The gap between the fifth and sixth lenses is between 0.5mm and 2.5mm;

[0017] The interval between the sixth and seventh lenses is between 11mm and 13mm;

[0018] The distance between the seventh lens and the image plane is between 22.5mm and 24.5mm.

[0019] As a further improvement of the present invention, wherein,

[0020] The distance between the first lens and the second lens is 4.5mm;

[0021] The distance between the second and third lenses is 27mm;

[0022] The distance between the third lens and the aperture stop is 1.5mm;

[0023] The distance between the aperture stop and the fourth lens is 3.5mm;

[0024] The interval between the fourth and fifth lenses is 1.5mm;

[0025] The interval between the fifth and sixth lenses is 1.5mm;

[0026] The interval between the sixth and seventh lenses is 12mm;

[0027] The distance between the seventh lens and the image plane is 23.5 mm.

[0028] As a further improvement of the present invention, the optical power of the first lens is negative, the optical power of the second lens is positive, the optical power of the third lens is positive, the optical power of the fourth lens is negative, the optical power of the fifth lens is positive, the optical power of the sixth lens is positive, and the optical power of the seventh lens is positive.

[0029] As a further improvement of the present invention, wherein,

[0030] The focal length of the first lens element is between -45mm and -55mm;

[0031] The focal length of the second lens is between 50mm and 60mm;

[0032] The focal length of the third lens is between 50mm and 60mm;

[0033] The focal length of the fourth lens element is between -5mm and -15mm;

[0034] The focal length of the fifth lens is between 30mm and 40mm;

[0035] The focal length of the sixth lens is between 20mm and 30mm;

[0036] The focal length of the seventh lens is between 55mm and 65mm.

[0037] As a further improvement of the present invention, wherein,

[0038] The focal length of the first lens is -50mm;

[0039] The focal length of the second lens is 55mm;

[0040] The focal length of the third lens is 55mm;

[0041] The focal length of the fourth lens is -10mm;

[0042] The focal length of the fifth lens is 35mm;

[0043] The focal length of the sixth lens is 25mm;

[0044] The focal length of the seventh lens is 60mm.

[0045] As a further improvement of the present invention, wherein,

[0046] The refractive index of the first lens is between 1.6 and 1.7;

[0047] The refractive index of the second lens is between 1.7 and 1.8;

[0048] The refractive index of the third lens is between 1.55 and 1.65;

[0049] The refractive index of the fourth lens is between 1.7 and 1.8;

[0050] The refractive index of the fifth lens is between 1.6 and 1.7;

[0051] The refractive index of the sixth lens is between 1.6 and 1.7;

[0052] The refractive index of the seventh lens is between 1.6 and 1.7.

[0053] As a further improvement of the present invention, wherein,

[0054] The refractive index of the first lens is 1.65;

[0055] The refractive index of the second lens is 1.75;

[0056] The refractive index of the third lens is 1.6;

[0057] The refractive index of the fourth lens is 1.75;

[0058] The refractive index of the fifth lens is 1.65;

[0059] The refractive index of the sixth lens is 1.65;

[0060] The refractive index of the seventh lens is 1.65.

[0061] As a further improvement of the present invention, the projection lens chip is a 0.45-inch DMD-DLP4500 chip with a resolution of 912*1140.

[0062] As a further improvement of the present invention, the effective focal length of the projection lens is 19.5mm, the relative numerical aperture is effective focal length / 2.4, the maximum aperture is less than 30mm, and the total optical length is 96.84mm.

[0063] By means of the above-described solution, the present invention has at least the following advantages:

[0064] This invention provides a low-distortion telecentric projection lens for 3D structured light, which features high definition, low distortion, simple structure, easy processing, and low cost.

[0065] The projection lens of this invention has a high system resolution, reaching over 100 lp / mm, and a low system distortion rate, below 0.2%. It uses 7 spherical lenses, has a simple structure, and features low manufacturing cost, low distortion, high resolution, and telecentric image.

[0066] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0067] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 This is a schematic diagram of the structure of a low-distortion telecentric projection lens for 3D structured light according to the present invention.

[0069] Figure 2 This is a table of structural parameters for the lens in this invention, where the unit is mm;

[0070] Figure 3 This is a ray dot pattern diagram when the half-field image height is 0, 0.707, and 1.0 in an embodiment of the present invention;

[0071] Figure 4 These are the MTF curves of the image transfer function at different fields of view in the embodiments of the present invention;

[0072] Figure 5 This is a field curvature and distortion diagram of the projection lens in an embodiment of the present invention.

[0073] The meanings of the labels in the figures are as follows.

[0074] 1. First lens 2. Second lens

[0075] 3 Third lens 4 Aperture

[0076] 5. Fourth lens 6. Fifth lens

[0077] 7. Sixth lens 8. Seventh lens

[0078] 9 Image plane Detailed Implementation

[0079] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0080] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0081] Example

[0082] like Figures 1-5 As shown,

[0083] A low-distortion telecentric projection lens for 3D structured light, the projection lens comprising, from left to right, a diverging lens group, an aperture stop 4, a converging lens group and an image plane 9;

[0084] The diverging lens group, from left to right, includes the first lens 1, the second lens 2, and the third lens 3, while the converging lens group, from left to right, includes the fourth lens 5, the fifth lens 6, the sixth lens 7, and the seventh lens 8.

[0085] The first lens 1 is a meniscus lens with its concave surface facing the aperture 4; the second lens 2 is a plano-convex lens with its convex surface facing the aperture 4; the third lens 3 is a meniscus lens with its concave surface facing away from the aperture 4; the fourth lens 5 is a biconcave lens; the fifth lens 6 is a meniscus lens with its concave surface facing the aperture 4; the sixth lens 7 is a plano-convex lens with its convex surface facing the image plane 9; and the seventh lens 8 is a meniscus lens with its concave surface facing the image plane 9.

[0086] Preferably, among which,

[0087] The distance between the first lens 1 and the second lens 2 is between 3.5mm and 5.5mm;

[0088] The interval between the second lens 2 and the third lens 3 is between 26mm and 28mm;

[0089] The distance between the third lens 3 and the aperture 4 is between 0.5mm and 2.5mm;

[0090] The distance between aperture 4 and the fourth lens 5 is between 2.5mm and 4.5mm;

[0091] The gap between the fourth lens 5 and the fifth lens 6 is between 0.5mm and 2.5mm;

[0092] The interval between the fifth lens 6 and the sixth lens 7 is between 0.5mm and 2.5mm;

[0093] The interval between the sixth lens 7 and the seventh lens 8 is between 11mm and 13mm;

[0094] The distance between the seventh lens 8 and the image plane 9 is between 22.5 mm and 24.5 mm.

[0095] Preferably, among which,

[0096] The distance between the first lens 1 and the second lens 2 is 4.5mm;

[0097] The interval between the second lens 2 and the third lens 3 is 27mm;

[0098] The distance between the third lens 3 and the aperture 4 is 1.5mm;

[0099] The distance between aperture 4 and the fourth lens 5 is 3.5mm;

[0100] The interval between the fourth lens 5 and the fifth lens 6 is 1.5mm;

[0101] The interval between the fifth lens 6 and the sixth lens 7 is 1.5mm;

[0102] The interval between the sixth lens 7 and the seventh lens 8 is 12mm;

[0103] The distance between the seventh lens 8 and the image plane 9 is 23.5 mm.

[0104] Preferably, the optical power of the first lens 1 is negative, the optical power of the second lens 2 is positive, the optical power of the third lens 3 is positive, the optical power of the fourth lens 5 is negative, the optical power of the fifth lens 6 is positive, the optical power of the sixth lens 7 is positive, and the optical power of the seventh lens 8 is positive.

[0105] Preferably, among which,

[0106] The focal length of the first lens 1 is between -45mm and -55mm;

[0107] The focal length of the second lens 2 is between 50mm and 60mm;

[0108] The focal length of the third lens 3 is between 50mm and 60mm;

[0109] The focal length of the fourth lens element 5 is between -5mm and -15mm;

[0110] The focal length of the fifth lens 6 is between 30mm and 40mm;

[0111] The focal length of the sixth lens 7 is between 20mm and 30mm;

[0112] The focal length of the seventh lens 8 is between 55mm and 65mm.

[0113] Preferably, among which,

[0114] The focal length of the first lens 1 is -50mm;

[0115] The focal length of the second lens 2 is 55mm;

[0116] The focal length of the third lens 3 is 55mm;

[0117] The focal length of the fourth lens element 5 is -10mm;

[0118] The focal length of the fifth lens 6 is 35mm;

[0119] The focal length of the sixth lens element 7 is 25mm;

[0120] The focal length of the seventh lens, 8, is 60mm.

[0121] Preferably, among which,

[0122] The refractive index of the first lens 1 is between 1.6 and 1.7;

[0123] The refractive index of the second lens 2 is between 1.7 and 1.8;

[0124] The refractive index of the third lens 3 is between 1.55 and 1.65;

[0125] The refractive index of the fourth lens 5 is between 1.7 and 1.8;

[0126] The refractive index of the fifth lens 6 is between 1.6 and 1.7;

[0127] The refractive index of the sixth lens 7 is between 1.6 and 1.7;

[0128] The refractive index of the seventh lens 8 is between 1.6 and 1.7.

[0129] Preferably, among which,

[0130] The refractive index of the first lens 1 is 1.65;

[0131] The refractive index of the second lens 2 is 1.75;

[0132] The refractive index of the third lens 3 is 1.6;

[0133] The refractive index of the fourth lens 5 is 1.75;

[0134] The refractive index of the fifth lens 6 is 1.65;

[0135] The refractive index of the sixth lens 7 is 1.65;

[0136] The refractive index of the seventh lens, 8, is 1.65.

[0137] Preferably, the projection lens uses a 0.45-inch DMD-DLP4500 chip with a resolution of 912*1140.

[0138] Preferably, the projection lens has an effective focal length of 19.5mm, a relative numerical aperture of effective focal length / 2.4, a maximum aperture of less than 30mm, and a total optical length of 96.84mm. The total optical length is the distance from the first lens 1 to the image plane 9.

[0139] This invention relates to a low-distortion telecentric projection lens for 3D structured light. The projection lens comprises two lens groups: a first diverging lens group with negative optical power, and a second converging lens group with positive optical power, with an aperture stop 4 located between the two lens groups. The diverging lens group sequentially includes a first lens 1, a second lens 2, and a third lens 3, and the converging lens group sequentially includes a fourth lens 5, a fifth lens 6, a sixth lens 7, and a seventh lens 8.

[0140] An embodiment of the present invention:

[0141] In this embodiment, the wavelength is WAVE, the aperture number is FNO, the effective focal length is EFL, and the distance from the first lens 1 to the image plane 9 is TOTR. For the 3D structured light projection lens of this invention, the light source is blue light with a center wavelength of 460nm, WAVE = 440nm-460nm-480nm, FNO = 2.4, EFL = 19.5mm, and TOTR = 96.84mm.

[0142] The following is a table of structural parameters for the lens, in mm.

[0143] Surf Radius Thickness Glass 1 2009.580 1.730 1.66，54.7 2 33.488 4.528 3 Infinity 3.000 1.76，27.6 4 -44.555 27.314 5 -40.782 5.500 1.61，58.9 6 -19.227 1.324 STO infinity 3.498 8 -8.810 1.650 1.76，27.6 9 201.302 1.557 10 -26.396 3.400 1.66，54.7 11 -13.391 0.554 12 -1168.981 4.480 1.66，54.7 13 -16.199 12.259 14 29.079 2.600 1.66，54.7 15 93.200 23.448 IMA infinity

[0144] Figure 3 The figures show the ray dot plots in the embodiments of the present invention when the half-field image heights are 0, 0.707, and 1.0. As can be seen from the figures, the root mean square radius of the dot plots in each field of view is smaller than the chip pixel size of 7.6 μm.

[0145] Figure 4 The figure shows the MTF curves of the image transfer function at different fields of view in the embodiment of the present invention. The MTF values ​​of each field of view below 100 lp / mm are all greater than 0.5, and the curves are smooth and compact, indicating that the projection lens produces clear and uniform images and matches well with the 0.45-inch chip.

[0146] Figure 5This is a field curvature and distortion diagram of the projection lens in an embodiment of the present invention. It can be seen from the diagram that the field curvature of the lens is less than 0.1 mm and the distortion is less than 0.2%.

[0147] This invention provides a low-distortion telecentric projection lens for 3D structured light, which features high definition, low distortion, simple structure, easy processing, and low cost.

[0148] The projection lens of this invention has a high system resolution, reaching over 100 lp / mm, and a low system distortion rate, below 0.2%. It uses 7 spherical lenses, has a simple structure, and features low manufacturing cost, low distortion, high resolution, and telecentric image.

[0149] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly referring to the number of technical features indicated. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0150] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood through the specific circumstances.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-distortion telecentric projection lens for 3D structured light, characterized in that, The projection lens comprises, from left to right, a diverging lens group, a stop (4), a converging lens group and an image plane (9); The diverging lens group comprises, from left to right, a first lens (1), a second lens (2) and a third lens (3), and the converging lens group comprises, from left to right, a fourth lens (5), a fifth lens (6), a sixth lens (7) and a seventh lens (8); The first lens (1) is a meniscus lens with its concave surface facing the stop (4), the second lens (2) is a plano-convex lens with its convex surface facing the stop (4), the third lens (3) is a meniscus lens with its concave surface facing away from the stop (4), the fourth lens (5) is a double-concave lens, the fifth lens (6) is a meniscus lens with its concave surface facing the stop (4), the sixth lens (7) is a plano-convex lens with its convex surface facing the image plane (9), and the seventh lens (8) is a meniscus lens with its concave surface facing the image plane (9); The first lens (1) has a negative focal power, the second lens (2) has a positive focal power, the third lens (3) has a positive focal power, the fourth lens (5) has a negative focal power, the fifth lens (6) has a positive focal power, the sixth lens (7) has a positive focal power, and the seventh lens (8) has a positive focal power.

2. A low-distortion telecentric projection lens for 3D structured light according to claim 1, characterized in that, In particular, The distance between the first lens (1) and the second lens (2) is between 3.5 mm and 5.5 mm; The distance between the second lens (2) and the third lens (3) is between 26 mm and 28 mm; The distance between the third lens (3) and the stop (4) is between 0.5 mm and 2.5 mm; The distance between the stop (4) and the fourth lens (5) is between 2.5 mm and 4.5 mm; The distance between the fourth lens (5) and the fifth lens (6) is between 0.5 mm and 2.5 mm; The distance between the fifth lens (6) and the sixth lens (7) is between 0.5 mm and 2.5 mm; The distance between the sixth lens (7) and the seventh lens (8) is between 11 mm and 13 mm; The distance between the seventh lens (8) and the image plane (9) is between 22.5 mm and 24.5 mm.

3. A low-distortion telecentric projection lens for 3D structured light according to claim 2, characterized in that, In particular, The distance between the first lens (1) and the second lens (2) is 4.5 mm; The distance between the second lens (2) and the third lens (3) is 27 mm; The distance between the third lens (3) and the stop (4) is 1.5 mm; The distance between the stop (4) and the fourth lens (5) is 3.5 mm; The distance between the fourth lens (5) and the fifth lens (6) is 1.5 mm; The distance between the fifth lens (6) and the sixth lens (7) is 1.5 mm; The distance between the sixth lens (7) and the seventh lens (8) is 12 mm; The distance between the seventh lens (8) and the image plane (9) is 23.5 mm.

4. A low-distortion telecentric projection lens for 3D structured light according to claim 1, wherein, In particular, The focal length of the first lens (1) is between -45 mm and -55 mm; The focal length of the second lens (2) is between 50 mm and 60 mm; The focal length of the third lens (3) is between 50 mm and 60 mm; The focal length of the fourth lens (5) is between -5 mm and -15 mm; The focal length of the fifth lens (6) is between 30 mm and 40 mm; The focal length of the sixth lens (7) is between 20 mm and 30 mm; The focal length of the seventh lens (8) is between 55 mm and 65 mm.

5. A low-distortion telecentric projection lens for 3D structured light according to claim 4, characterized in that, The focal length of the first lens (1) is -50 mm; The focal length of the second lens (2) is 55 mm; The focal length of the third lens (3) is 55 mm; The focal length of the fourth lens (5) is -10 mm; The focal length of the fifth lens (6) is 35 mm; The focal length of the sixth lens (7) is 25 mm; The focal length of the seventh lens (8) is 60 mm. The refractive index of the first lens (1) is between 1.6 and 1.7; 6. A low-distortion telecentric projection lens for 3D structured light according to claim 1, wherein, The refractive index of the second lens (2) is between 1.7 and 1.8; The refractive index of the third lens (3) is between 1.55 and 1.65; The refractive index of the fourth lens (5) is between 1.7 and 1.8; The refractive index of the fifth lens (6) is between 1.6 and 1.7; The refractive index of the sixth lens (7) is between 1.6 and 1.7; The refractive index of the seventh lens (8) is between 1.6 and 1.

7. The refractive index of the first lens (1) is 1.65; The refractive index of the second lens (2) is 1.75; 7. A low-distortion telecentric projection lens for 3D structured light according to claim 6, characterized in that, The refractive index of the third lens (3) is 1.6; The refractive index of the fourth lens (5) is 1.75; The refractive index of the fifth lens (6) is 1.65; The refractive index of the sixth lens (7) is 1.65; The refractive index of the seventh lens (8) is 1.

65. The effective focal length of the projection lens is 19.5 mm, the relative numerical aperture is effective focal length / 2.4, the maximum aperture is less than 30 mm, and the total optical length is 96.84 mm. ​ ​ 8. A low-distortion telecentric projection lens for 3D structured light according to claim 1, wherein, The chip of the projection lens is 0.45-inch DMD-DLP4500 chip, and the resolution is 912 1140.

9. A low-distortion telecentric projection lens for 3D structured light according to claim 1, wherein, ​

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