Lens for improving laser triangulation ranging precision

Abstract

The embodiment of the invention provides a lens for improving laser triangulation ranging precision. In one specific implementation mode, the lens comprises a first negative meniscus lens with the concave surface side facing the object side, a second negative meniscus lens with the concave surface side facing the object side and a biconvex positive lens which are sequentially arranged from the object side to the image side along the optical axis of the lens; and the first negative meniscus lens and the second negative meniscus lens are glued and fixed. According to the embodiment, the first negative meniscus lens and the second negative meniscus lens are glued and fixed. The first negative meniscus lens and the second negative meniscus lens are glued and fixed to obtain the doublet lens, the lens adopts the design of the doublet lens and the single achromatic biconvex lens, the spherical aberration and the edge distortion of imaging can be effectively reduced, the mass center drift of light spots is inhibited, the size of the light spots is reduced, and the imaging definition is improved; therefore, the measurement precision of the laser triangulation ranging method is better improved.

Description

Technical Field

[0001] This disclosure relates to the field of laser ranging technology. More specifically, it relates to a lens for improving the accuracy of laser triangulation. Background Technology

[0002] Laser triangulation is a high-precision non-contact measurement technique based on geometric trigonometric relationships. It accurately calculates the distance to the object being measured by analyzing the positional changes of the laser reflection spot on the sensor. As a high-precision non-contact measurement technique, it has been widely used in industrial inspection, 3D reconstruction, and other fields. However, traditional laser triangulation systems generally use spherical lenses as receiving lenses. The inherent optical characteristics of spherical lenses cause spherical aberration and edge distortion in the imaging spot. Especially in large-aperture or wide-field-of-view scenarios, the centroid of the spot drifts, directly affecting the ranging accuracy. Furthermore, the spherical lens further amplifies the spot distortion due to surface tilt, curvature changes, or material differences in the object being measured, causing the measurement results to deviate from the true value.

[0003] Existing technologies mostly focus on optimizing mechanical structures, such as using multi-mirror designs or post-processing signal compensation, but fail to eliminate the root causes of aberrations from the source of optical design.

[0004] In addition, traditional methods lack the ability to coordinate chromatic aberration correction for multi-wavelength beams, resulting in significant dispersion effects when imaging with polychromatic light, leading to increased spot size and decreased sharpness. Summary of the Invention

[0005] The purpose of this disclosure is to provide a lens that can simultaneously suppress spherical aberration, distortion, and chromatic aberration to improve the accuracy of laser triangulation, thereby solving at least one of the problems existing in the prior art.

[0006] To achieve the above objectives, the present disclosure adopts the following technical solution: This disclosure provides a lens for improving the accuracy of laser triangulation, comprising: Along the optical axis of the lens, from the object side to the image side, a first negative meniscus lens with its concave side facing the object side, a second negative meniscus lens with its concave side facing the object side, and a biconvex positive lens are arranged sequentially. The first negative meniscus lens and the second negative meniscus lens are glued together and fixed.

[0007] Optionally, the material of the first negative meniscus lens is selected from potassium glass No. 10; the material of the second negative meniscus lens is selected from fluorophosphate glass No. 52; and the material of the biconvex positive lens is selected from lanthanide fluorophosphate glass No. 68.

[0008] Optionally, the surfaces of the first negative meniscus lens, the second negative meniscus lens, and the biconvex positive lens are all standard spherical surfaces.

[0009] Optionally, the effective focal length of the lens is in the range of 100mm to 101mm, and its total optical length is in the range of 125mm to 126mm.

[0010] Optionally, the radius of curvature on the concave side of the first negative meniscus lens ranges from -55mm to -54mm, and the radius of curvature on the convex side ranges from -32mm to -31mm.

[0011] Optionally, the radius of curvature on the concave side of the second negative meniscus lens ranges from -31mm to -30mm, and the radius of curvature on the convex side ranges from -55mm to -54mm.

[0012] Optionally, the radius of curvature of the object-side convex surface of the biconvex positive lens ranges from 91mm to 92mm, and the radius of curvature of the image-side convex surface ranges from 911mm to 92mm.

[0013] Optionally, the thickness of the first negative meniscus lens ranges from 7mm to 8mm, the thickness of the second negative meniscus lens ranges from 3.15mm to 3.65mm, and the thickness of the biconvex positive lens ranges from 5.4mm to 6.6mm.

[0014] Optionally, the distance between the second negative meniscus lens and the biconvex positive lens is in the range of 1.8mm to 2.2mm.

[0015] Optionally, the aperture range of the first negative meniscus lens, the aperture range of the second negative meniscus lens, and the aperture range of the third positive lens are 9.5mm to 10.5mm, respectively.

[0016] The beneficial effects of this disclosure are as follows: The first negative meniscus lens and the second negative meniscus lens are cemented together. This invention achieves a cemented doublet lens by cementing the first and second negative meniscus lenses together. By employing a cemented doublet lens and a single achromatic biconvex lens design, the lens effectively reduces spherical aberration and edge distortion, suppresses spot centroid drift, reduces spot size, and improves image clarity, thereby enhancing the measurement accuracy of the laser triangulation method.

[0017] This invention achieves a multi-level aberration compensation mechanism by cementing two negative meniscus lenses with their concave sides facing the object side to form a cemented doublet lens, and combining it with a biconvex positive lens, thus significantly improving the performance of the laser triangulation system. The first negative meniscus lens handles the main aberration correction, the second negative meniscus lens performs fine-tuning, and the biconvex positive lens provides positive optical power and further reduces spherical aberration. The synergistic operation of these three lenses greatly reduces the system's spherical aberration and decreases the spot size. Attached Figure Description

[0018] The specific embodiments of this disclosure will be described in further detail below with reference to the accompanying drawings.

[0019] Figure 1 A schematic diagram of the structure of a lens for improving the accuracy of laser triangulation provided in an embodiment of this disclosure is shown.

[0020] Figure 2 A dot plot of lens testing provided by an embodiment of this disclosure is shown.

[0021] Figure 3 The diagram shows field curvature and distortion curves for lens testing provided by embodiments of this disclosure.

[0022] Figure 4 The wavefront diagram for lens testing provided by an embodiment of this disclosure is shown.

[0023] Figure 5 The central field-of-view MTF plot for lens testing provided by an embodiment of this disclosure is shown. Detailed Implementation

[0024] To more clearly illustrate this disclosure, the following description, in conjunction with embodiments and accompanying drawings, provides further insight. Similar components in the drawings are indicated by the same reference numerals. Those skilled in the art should understand that the specific description below is illustrative rather than restrictive and should not be construed as limiting the scope of protection of this disclosure.

[0025] The first embodiment of the present invention provides a lens for improving the accuracy of laser triangulation, such as... Figure 1 As shown, it includes: Along the optical axis of the lens, from the object side to the image side, a first negative meniscus lens 1 with its concave side facing the object side, a second negative meniscus lens 2 with its concave side facing the object side, and a biconvex positive lens 3 are arranged sequentially. The first negative meniscus lens 1 and the second negative meniscus lens 2 are glued together and fixed.

[0026] This invention obtains a cemented doublet lens by cementing and fixing a first negative meniscus lens 1 and a second negative meniscus lens 2. By adopting the design of a cemented doublet lens and a single achromatic biconvex lens, the lens can effectively reduce spherical aberration and edge distortion, suppress the centroid drift of the light spot, reduce the light spot size and improve the image clarity, thereby better improving the measurement accuracy of the laser triangulation method.

[0027] This invention achieves a multi-level aberration compensation mechanism by cementing two negative meniscus lenses with their concave sides facing the object side to form a cemented doublet lens, and combining it with a biconvex positive lens 3, thus significantly improving the performance of the laser triangulation system. The first negative meniscus lens 1 handles the main aberration correction, the second negative meniscus lens 2 performs fine-tuning, and the biconvex positive lens 3 provides positive optical power and further reduces spherical aberration. The synergistic operation of these three lenses greatly reduces the system's spherical aberration and decreases the spot size.

[0028] The working principle of the lens system of the present invention is as follows: the incident light beam is diverged by the first negative meniscus lens 1, and then the divergence state of the light beam is further adjusted by the second negative meniscus lens 2. Finally, the double convex positive lens achieves precise focusing, forming a stable optical path system.

[0029] Specifically, when the laser beam enters the lens from the object side along the optical axis, the first negative meniscus lens 1 initially diverges the incident light, forming an appropriate divergence angle. Subsequently, the second negative meniscus lens 2 finely adjusts the diverged beam, optimizing its distribution. The biconvex positive lens 3 then refocuses the beam after the two adjustments, ensuring the reflected spot forms a clear and stable imaging point on the sensor. This optical path design, through a multi-stage beam control mechanism, effectively suppresses spot centroid drift, reduces spot size, and improves imaging clarity, thereby significantly enhancing the accuracy and reliability of laser triangulation.

[0030] In a specific example, a negative meniscus lens consists of a convex surface and a concave surface, and is crescent-shaped overall, with its center thickness being less than its edge thickness; the radius of curvature of the concave surface is smaller than that of the convex surface, which causes the light to diverge.

[0031] In a specific example, the biconvex positive lens 3 consists of two convex surfaces and is mainly used to converge light rays.

[0032] In a specific example, the adhesive used to bond and fix the first negative meniscus lens 1 and the second negative meniscus lens 2 is preferably an optical epoxy resin adhesive, which has good refractive index matching, high light transmittance and moderate mechanical strength.

[0033] In one possible implementation, the material of the first negative meniscus lens 1 is selected from potassium glass No. 10; the material of the second negative meniscus lens 2 is selected from fluorophosphate glass No. 52; and the material of the biconvex positive lens 3 is selected from lanthanide fluorophosphate glass No. 68.

[0034] In a specific example, Potassium Glass 10 specifically refers to High-refractive-index Potassium Glass 10 (H-ZK10), which is a high-refractive-index optical glass with a refractive index of 1.62210 and an Abbe number of 56.71.

[0035] Fluorophosphate glass No. 52 specifically refers to High-refractive-index Fluorophosphate Glass 52 (H-ZF52), an optical glass with an extremely high refractive index and a low Abbe number of 1.847 and an Abbe number of only 23.79. Its low Abbe number makes it an ideal choice for correcting chromatic aberration in positive lenses. Lanthanide fluorophosphate glass No. 68 specifically refers to High-refractive-index Lanthanum Fluorophosphate Glass 68 (H-ZLaF68), a lanthanide optical glass with a high refractive index and high dispersion of 1.88300 and an Abbe number of 40.79.

[0036] In this embodiment, H- in the above material names stands for High-refractive-index, ZK, ZF and ZLaF represent different glass series, namely potassium-based, fluorophosphate-based and lanthanide-based fluorophosphate-based, and the numbers represent specific grades.

[0037] In the above example, the material combination used in the first negative meniscus lens 1, the second negative meniscus lens 2, and the biconvex positive lens 3 can effectively correct chromatic aberration and spherical aberration while maintaining the compactness of the system.

[0038] In this embodiment, the negative lens is typically made of a low Abbe number material, while the positive lens is made of a high Abbe number material. This combination achieves chromatic aberration complementarity and improves the overall imaging quality.

[0039] In one possible implementation, the surfaces of the first negative meniscus lens 1, the second negative meniscus lens 2, and the biconvex positive lens 3 are all standard spherical surfaces. In this embodiment, all lenses, including the surfaces of the first negative meniscus lens 1, the second negative meniscus lens 2, and the biconvex positive lens 3, are made of standard spherical surfaces, which greatly reduces manufacturing costs and processing difficulty while ensuring performance.

[0040] In one possible implementation, the effective focal length of the lens is in the range of 100mm to 101mm, and its total optical length is in the range of 125mm to 126mm.

[0041] In a specific example, preferably, the effective focal length of the lens is 100.0325 mm, and the total optical length is 125.6714 mm. In this embodiment, the effective focal length refers to the distance from the optical rear principal point of the lens to its focal point, which is the distance required to focus parallel light rays into a single point in the projection lens. The total optical length refers to the distance between the object-side surface and the image plane of the first negative meniscus lens 11 of the lens. The lens of the present invention preferably has an effective focal length of 100.0325 mm and a total optical length of 125.6714 mm. Through precise optical power allocation and synergistic optimization of the negative meniscus lens and the biconvex positive lens 3, a compact structure and high imaging accuracy are achieved while ensuring good aberration correction. It has excellent environmental adaptability and energy utilization, significantly improving the measurement accuracy, stability, and miniaturization level of the laser triangulation system. Compared with traditional designs, it has significant improvements in focal length accuracy, size, and imaging quality.

[0042] In one possible implementation, the radius of curvature of the concave side of the first negative meniscus lens 1 ranges from -55mm to -54mm, and the radius of curvature of its convex side ranges from -32mm to -31mm.

[0043] The concave side radius of curvature of the second negative meniscus lens 2 ranges from -31mm to -30mm, and the convex side radius of curvature ranges from -55mm to -54mm.

[0044] The object-side convex surface of the biconvex positive lens 3 has a radius of curvature ranging from 91mm to 92mm, and the image-side convex surface has a radius of curvature ranging from 911mm to 92mm.

[0045] In a specific example, the object-side radius of curvature of the first negative meniscus lens 11 is -54.600 mm, and the image-side radius of curvature of the first negative meniscus lens 11 is -31.700 mm; the object-side radius of curvature of the second negative meniscus lens 22 is -31.700 mm, and the image-side radius of curvature of the second negative meniscus lens 22 is -54.800 mm; the object-side radius of curvature of the biconvex positive lens 33 is 91.500 mm, and the image-side radius of curvature of the biconvex positive lens 33 is -631.705 mm.

[0046] In a specific example, the first negative meniscus lens 1 and the second meniscus lens are mirror-symmetrical. The symmetrical design of the cemented doublet lens combined with the asymmetrical curvature of the biconvex positive lens 3 achieves efficient aberration compensation and precise focal length control, significantly improving the measurement accuracy and stability of the laser triangulation system. Specifically, the mirror-symmetrical design of the first negative meniscus lens 1 and the second negative meniscus lens 2, through precise matching of the curvature radii of the two lenses, achieves mutual aberration compensation and dynamic balance of focal length, significantly reducing spherical aberration and coma while maintaining stable optical power, thus greatly improving the measurement accuracy of the laser triangulation system.

[0047] In one possible implementation, the thickness of the first negative meniscus lens 1 ranges from 7mm to 8mm, the thickness of the second negative meniscus lens 2 ranges from 3.15mm to 3.65mm, and the thickness of the biconvex positive lens 3 ranges from 5.4mm to 6.6mm.

[0048] In one possible implementation, the distance between the second negative meniscus lens 2 and the biconvex positive lens 3 is in the range of 1.8 mm to 2.2 mm.

[0049] In one possible implementation, the aperture range of the first negative meniscus lens 1, the aperture range of the second negative meniscus lens 2, and the aperture range of the third positive lens are 9.5mm to 10.5mm, respectively.

[0050] In a specific example, the thickness of the first negative meniscus lens 1 is 7.500 mm; the thickness of the second negative meniscus lens 2 is 3.500 mm; the distance from the image-side surface of the second negative meniscus lens 2 to the object-side surface of the biconvex positive lens 3 is 2.000 mm; the thickness of the biconvex positive lens 3 is 6.000 mm; and the distance between the biconvex positive lens 3 and the image plane is 106.671 mm. In this embodiment, lens thickness refers to the distance between the two optical surfaces of the lens along the optical axis. In this embodiment, by precisely controlling the thicknesses of the first negative meniscus lens 1, the second negative meniscus lens 2, and the biconvex positive lens 3, as well as the key spacing and imaging distance of the lens components, the lens achieves multi-level aberration compensation and dynamic optical power, significantly improving the measurement accuracy, optical path stability, and environmental adaptability of the laser triangulation system.

[0051] The test results for the lens in this embodiment are as follows: Reference Figure 2 The dot plot shows that the lens has reached the diffraction limit in each field of view. The experiment yielded an allegro radius of 5.733 μm. The root mean square radius (RMS) of the spot in each field of view is less than 5 μm; specifically, the RMS radius of field of view one is 1.906 μm, the RMS radius of field of view two is 2.994 μm, and the RMS radius of field of view three is 3.891 μm, which significantly improves resolution and sharpness. In this embodiment, the RMS of the spot is a core parameter in the optical system for measuring the degree of light dispersion on the image plane. It quantifies the deviation between the actual optical system and the ideal image using statistical methods. The smaller the value, the more concentrated the light and the clearer the image, making it a key indicator for evaluating the performance of the optical system.

[0052] The field curvature and distortion in this embodiment can be seen from... Figure 3As can be seen from the figure, the field curvature has a relatively small impact on the lens. The experiment shows that the distortion of the lens's maximum field of view is 0.0076%, which is much less than 1%, meeting the actual imaging quality requirements.

[0053] Reference Figure 4 The experiment showed that the RMS value of this lens was optimized to 0.0384λ (λ=587.6nm), which is much smaller than λ / 4, thus meeting the requirements for diffraction-limited imaging.

[0054] Reference Figure 5 As can be seen from the figure, at 30 lp / mm, the center field modulation transfer function (MTF) is >0.75, and the edge field is >0.65, indicating that high-frequency details are well preserved and the imaging is clear.

[0055] In the description of this disclosure, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this disclosure 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 this disclosure. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly, for example, they can be fixed connections, detachable connections, or integral connections; they can be mechanical connections or electrical connections; they can be direct connections or indirect connections through an intermediate medium; they can be internal connections between two elements. For those skilled in the art, the specific meaning of the above terms in this disclosure can be understood according to the specific circumstances.

[0056] It should also be noted that, in the description of this disclosure, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0057] Obviously, the above embodiments of this disclosure are merely examples for clearly illustrating this disclosure, and are not intended to limit the implementation of this disclosure. For those skilled in the art, other variations or modifications can be made based on the above description. It is impossible to exhaustively list all implementation methods here. Any obvious variations or modifications derived from the technical solutions of this disclosure are still within the protection scope of this disclosure.

Claims

1. A lens for improving the accuracy of laser triangulation, characterized in that, include: Along the optical axis of the lens, from the object side to the image side, a first negative meniscus lens with its concave side facing the object side, a second negative meniscus lens with its concave side facing the object side, and a biconvex positive lens are arranged sequentially. The first negative meniscus lens and the second negative meniscus lens are glued together and fixed.

2. The lens according to claim 1, characterized in that, The first negative meniscus lens is made of potassium glass No. 10; the second negative meniscus lens is made of fluorophosphate glass No. 52; and the biconvex positive lens is made of lanthanide fluorophosphate glass No.

68.

3. The lens according to claim 1, characterized in that, The surfaces of the first negative meniscus lens, the second negative meniscus lens, and the biconvex positive lens are all standard spherical surfaces.

4. The lens according to claim 1, characterized in that, The effective focal length of the lens is 100mm to 101mm, and its total optical length is 125mm to 126mm.

5. The lens according to claim 1, characterized in that, The radius of curvature on the concave side of the first negative meniscus lens ranges from -55mm to -54mm, and the radius of curvature on the convex side ranges from -32mm to -31mm.

6. The lens according to claim 5, characterized in that, The radius of curvature on the concave side of the second negative meniscus lens ranges from -31mm to -30mm, and the radius of curvature on the convex side ranges from -55mm to -54mm.

7. The lens according to claim 6, characterized in that, The object-side convex surface of the biconvex positive lens has a radius of curvature ranging from 91 mm to 92 mm, and the image-side convex surface has a radius of curvature ranging from 911 mm to 92 mm.

8. The lens according to claim 1, characterized in that, The thickness of the first negative meniscus lens ranges from 7mm to 8mm, the thickness of the second negative meniscus lens ranges from 3.15mm to 3.65mm, and the thickness of the biconvex positive lens ranges from 5.4mm to 6.6mm.

9. The lens according to claim 1, characterized in that, The distance between the second negative meniscus lens and the biconvex positive lens ranges from 1.8 mm to 2.2 mm.

10. The lens according to claim 1, characterized in that, The aperture range of the first negative meniscus lens, the aperture range of the second negative meniscus lens, and the aperture range of the third positive lens are 9.5mm to 10.5mm, respectively.

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